What are 'good' carbs?

Not all carbs are created equal and some are healthier than others. Carbohydrates found in plant-based foods – complex carbs – are ‘good’ carbs, and are often packed with nutrients, such as bran and fiber that can help to improve your digestion and support metabolism.

“To reap the benefits of carbohydrates, try opting for carbs loaded with nutrients, such as wholegrains and fruit and vegetables; these are complex carbohydrates or ‘good’ carbs,” says Oddy.

Some examples of good carbs include:

• Oats
• Quinoa
• Whole fruit
• Sweet potatoes (ideally with the skin)
• Beets
• Yogurt
• Bananas
• Carrots
• Nuts and seeds
• Brown rice
• Whole grain bread
• Legumes (beans, peas, lentils, soybeans and peanuts)

What are 'bad' carbs?

Simple or ‘bad’ carbs (also known as refined or processed carbs) are sugars, broken down quickly and used as energy, says Oddy. 

During processing, the bran and germ of the whole grain are removed, which also removes fiber, vitamins, minerals and antioxidants, meaning these foods have little nutritional value.

“These types of carbs often get labeled bad but not all simple carbs are unhealthy. Some whole fruits and milk are composed of simple carbs, but still contain a variety of healthy nutrients,” says Oddy.

Examples of bad carbs include:

• White bread
• Pizza dough
• Pastries
• White pasta
• Beer
• Fruit juice
• Sugary sodas
• Pancakes
• Tomato sauce
• Cake
• Pretzels

What's the difference between good and bad carbs?

According to Oddy: “Choosing a variety of complex carbohydrates each day is brilliant for feeding the gut microbiome, promoting a healthy digestive system.

“These complex carbs will also have a lesser impact on blood sugar levels, which is particularly important for those with diabetes or polycystic ovary syndrome (PCOS). 

Stable blood sugar levels will keep your energy and mood stable throughout the day, too.

“On the other hand, recent studies show that people who regularly consume foods containing low-quality, simple carbohydrates have an increased risk of chronic disease, such as diabetes and cardiovascular disease,” she says.

Eating too little or too many carbs can be equally unhealthy, too, and is associated with increased mortality, a study published in the Lancet found. 

Should you avoid simple carbohydrates?

It’s important to note that not all simple carbohydrates are ‘unhealthy’ choices, adds Oddy. 

“Simple carbs are present in many nutrient-rich foods, such as fruits and milk. The simple carbs to be mindful of are processed foods or foods with added sugars. Enjoying all foods and meals in moderation is normal and healthy – and key for physical and emotional wellbeing. The key word here is moderation. In my clinic, we try to remove labeling foods and remove the idea that certain foods or meals are inherently ‘bad’.”

This article is for informational purposes only and is not meant to offer medical advice.

Carbohydrates are the sugars, starches and fibers found in fruits, grains, vegetables and milk products, according to the UK’s National Health Service (NHS). Though often maligned in trendy diets, carbohydrates — one of the basic food groups — are important to a healthy diet.

"Carbohydrates are macronutrients, meaning they are one of the three main ways the body obtains energy, or calories," said Paige Smathers, a Utah-based registered dietitian. The American Diabetes Association notes that carbohydrates are the body's main source of energy. They are called carbohydrates because, at the chemical level, they contain carbon, hydrogen and oxygen.

There are three macronutrients: carbohydrates, protein and fats, Smathers said. Macronutrients are essential for proper body functioning, and the body requires large amounts of them. All macronutrients must be obtained through diet; the body cannot produce macronutrients on its own.

Related: Digestive system: facts, function & diseases

The recommended daily amount (RDA) of carbs for adults is around 4.7 ounces (135 grams), according to the National Institutes of Health (NIH); however, the NIH also recommends that everyone should have his or her own carbohydrate goal. Carb intake for most people should be between 45% and 65% of total calories. One gram of carbohydrates equals about 4 calories, so a diet of 1,800 calories per day would equal about 202 grams on the low end and 292 grams of carbs on the high end. However, people with diabetes should not eat more than 200 grams of carbs per day, while pregnant women need at least 175 grams, according to the NIH.

Why are carbohydrates important?

Carbohydrates provide fuel for the central nervous system and energy for working muscles. They also prevent protein from being used as an energy source and enable fat metabolism, according to the NHS.

Also, "carbohydrates are important for brain function," Smathers said. They are an influence on "mood, memory, etc., as well as a quick energy source." In fact, the RDA of carbohydrates is based on the amount of carbs the brain needs to function.

Two 2017 studies published in the journal Proceedings of the National Academy of Sciences have also linked carbs to decision-making. In the studies, people who ate a high-carbohydrate breakfast were less willing to share when playing the "ultimatum game" than those who ate high-protein breakfasts. Scientists speculate this may be caused by baseline dopamine levels, which are higher after eating carbohydrates. This doesn't mean carbs make you mean, but underscores how different types of food intake can affect cognition and behavior. 

Simple vs. complex carbohydrates

Carbohydrates are classified as simple or complex, Smathers said. The difference between the two forms is the chemical structure and how quickly the sugar is absorbed and digested. Generally speaking, simple carbs are digested and absorbed more quickly and easily than complex carbs, according to the NIH.

Simple carbohydrates contain just one or two sugars, such as fructose (found in fruits) and galactose (found in milk products). These single sugars are called monosaccharides. Carbs with two sugars — such as sucrose (table sugar), lactose (from dairy) and maltose (found in beer and some vegetables) — are called disaccharides, according to the NIH.

Simple carbs are also in candy, soda and syrups. However, these foods are made with processed and refined sugars and do not have vitamins, minerals or fiber. They are called "empty calories" and can lead to weight gain, according to the NIH.

Complex carbohydrates (polysaccharides) have three or more sugars. They are often referred to as starchy foods and include beans, peas, lentils, peanuts, potatoes, corn, parsnips, whole-grain breads and cereals.

Smathers pointed out that, while all carbohydrates function as relatively quick energy sources, simple carbs cause bursts of energy much more quickly than complex carbs because of the quicker rate at which they are digested and absorbed. Simple carbs can lead to spikes in blood sugar levels and sugar highs, while complex carbs provide more sustained energy.

Smathers offered the following advice: "It's best to focus on getting primarily complex carbs in your diet, including whole grains and vegetables."

What are the different types of carbohydrates?

In the body, carbs break down into smaller units of sugar, such as glucose and fructose, according to the American Heart Association. The small intestine absorbs these smaller units, which then enter the bloodstream and travel to the liver. The liver converts all of these sugars into glucose, which is carried through the bloodstream — accompanied by insulin — and converted into energy for basic body functioning and physical activity, according to the journal Nutrients.

If the glucose is not immediately needed for energy, the body can store up to 2,000 calories of it in the liver and skeletal muscles in the form of glycogen, according to the University of Nebraska. Once glycogen stores are full, carbs are stored as fat. If you have insufficient carbohydrate intake or stores, the body will consume protein for fuel. This is problematic because the body needs protein to make muscles. Using protein instead of carbohydrates for fuel also puts stress on the kidneys, leading to the passage of painful byproducts in the urine.

Fiber is essential to digestion. Fibers promote healthy bowel movements and decrease the risk of chronic diseases such as coronary heart disease and diabetes, according to Harvard Medical School. However, unlike sugars and starches, fibers are not absorbed in the small intestine and are not converted to glucose. Instead, they pass into the large intestine relatively intact, where they are converted to hydrogen and carbon dioxide and fatty acids. - The NHS recommends that people consume up to 30 grams of fiber per day as part of a balanced diet. Sources of fiber include fruits, grains and vegetables, especially legumes.

Related: Gestational diabetes: Symptoms, diagnosis & complications

Smathers pointed out that carbs are also found naturally in some forms of dairy and both starchy and non-starchy vegetables. For example, non-starchy vegetables like lettuces, kale, green beans, celery, carrots and broccoli all contain carbs. Starchy vegetables like potatoes and corn also contain carbohydrates, but in larger amounts. According to the American Diabetes Association, non-starchy vegetables generally contain only about 5 grams of carbohydrates per cup of raw vegetables, and most of those carbs come from fiber.

What’s the difference between good and bad carbohydrates?

Carbohydrates are found in foods you know are good for you (vegetables) and ones you know are not (doughnuts). This has led to the idea that some carbs are "good" and some are "bad." As Live Science has previously reported, carbs commonly considered bad include pastries, sodas, highly processed foods, white rice, white bread and other white-flour foods. These are foods with simple carbs. Bad carbs rarely have any nutritional value.

Carbs usually considered good are complex carbs, such as whole grains, fruits, vegetables, beans and legumes. These are not only processed more slowly, but they also contain a bounty of other nutrients.

The Pritikin Longevity Center offers this checklist for determining if a carbohydrate is "good" or "bad."

Good carbs are:

• Low or moderate in calories
• High in nutrients
• Devoid of refined sugars and refined grains
• High in naturally occurring fiber
• Low in sodium
• Low in saturated fat
• Very low in, or devoid of, cholesterol and trans fats

Bad carbs are:

• High in calories
• Full of refined sugars, like corn syrup, white sugar, honey and fruit juices
• High in refined grains like white flour
• Low in many nutrients
• Low in fiber
• High in sodium
• Sometimes high in saturated fat
• Sometimes high in cholesterol and trans fats

Glycemic index

Recently, nutritionists have said that it's not the type of carbohydrate, but rather the carb's glycemic index that's important. The glycemic index measures how quickly and how much a carbohydrate raises blood sugar.

High-glycemic foods like pastries raise blood sugar highly and rapidly; low-glycemic foods raise it gently and to a lesser degree. Some research has linked high-glycemic foods with diabetes, obesity, heart disease and certain cancers, according to Harvard Medical School. 

A global study published in the New England Journal of Medicine, found that poor-quality carbohydrates (high-glycemic diet) lead to higher risks of heart attacks and strokes. In total 137,851 people were surveyed to establish their glycemic index and the glycemic load (amount of carbs multiplied by its glycemic index) of their diets. The results of the study found that the participants who were placed in the top 20% of all recorded glycemic index, were 50% more likely to have a cardiovascular attack or stroke if they had a pre-existing heart condition. Those without a pre-existing condition increased their risk by 20%. During the studies follow-up period, there were 8,780 deaths and 8,252 participants had at least one major cardiovascular event.  

On the other hand, recent research suggests that following a low-glycemic diet may not actually be helpful. A 2014 study published in JAMA found that overweight adults eating a balanced diet did not see much additional improvement on a low-calorie, low-glycemic index diet. Scientists measured insulin sensitivity, systolic blood pressure, LDL cholesterol and HDL cholesterol and saw that the low-glycemic diet did not improve them. It did however, lower triglycerides - a type of fat that can be found in the blood and in high quantities - increases the risk of heart disease, according to the cholesterol charity Heart UK. 

Carbohydrate benefits

What are the benefits of carbohydrates?

The right kind of carbs can be incredibly good for you. Not only are they necessary for your health, but they carry a variety of added benefits.

Mental health

Carbohydrates may be important to mental health. A study published in 2009 in the journal JAMA Internal Medicine found that people on a high-fat, low-carb diet for a year had more anxiety, depression and anger than people on a low-fat, high-carb diet. Scientists suspect that carbohydrates help with the production of serotonin in the brain.

Carbs may help memory, too. A 2008 study at Tufts University had overweight women cut carbs entirely from their diets for one week. Then, they tested the women's cognitive skills, visual attention and spatial memory. The women on no-carb diets did worse than overweight women on low-calorie diets that contained a healthy amount of carbohydrates.

Weight loss

Though carbs are often blamed for weight gain, the right kind of carbs can actually help you lose and maintain a healthy weight. This happens because many good carbohydrates, especially whole grains and vegetables with skin, contain fiber, according to the NHS. 

A study published in the Journal of Nutrition in 2009 followed middle-age women for 20 months and found that participants who ate more fiber lost weight, while those who decreased their fiber intake gained weight. Another recent study linked fat loss with low-fat diets, not low-carb ones.

While some studies have found that low-carb diets do help people lose weight, a meta analysis conducted in 2015 and published in The Lancet found that when viewed long term, low-fat and low-carb diets had similar success rates. People lost more weight early on while on low-carb diets but after a year they were all in similar places.

Good source of nutrients

Whole, unprocessed fruits and vegetables are well known for their nutrient content. Some are even considered superfoods because of it — and all of these leafy greens, bright sweet potatoes, juicy berries, tangy citruses and crunchy apples contain carbs.

One important, plentiful source of good carbs is whole grains. A large study published in 2010 in the Journal of the American Dietetic Association found that those eating the most whole grains had significantly higher amounts of fiber, energy and polyunsaturated fats, as well as all micronutrients (except vitamin B12 and sodium). An additional study, published in 2014 in the journal Critical Reviews in Food Science and Nutrition, found that whole grains contain antioxidants, which were previously thought to exist almost exclusively in fruits and vegetables.

Heart health

Fiber also helps to lower cholesterol, said Kelly Toups, a registered dietitian with the Whole Grains Council. The digestive process requires bile acids, which are made partly with cholesterol. As your digestion improves, the liver pulls cholesterol from the blood to create more bile acid, thereby reducing the amount of LDL, the "bad" cholesterol.

Toups referenced a study in the American Journal of Clinical Nutrition that looked at the effect of whole grains on patients taking cholesterol-lowering medications called statins. Those who ate more than 16 grams of whole grains daily had lower bad-cholesterol levels than those who took the statins without eating the whole grains.

Carbohydrate deficiency

Not getting enough carbs can cause problems. Without sufficient fuel, the body gets no energy. Additionally, without sufficient glucose, the central nervous system suffers, which may cause dizziness or mental and physical weakness, according to the NHS. A deficiency of glucose, or low blood sugar, is called hypoglycemia.

If the body has insufficient carbohydrate intake or stores, it will consume protein for fuel. This is problematic because the body needs protein to make muscles. Using protein for fuel instead of carbohydrates also puts stress on the kidneys, leading to the passage of painful byproducts in the urine, according to the University of Cincinnati.

People who don't consume enough carbohydrates may also suffer from insufficient fiber, which can cause digestive problems and constipation.

Additional resources

• American Diabetes Association: Understanding Carbohydrates
• Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating
• Human Metabolism: A Regulatory Perspective

Keeping weight off may be about more than just "calories in and calories out": Some diets may be better calorie-burners than others, a new study suggests.

The study, which involved people trying to maintain weight loss, found that participants burned more calories on a low-carb diet than a high-carb diet. Specifically, among participants with the same average body weight, those who ate a low-carb diet burned about 250 more calories a day than those on the high-carb diet, while engaging in similar levels of physical activity.

The findings, which are published today (Nov. 14) in the journal The BMJ, suggest that low-carb diets may help people keep weight off over the long term, a notoriously difficult feat.

"The type of calories you consume affect the number of calories you burn," David Ludwig, co-principal investigator of the study and co-director of the Boston Children's Hospital's New Balance Foundation Obesity Prevention Center, told Live Science. "These novel effects of food, beyond calorie content, may help make long-term weight control easier and more effective." [7 Tips for Moving Toward a More Plant-Based Diet]

However, some experts say it's too soon to recommend that the public switch to a low-carb diet like the one in the study for weight-loss maintenance, in part because the long-term health effects of such diets are unclear.

"It's too early to really say whether or not this type of low-carb diet is healthy in the long run," said Dana Hunnes, a senior dietitian at the Ronald Reagan UCLA Medical Center in Los Angeles, who was not involved in the study.

The "carbohydrate-insulin" model

The study aimed to test a hypothesis known as the "carbohydrate-insulin model of obesity." According to this idea, processed carbohydrates that have a high-glycemic index lead fat cells to store excess calories rather than burning them. (High-glycemic foods release sugar quickly into the bloodstream.)

However, some short-term studies (typically less than two weeks) have found no difference between high-carb and low-carb diets regarding the number of calories people burn. But the new study aimed to look at this question over a longer period, around five months.

The study involved 164 overweight adults who first underwent a weight-loss regimen in order to lose around 10 percent of their body weight. Then, they were randomly assigned to follow a low-, moderate- or high-carbohydrate diet — with 20, 40 or 60 percent of their calories coming from carbs, respectively — for 20 weeks. The low-carb group also consumed a higher amount of fat, but all groups consumed about the same amount of protein, sodium and added sugar. All of the participants were provided with fully prepared meals to ensure they were consuming these precise levels of nutrients.

The researchers also adjusted each participant's calorie intake so that they would maintain their current weight, and not gain or lose weight. The researchers then measured the participants' metabolic rate, or how many calories they were burning throughout the day. Participants also wore accelerometers to measure their level of physical activity.

When the researchers compared the calories burned by participants who weighed the same, they found that those on the low-carb diet burned 209 to 278 calories more per day than those on the high-carb diet.

If this difference persisted over time, it would translate to about a 20-pound weight loss over three years, without a change in calorie intake, the researchers said.

The effect was greatest among participants who naturally tended to secrete high levels of insulin after consuming glucose. (Insulin is a hormone that helps get sugar, or glucose, from the bloodstream into cells). Among these participants, those on the low-carb diet burned around 400 calories more per day than those on the high-carb diet.

This finding is consistent with the carbohydrate-insulin model, the researchers said. The model proposes that a lower- carb diet will lower insulin levels and "produce other beneficial hormone changes that lead fat cells to release their pent- up calories," Ludwig said. "With more calories in the blood — not trapped in fat cells —  the brain and muscle have better access to the fuels they need."

Future studies

Still, the new study cannot prove that the low-carb, high-fat diet alone caused participants to burn more calories. Although the diets were as similar as possible between groups, other dietary factors, such as levels of certain nutrients not accounted for in the study, could have played a role in the effect, the researchers said. So more research is needed to understand why participants in the low-carb group burned more calories.

More studies are also needed to examine how the findings might be applied to weight-loss treatments to help people in a real-world setting.

For example, participants in the study had their meals prepared and precisely adjusted to maintain their weight. But in the real world "we're not adjusting our intake every week or days based on a scientific equation," Hunnes told Live Science, so it's unclear if the results would apply to people who were not following such a precise diet.

And because the study was 20 weeks, the long-term effects of the specific low-carb diet followed in the study — such as risks for heart disease or overall mortality — are not known, Hunnes added. (A recent study found that people who consumed both high- or low-carb diets were at greater risk for early death, compared with those who consumed a moderate-carbohydrate diet.)

Ludwig and colleagues have just started a trial that will look at the effects of three different diets on people's energy expenditure: a very-low carb diet; a high-carb/low-sugar diet; and a high-carb/high-sugar diet.

Originally published on Live Science.

First there was high carb, then there was low carb and now there's … medium carb?

It may not sound as sexy, but eating carbohydrates in moderation may be best for boosting longevity, a large new study suggests.

The study, which involved more than 15,000 Americans who were tracked for a quarter of a century, found that those who ate a low-carb diet (with less than 40 percent of daily calories coming from carbs) or a high-carb diet (with more than 70 percent of daily calories coming from carbs) were more likely to die during the study period, compared with those who ate a moderate-carb diet, with about 50 to 55 percent of their calories coming from carbs.

For example, based on the findings, the researchers estimated that from age 50, people who consumed a moderate-carb diet would have a life expectancy that was about four years longer than those who consumed a very low-carb diet (with an average life expectancy of 83 years for moderate-carb eaters versus 79 years for very low-carb eaters).

But it wasn't all bad news for people following low-carb diets. In the second part of the study, published today (Aug. 16) in the journal The Lancet Public Health, the researchers examined the effect of replacing carbs with either animal-based or plant-based proteins and fats. They found that low-carb diets that involved people consuming animal-based proteins and fats were linked with a greater risk of early death, but low-carb diets that involved people consuming plant-based proteins and fats were linked with a reduced risk of early death. [7 Tips for Moving Toward a More Plant-Based Diet]

"Low-carb diets that replace carbohydrates with protein or fat are gaining widespread popularity as a health and weight loss strategy," lead study author Dr. Sara Seidelmann, a research fellow in cardiovascular medicine at Brigham and Women’s Hospital in Boston, said in a statement. "However, our data suggests that animal-based low carbohydrate diets, which are prevalent in North America and Europe, might be associated with shorter overall life span."

Still, Seidelmann said that "if one chooses to follow a low carbohydrate diet, then exchanging carbohydrates for more plant-based fats and proteins might actually promote healthy ageing in the long term."

Carbs and longevity

Low-carb diets can help people lose weight in the short term, numerous studies have found; but the long-term health effects of the diets are less clear.

In the new study, the researchers examined information from nearly 15,500 adults ages 45 to 64 from four communities in North Carolina, Mississippi, Minnesota and Maryland. At the start of the study in the late 1980s, and again six years later, participants completed surveys about the types of foods they ate and how often.

Participants were followed for about 25 years, during which 6,283 people died.

The researchers found that the link between carb intake and life expectancy was U-shaped; meaning that, during the study, both low- and high-carb diets were linked with a greater risk of death, while moderate-carb diets were linked with a lower risk of death.

The researchers then pulled data from seven other studies, as well as their own study, to perform a separate analysis involving more than 432,000 people in 20 countries. This analysis confirmed the researchers' earlier findings: Low- and high-carb diets were linked with a 20 percent increase in the risk of death during the study, compared with moderate-carb diets.

But the analysis also found that, with low-carb diets, what mattered was the source of proteins and fats. Diets that involved replacing carbs with proteins and fats from animal sources, including beef, lamb, pork, chicken and cheese, were linked with a greater risk of death. In contrast, diets that involved replacing carbs with proteins and fats from plant sources, such as vegetables, legumes and nuts, were tied to a lower risk of death.

Study caveats

The researchers noted that their study only found an association and did not prove that low- or high-carb diets were the cause of the increase in early death risk. What's more, the study only assessed people's diets at two points in time, and it's possible that participants' diets may have changed during the 25-year study, which could have affected the results.

Despite these limitations, a U-shaped link between diet and health outcomes seems logical, because "essential nutrients should be consumed above a minimal level to avoid deficiency, and below a maximal level to avoid toxicity," Dr. Andrew Mente and Dr. Salim Yusuf, both of McMaster University and the Population Health Research Institute in Hamilton, Canada, wrote in a commentary accompanying the study. In other words, a "sweet spot." (Mente and Yusuf were not involved with the new research.)

"On the basis of these principles, moderate intake of carbohydrate … is likely to be more appropriate for the general population than are very low or very high intakes. This would translate to a generally balanced diet that includes fruit, vegetables, legumes, whole grains, nuts, fish, dairy, and unprocessed meats—all in moderation," Mente and Yusuf wrote.

Still, the commentary called for more studies that look at the effect of eating carbs on certain biomarkers; as well as studies that randomly assign people to follow certain dietary patterns, rather than focusing on specific nutrients.

Original article on Live Science.

For some people on a diet, the pounds just seem to fall off, while others have a much harder time losing weight. Now, a new, small study finds that people's gut bacteria may play a role in determining how easy, or difficult, it is for them to lose weight.

The study suggests that, among people who have a hard time losing weight, their gut bacteria tend to be better at using carbohydrates, which provide people's bodies with more energy. This is usually a good thing, as people need energy to fuel their bodies. But for some people trying to lose weight, the ability of their gut bacteria to provide energy may be a weight-loss deterrent, the researchers said.

The study "tells us gut bacteria are likely an important determinant of the degree of weight loss attained following lifestyle and dietary intervention," said Dr. Purna Kashyap, a gastroenterologist at the Mayo Clinic in Rochester, Minnesota, and co-senior author of the study. [5 Ways Gut Bacteria Affect Your Health]

The researchers stressed that the findings are preliminary and need to be confirmed with larger studies. But the study suggests the "need to take the microbiome into account in clinical studies [on weight loss]; and it also provides an important direction to pursue in terms of providing individualized care in obesity," Kashyap told Live Science.

Studying stool

For the new study, the researchers analyzed data from 26 overweight or obese people enrolled in an obesity-treatment program that involved diet, exercise and behavioral changes aimed at helping people lose weight. The researchers also analyzed the participants' stool samples, which were collected at the start of the study and after three months on the weight-loss program.

During this three-month period, the participants lost an average of 8.2 lbs. (3.7 kilograms). Nine of the participants lost at least 5 percent of their body weight, which the researchers considered a "successful" weight loss. The other 17 participants lost less than 5 percent of their body weight. Among the "successful" weight-loss group, participants lost an average of 17.4 lbs. (7.9 kg), compared with 3.3 lbs. (1.5 kg) in the "unsuccessful" group.

Next, using the stool samples, the researchers analyzed the participants' gut microbiome for bacterial genes that play a role in breaking down carbohydrates. They found that, in the unsuccessful weight-loss group, there was an increased number of these bacterial genes, compared with the successful weight- loss group. [5 Things Your Poop Says About Your Health]

"A gut microbiota with increased capability for carbohydrate metabolism appears to be associated with decreased weight loss," the researchers wrote in the study, published online today (Aug. 1) in the journal Mayo Clinic Proceedings.

What's more, the study also found that people in the successful weight-loss group had higher amounts of a bacterium called Phascolarctobacterium, while those in the unsuccessful weight-loss group had higher amounts of a bacterium called Dialister. (Still, it's unclear whether Dialister bacteria specifically use carbohydrates in a way that could hinder weight loss, the researchers noted.)

Future avenues

The new study is "supportive of things we're learning about the microbiome," said Dr. Vijaya Surampudi, a physician with the Risk Factor Obesity Weight Management Program at UCLA Health who was not involved in the study.

Indeed, the findings agree with other recent studies that suggest gut bacteria may play a role in obesity and weight loss. For example, a 2013 study in mice found that mice who received a "gut bacteria transplant" from an obese human gained more weight and fat mass than those who received bacteria from a lean human. And a 2015 study in people found that bariatric surgery may lead to long-term changes in people's gut bacteria that could contribute to weight loss.

However, Surampudi agreed that the new study was small, and that more research is needed to confirm the findings.

One day, it might be possible to identify people who would respond, or not, to a given diet, Surampudi said. For example, if the new findings turn out to be true, it may mean that people who have more carbohydrate-using bacteria would respond better to a low-carb diet, she said.

"We [could] use the microbiome to help us navigate which diet approach would be better for people," Surampudi told Live Science, though more research is needed before this approach could be used in patients.

Kashyap agreed that if future studies confirm the findings, "we may need to modify [a person's] the weight loss plan based on an individual's gut bacteria; or try to change the makeup of the gut bacteria using targeted approaches like probiotics before instituting a weight loss program."

Original article on Live Science.

Pasta lovers had reason to celebrate yesterday, as headlines declared that the often-demonized carbohydrate could "help you lose weight." But is this mainstay of Italian cuisine really good for your waistline?

The headlines were referring to a new meta-analysis, published yesterday (April 3) in the journal BMJ Open, that found that eating pasta was not linked with weight gain when it was consumed as part of a "low-glycemic-index" diet. (Foods that have a low glycemic index release sugar slowly into the bloodstream. Pasta has a relatively low glycemic index compared with other refined grains, such as white bread.)

The researchers analyzed data from 29 studies with a total of nearly 2,500 people who either consumed pasta as part of a low-glycemic diet or ate other carbohydrates that had a higher glycemic index. After about 12 weeks, those in the pasta groups lost, on average, about half a kilogram, or 1.1 lbs., compared with the groups that ate the other carbohydrates.

But the new findings are not an invitation to gorge on pasta. For one thing, the people in the pasta groups certainly weren't doing so. Instead, they had, on average, 3.3 servings of pasta each week — and one serving was equal to about one-half cup of cooked pasta.

In addition, the researchers stressed that the findings apply only to pasta eaten in the context of a low-glycemic-index diet. Whether the new findings "will hold in the context of other healthy dietary patterns, such as Mediterranean and vegetarian dietary patterns, is unclear," the researchers wrote in their paper. [9 Snack Foods: Healthy or Not?]

What's more, the researchers noted that the amount of weight loss seen in the study was small and that it's unclear if people would keep this weight off over the long term.

Heather Mangieri, a registered dietitian and nutrition consultant in Pittsburgh, who was not involved in the study, said that the results did not surprise her. Although pasta and other carbohydrates have a "bad reputation," these foods can still have a place on your plate, she said.

"If your pasta is portioned properly and paired with a nutrient-rich vegetable and a lean protein, it can be a very healthy option," Mangieri told Live Science. (A proper portion of pasta is is about one-half cup to one cup, she added.)

But people need to be careful when they combine pasta with items like rich sauces, she said.

"Think about it — how many people eat pasta alone?" Mangieri said. "The calorie count climbs quickly when your pasta is covered with creamy sauces and eaten with high-fat meatballs and garlic bread."

So, when people eat pasta, they should keep in mind the glycemic index and calorie count of the other foods they add to it, she said.

The findings highlight an important aspect of diet planning, which is that you don't necessarily need to cut out your favorite foods to maintain a healthy weight, Mangieri said. "Good things come when you learn how to eat your favorite foods in a way that helps you maintain a healthy weight, versus depriving [yourself] and feeling as if you're on a diet," she said.

The meta-analysis wasn't funded by the pasta industry; however, some of the authors previously received research grants, in-kind donations of pasta for studies and travel support from the pasta maker Barilla.

Original article on Live Science.

Is the trick to cutting cravings for sugary foods as simple as getting a good night's sleep? A new small study from the United Kingdom suggests that may be the case.

It's no surprise that tossing and turning all night can cause a person to feel tired, cranky and out of sorts the next day. But missing out on the recommended minimum of 7 hours of nightly shut-eye is also linked to various health conditions, such as obesity and cardiometabolic diseases, which include diabetes, heart disease and stroke, according to the study, published today (Jan. 9) in The American Journal of Clinical Nutrition.

Earlier research has shown that more than one-third of U.S. adults get 6 hours or less of sleep each night — less than the recommended 7 to 9 hours, according to the study. With that in mind, the researchers chose to examine whether a sleep consultation could help adults get more shut-eye and how doing so might affect their daily nutrient intake. [The Science of Hunger: How to Control It and Fight Cravings]

In the study, the researchers recruited 21 individuals to participate in a 45-minute sleep consultation designed to extend their sleep time by up to 1.5 hours per night. Another group of 21 participants were also recruited but did not receive intervention in their sleep patterns, therefore serving as the control group, according to the study.

All of the participants were asked to record their sleep and dietary patterns for seven days. During this time, the participants also wore motion sensors on their wrists that measured the exact amount of sleep they got each night, as well as the amount of time they spent in bed before they actually fell asleep.

The results showed that the participants who increased the amount of sleep they got each night reduced their added sugar intake by as much as 10 grams the next day compared with the amount of sugar they consumed at the beginning of the study. These participants also had a lower daily carbohydrate intake than the group that did not extend their sleep patterns, the study found.

"The fact that extending sleep led to a reduction in intake of [added] sugars, by which we mean the sugars that are added to foods by manufacturers or in cooking at home, as well as sugars in honey, syrups and fruit juice, suggests that a simple change in lifestyle may really help people to consume healthier diets," senior study author Wendy Hall, a senior lecturer in the Department of Diabetes and Nutritional Sciences at King's College London, said in the statement.

The group that got more sleep received a list with suggestions for how to help them get a better night's sleep — such as avoiding caffeine before bedtime, establishing a relaxing routine and not going to bed too full or hungry — as well as a recommended bedtime suited to their lifestyle.

"Sleep duration and quality is an area of increasing public health concern and has been linked as a risk factor for various conditions," lead researcher Haya Al Khatib, a professor from in the Department of Nutritional sciences at King's College London, said in the statement. "We have shown that sleep habits can be changed with relative ease in healthy adults using a personalized approach."

Overall, the results of the study showed that 86 percent of the participants who received sleep advice increased their total time spent in bed, and 50 percent of the participants extended their sleep duration by roughly 52 to 90 minutes each night, compared with the control group. What's more, three participants in the sleep-extension group achieved a weekly average within the recommended 7 to 9 hours, the researchers said.

However, the researchers noted one caveat to their findings: The data suggested that the extended amount of sleep may have been of lesser quality than the sleep of the participants in the control group. This is likely because any new routine requires an adjustment period, the researchers said.

"Our results also suggest that increasing time in bed for an hour or so longer may lead to healthier food choices," Al Khatib said in the statement. "This further strengthens the link between short sleep and poorer-quality diets that has already been observed by previous studies. We hope to investigate this finding further with longer-term studies examining nutrient intake and continued adherence to sleep-extension behaviors in more detail, especially in populations at risk of obesity or cardiovascular disease."

Originally published on Live Science.

Named after the Greek word barys for "heavy," barium is a relatively dense and reactive alkaline earth metal. It is only found naturally when combined with other elements, and compounds containing barium have a wide range of uses; they are found in rat poison, weighting agents in oil drilling fluids, and the white fluid used to visualize intestines in an x-ray diagnostic test called a barium enema.

Just the facts

• Atomic number (number of protons in the nucleus): 56
• Atomic symbol (on the periodic table of elements): Ba
• Atomic weight (average mass of the atom): 137.327
• Density: 2.09 ounces per cubic inch (3.62 grams per cubic cm)
• Phase at room temperature: solid
• Melting point: 1,341 degrees Fahrenheit (727 degrees Celsius)
• Boiling point: 3,447 F (1,897 C)
• Number of natural isotopes (atoms of the same element with a different number of neutrons): 7
• Most common isotope: Ba-138

Discovery of barium

Vincenzo Casciarolo, a 17th-century Italian alchemist, first noticed barium in the form of unusual pebbles that glowed for years after exposure to heat, according to the Royal Society of Chemistry. He named these pebbles "Bologna stones" after his hometown, but they were later determined to be barium sulfate (BaSO₄). In the late 18th century, barium oxide (BaO) and barium carbonate (BaCO₃) were discovered by German chemist Carl Scheele and English chemist William Withering, respectively. 

Pure barium metal was not isolated and identified until 1808 at the Royal Institution in London. The prominent chemist and inventor Sir Humphry Davy used electrolysis to separate the barium from molten barium salts such as barium hydroxide (Ba(OH)₂). During electrolysis, an electric current is run through the ionic substance in order to separate ions from each other. Because the barium salts were molten, the barium ions easily moved to the container with the negative electrode, and the other negative ions easily moved in the opposite direction to the container with the positive electrode.

Sources of barium

Barium is found naturally only in combination with other elements because of its high level of reactivity. Barium is most commonly found combined with sulfate and carbonate, but can also form compounds with hydroxide, chloride, nitrate, chlorate, and other negative ions. About 0.05 percent of Earth's crust is barium, making it the 17th most abundant element in the crust, according to Robert E. Krebs in his book, "The History and Use of Our Earth’s Chemical Elements: A Reference Guide" (Greenwood Publishing Group, 2006). Mining reserves in the United Kingdom, Italy, Czech Republic, United States and Germany contain over 400 million tons of barium, according to John Emsley in his book, "Nature’s Building Blocks: An A-Z Guide to the Elements" (Oxford University Press, 1999).

In order to obtain pure elemental barium, it must be separated from other elements present in naturally occurring barium compounds. Barium can be extracted from barium chloride through electrolysis. Barium can also be obtained by reducing barium oxide using aluminum or silicon in a high-temperature, low-pressure vacuum.

Properties of barium

Pure barium is a soft, silvery white metal. Classified as an alkaline earth metal, it is located in group, or column, 2 on the periodic table, along with beryllium, magnesium, calcium, strontium and radium. Each of their atoms contains two valence (outermost) electrons. Barium is in period, or row, 5, so it holds its valence electrons in its fifth shell and can lose the electrons, or become oxidized, very easily. This accounts for barium's high level of reactivity especially with electronegative elements like oxygen.

Commercial uses of barium

Elemental barium does not have many practical uses, again due to its high level of reactivity. However, its strong attraction to oxygen makes it useful as a "getter" to remove the last traces of air in vacuum tubes. Pure barium can also be combined with other metals to form alloys that are used to make machine elements such as bearings or spark plugs in internal combustion engines. Because barium has a loose hold on its electrons, its alloys emit electrons easily when heated and improve the efficiency of the spark plugs, according to Krebs.

Compounds containing barium have a variety of commercial uses. Barium sulfate, or barite, is used in lithopone (a brightening pigment in printer paper and paint), oil well drilling fluids, glassmaking and creating rubber. Barium carbonate is used as a rat poison, and barium nitrate and barium chlorate produce green colors in fireworks.

Barium in your body

The average adult contains about 22 mg of barium because it is present in foods such as carrots, onions, lettuce, beans, and cereal grains. Barium levels in your teeth can actually help scientists determine when babies transition from breast-feeding to eating solid foods. These low levels of barium serve no biological role and are not harmful. 

However, large quantities of soluble barium salts can be toxic and even deadly, according to John Emsley in his book "The Elements of Murder: A History of Poison" (Oxford University Press, 2005). Barium can cause vomiting, colic, diarrhea, tremors and paralysis. There have been a handful of murders with barium compounds, including a 1994 murder of a man in Mansfield, Texas, by his 16-year-old daughter, Marie Robards, who stole barium acetate from her high school chemistry laboratory. Several patients were also accidentally killed by barium when soluble barium carbonate rather than insoluble barium sulfate was mistakenly used during a gastroenterological (GI) diagnostic test called a barium enema. 

Doctors perform barium enemas in order to visualize and diagnose abnormalities of the large intestine and rectum, according to Johns Hopkins Medicine. During the procedure, barium sulfate is instilled via the rectum to coat the inner walls of the large intestine. Air is typically administered next to make sure the barium coating fills all surface abnormalities. Then, X-raysare used to produce an image of the lower GI tract. Barium sulfate absorbs X-rays and appears white on the X-ray film, in contrast to the air and surrounding tissue that appear black. Analysis of the X-ray image from the barium enema enables physicians to diagnose disorders such as ulcerative colitis, Crohn's disease, polyps, cancer, and irritable bowel syndrome.

Additional resources 

• Here is more info on barium from the Los Alamos National Laboratory.
• Here is what the Jefferson Lab says about barium.
• The Royal Society of Chemistry also weighs in about barium. 

Washing down your bacon cheeseburger with a big, cold soda may trigger the body to store more fat than it would if you drank something without sugar, a new small study finds.

When the people in the study added a sugary drink to a protein-rich meal, their bodies’ fat-burning ability decreased by 8 percent on average, the researchers found. In addition, the sugary drinks also appeared to increase their food cravings after the meal.

"We were surprised by the impact that the sugar-sweetened drinks had on metabolism when they were paired with higher-protein meals," lead study author Shanon Casperson, a research biologist at the U.S.  Department of Agriculture's Agricultural Research Service, said in a statement. [11 Ways Processed Food is Different from Real Food]

"This combination also increased study subjects' desire to eat savory and salty foods for four hours after eating," Casperson added.

Indeed, earlier research has shown that people who increase their protein intake experience changes  both in how food is processed by their body and in how much they eat, according to the study, published July 20 in the journal BMC Nutrition. For example, research suggests that a higher protein intake is linked to an increase in the body's fat-burning abilities.

The new findings suggest that adding sugary drinks to a high-protein intake may have the opposite effect: The sugar-rich beverages may slow the body's burning of fat, according to the study.

Isolation chambers

For the study, the researchers recruited 27 healthy young adults, gave them special meals and then observed them in special isolated rooms called "room calorimeters."  The rooms had a bed, a toilet, a sink and some other furniture, and equipment to measure the levels of oxygen and carbon dioxide along with temperature and air pressure. These measurements allowed the researchers to calculate how the foods the participants ate affected their metabolism, including how many calories they burned and how they broke down fat, protein and carbohydrates.

The participants spent two 24-hour periods in the rooms. Each period started at 4 p.m., and each participant had dinner at 5 p.m. in the chamber. The participants then fasted until breakfast the next morning. [8 Reasons Our Waistlines Are Expanding]

Then, the experiment really began. During one stay in the room, the participants were served breakfast and lunch meals that each contained 15 percent protein. Each meal was served with a sweet drink that contained either sugar or an artificial sweetener. If the drink with sugar was served at breakfast, the participant received the artificially sweetened drink at lunch, and vice versa. This allowed the researchers to see if there was any difference between how the meal was metabolized when it was combined with sugar, versus without sugar.

After both breakfast and lunch, the participants were observed for 4 hours. During this time, the researchers could see how the body responded to the meal with either a sugary drink or an artificially sweetened drink.

During their other stay in the room, the participants were served breakfast and lunch meals that each contained 30 percent protein. 

The researchers found that when a sugar-sweetened beverage was served with a meal, the participants' fat-burning ability was 8 percent lower than it was when the meal was served with an artificially sweetened drink. In addition, although the sugary drinks added more calories to the meals, they didn't cause the participants to feel fuller after eating.

In other words, sugary drinks seem to decrease the body's fat burning and don't contribute to feeling fuller. The findings "provide further insight into the potential role of sugar-sweetened drinks — the largest single source of sugar in the American diet — in weight gain and obesity," Casperson said.

More research including more people over a longer period is needed to confirm the findings.

Originally published on Live Science.

CHICAGO — The nutrients in the food you eat can worsen or lessen symptoms of inflammatory bowel disease, a new study from Canada finds.

Inflammatory bowel disease involves having chronic inflammation in the digestive tract. The two main types of the condition are ulcerative colitis and Crohn's disease. An estimated 3 million adults in the U.S. have inflammatory bowel disease (IBD), according to a recent government survey, conducted by the Centers for Disease Control and Prevention.

Although the exact causes of IBD are not well-understood, "it makes sense that what you eat would have an effect on what's happening in your gut," said lead study author Dr. Christopher Sheasgreen, a fellow in inflammatory bowel diseases at the University of Toronto and Mount Sinai Hospital Toronto. Sheasgreen presented his findings here on May 6 at Digestive Disease Week, a scientific meeting focused on digestive diseases. [5 Ways Gut Bacteria Affect Your Health]

However, there's very little data available on how foods affect the gut, so Sheasgreen decided to investigate, he said.

In the new study, 69 IBD patients were asked to fill out food diaries three to four days before a scheduled colonoscopy. The patients had either Crohn's disease or ulcerative colitis, though some patients had not yet had their specific type of IBD determined.

Using specialized software, the researchers analyzed the food diaries for the amounts of various nutrients present in each person's diet. Then, the researchers looked at two outcomes: whether the patients were experiencing any symptoms (such as diarrhea or abdominal pain) and what was going on in their guts.

More than 60 percent of the patients had no symptoms of IBD, the researchers found.

But the colonoscopies provided the researchers with information about what was happening on the inside of the patients' guts. The colon of someone during a flare-up of IBD looks different than the colon of someone who is not experiencing a flare-up, Sheasgreen told Live Science. Nearly 40 percent of the patients had no signs of flare-ups during their colonoscopies, the study said.

When the researchers compared these outcomes to the food diaries, the most interesting finding was that eating a greater amount of carbohydrates was associated with more symptoms of IBD, but no signs of an IBD flare-up in the gut, Sheasgreen said.

This finding seems "paradoxical," Sheasgreen said. However, one possible explanation is that the patient's symptoms could be linked specifically to types of carbohydrates called fermentable carbohydrates, he said. (The study didn't differentiate among types of carbs, he added.) These carbohydrates do cause abdominal symptoms, but they're not known to cause damage to the colon, he said. [The Poop on Pooping: 5 Misconceptions Explained]

A wide variety of foods contain these carbohydrates; that includes onions, apples, beans and certain artificial sweeteners.

The study showed only an association; it did not prove that carbohydrates cause these effects in people with IBD, Sheasgreen noted. More studies are needed to fully tease out the effects that different nutrients have on IBD, he said.

But the results can offer "a little bit of validation to patients" who say that the foods they eat affect their disease, he said.

Sheasgreen also noted that it's common for patients with IBD to have symptoms even when the individuals are not having a flare-up, just as people who don't have IBD also experience stomach pain and diarrhea from time to time. 

The findings have not yet been published in a peer-reviewed journal.

Originally published on Live Science.

A new book challenges the long-standing belief that when it comes to weight loss, calories are what count.

In Dr. David Ludwig's book "Always Hungry?" (Grand Central Life & Style, 2016), he argues that the type of foods you eat — not just the number of calories in those foods — ultimately affects the number of calories you burn. 

"Our mantra is 'Forget calories. Focus on the quality of what you eat, and let your body do the rest,'" said Ludwig, the director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital. [The Great Calorie Debate]

Indeed, the shift toward quality and away from quantity is gaining ground among some experts who have studied how diet affects weight.

When it comes to weight loss, the question isn't really about whether low-carbohydrate diets are better than high-carbohydrate diets, or low-fat diets versus higher-fat ones, but rather it's overall low quality versus high quality, said Dr. Dariush Mozaffarian, the dean of the Friedman School of Nutrition Science and Policy at Tufts University.

However, the majority of scientists are still focused on the total number calories, Mozaffarian told Live Science.

Dr. Louis Aronne, the director of the Comprehensive Weight Control Center at Weill-Cornell Medical College in New York and the author of the book "The Change Your Biology Diet" (Houghton Mifflin Harcourt, 2016), agreed with Mozaffarian.

The advice in the new book "is a huge change" from past advice for weight loss, Aronne said.

Which came first: Overeating or weight gain?

In "Always Hungry?", Ludwig argues that the problem is not that overeating makes you gain weight, but rather that the process of gaining weight actually leads you to overeat.

To explain, Ludwig points to what happens when you eat highly processed carbohydrates. First, there is a spike in the hormone insulin. That insulin causes fat cells to suck up calories and hold onto them, Ludwig told Live Science. ("This is endocrinology 101," he added.) In an optimal metabolic environment, those calories would be released from the fat cells the next time the body needed energy, but in an overweight person, the fat cells are stuck in storage mode, and they don't ever release those calories, he said. So, when the body needs energy, the brain signals hunger, he said, and thus, the person overeats. 

To change insulin levels, you need to reduce the amount of processed carbohydrates in your diet, and replace those carbs with fat and an adequate amount of protein, Ludwig said. When you do this, insulin levels drop and the fat cells are able to release their excess calories back into the body, he said. When this happens, hunger decreases, metabolism starts to speed up, and weight loss can occur without your body fighting back, he said.

Insulin and beyond

Not all experts agree that insulin is the main driving factor for weight gain and weight retention.

Insulin is part of it, but there are many factors at play, Mozaffarian said. For example, the foods we eat can affect our gut bacteria, the liver and the brain, he said.

Indeed, the effects of certain foods and body weight on the brain are a growing area of interest for researchers.  

For example, there's evidence that in the process of gaining weight, damage occurs to critical nerves in the brain region called the hypothalamus that regulate metabolism, Aronne told Live Science.

And other hormones are also at play.

Leptin, the hormone that signals satiety (the feeling of fullness), plays an important role in weight control, said Dr. Amy Rothberg, an assistant professor of internal medicine in the division of metabolism, endocrinology and diabetes at the University of Michigan Health System.

People with higher amounts of body fat have higher amounts of leptin, Rothberg told Live Science. These people can develop leptin resistance, meaning they don't pick up on the signal that they've gotten enough calories, she said.

(Ludwig noted that he thinks leptin is critical as well, but said it comes into play only after the insulin spikes have taken their toll.)

Calories versus carbohydrates

Rothberg said she thinks it all still comes down to calories. But the evidence does show that certain foods may be better at helping weight loss than others, she added. 

Indeed, while not all experts agree that calories don't count, there is agreement that different types of calories may have different effects on the body. [Diet and Weight Loss: The Best Ways to Eat]

"I'm persuaded by the evidence that when it comes to body weight, calories are what matters," said Marion Nestle, a professor of nutrition and food studies at New York University. "If you want to lose weight, eating less works every time."

"With that said, overall health depends on where the calories come from and some foods — the ones with sugar for example — encourage people to eat more," Nestle told Live Science.

And in the end, Ludwig said, he doesn't dismiss calories altogether. In the short term, a person can restrict their calories and lose weight, Ludwig told Live Science. The problem is that over the long term, the body starts to fight back, in part through feelings of hunger and slowing metabolism, he said.

It's not that the math behind consuming, storing and burning calories is incorrect, it's that this is not how body weight is ultimately controlled, he said. The premise of the book is that by correcting these underlying mechanisms, one can "reset" the body's weight set point (in other words, the weight that your body always seems to hover around, over time).

The experts all also agreed that weight maintenance can be difficult for many, if not most, people. 

The body is hard-wired to defend our fat mass, Rothberg said.

When a person loses weight, there's a "robust counter-regulatory response" in the body in order to regain that weight, Rothberg told Live Science. This response includes the secretion of certain hunger-driving hormones and the slowing down of the metabolism, she said.

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

From the earliest of times, philosophers and scientists have tried to understand the relationship between animate and inanimate matter. But the origin of life remains one of the major scientific riddles to be solved.

The building blocks of life as we know it essentially consist of four groups of chemicals: proteins, nucleic acids, lipids (fats) and carbohydrates. There was much excitement about the possibility of finding amino acids (the ingredients for proteins) on comets or distant planets because some scientists believe that life on Earth, or at least its building blocks, may have originally come from outer space and been deposited by meteorites.

But there are now extensive examples of how natural processes on Earth can convert simple molecules into these building blocks. Scientists have demonstrated in the lab how to make amino acids, simple sugars, lipids and even nucleotides – the basic units of DNA – from very simple chemicals, under conditions that could have existed on early earth. What still eludes them is the point in the process when a chemical stew becomes an organism. How did the first lifeforms become alive?

Although there is some debate about the definition of life, it is generally recognised that all life requires the formation of a sustainable cell, and cells must be capable of reproduction. In human cells, this is done using strands of the chemical DNA. When cells divide, they use the DNA as a blueprint for how to make the new cells.

But cell division doesn’t always produce an exact copy of the DNA. Usually this copying mistake, or mutation, is a disadvantage and the cell can be discarded. But sometimes the mutation confers a benefit or advantage to the cell (or organism) in its present environment. In this case we say it is “selected”, meaning that it thrives and multiplies to the detriment of other cells.

It’s all in the chemistry

But how did the very first cells emerge? Living systems are chemically based and therefore must obey the laws of science. Life appears to be just a series of chemical reactions – and we now understand how these reactions work at the molecular level. So surely this should tell us how life came about?

The conversion of these simple biomolecules into more complex ones has been observed under a variety of elementary conditions. For example, fatty acids – a type of lipid building-block molecule – naturally clump together into membrane-like structures, called vesicles, and even undergo chemical processes that resemble cell division and replication. Making simple replicating systems under self-sustaining conditions has also been shown to occur for both simple nucleotides (fragments of DNA) and peptides (fragments of proteins).

Creating order

The real problem is in understanding how this “machinery” of chemicals came together to generate life. The watershed where lifeless chemical activity is transformed into organised biological metabolism is extremely difficult to identify and the trigger for this is a key ingredient missing from the “primordial soup”.

The assumption that early life forms must have been similar to what we see today may be preventing us from answering this question. It’s possible that there were many unsuccessful precursors that bore little resemblance to present-day life. There has been speculation that primitive starting points could even have been based around an element other than carbon (the substance at the heart of all life today). Some researchers suggest that life may have originally evolved in liquids other than water. These alternatives are fascinating, but it’s difficult to find a starting point for researching them because they are so unfamiliar.

Off balance

A key trait that sets life apart from inanimate matter is its reliance on organisation. Molecules must be arranged in a specific way and replicate according to a detailed pattern. But the natural tendency of the whole universe is towards a state of equilibrium, or balance – where everything is spread out and nothing is ordered. Maintaining an ordered structure means life is constantly off-balance and this requires energy, which organisms must extract from their surroundings.

One way that organisms do this is to cause movement of molecules or even sub-atomic particles that can then generate energy for a cell. For example, organisms living in hydrothermal vents on the sea floor get their energy from the transfer of protons through the cell membrane.

Living systems maintain their “off-balance” state by combining the ability to self-replicate with the ability to extract energy from their surroundings. To discover the origin of life, we need to understand how these properties combined to form a sustainable unit.

Some scientists are adopting a top-down approach, attempting to answer this question by removing bits of a living cell to determine the minimum structure required to sustain life. Others are approaching it from the bottom-up by combining the building blocks in a primitive container to mimic a simple cell.

While both approaches may be enlightening, the precise moment of transition from chemical to life (and vice versa) still evades us. But the lack of discovery is fascinating in itself – it confirms that creating life is difficult and requires conditions that are no longer naturally present on the Earth. A breakthrough in this area would not only tell us the requirements for life, but also the circumstances of its emergence.

Michael Page, Professor of physical organic chemistry, University of Huddersfield

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.

Following a low-fat diet may help dieters lose more body fat than following a low-carb diet, according to a new study.

Researchers found that people in the study lost 3.1 ounces (89 grams) of fat per day, on average, when they followed a low-fat diet for six days. In comparison, the same people lost 1.9 ounces (53 grams) of fat per day while following a low-carb diet for the same amount of time.

"A lot of people have very strong opinions about what matters for weight loss, and the physiological data upon which those beliefs are based are sometimes lacking," study author Kevin Hall, a metabolism researcher at the National Institute of Diabetes and Digestive and Kidney Diseases, said in a statement. "I wanted to rigorously test the theory that carbohydrate restriction is particularly effective for losing body fat, since this idea has been influencing many people's decisions about their diets."

For the study, the researchers recruited 19 obese people whose average age was 35. During the first five days of the study, the participants ate a baseline diet of 2,740 calories per day, with 50 percent of the calories coming from carbohydrates, 35 percent from fat and 15 percent from protein. Then, for six days, the people followed this diet but cut 30 percent of the total calories by reducing their intake of carbohydrates. [Dieters, Beware: 9 Myths That Can Make You Fat]

After taking a break for a few weeks, the people again followed the baseline diet for five days. Then, for the next six days, they followed a low-fat diet, cutting 30 percent of the total calories by reducing their intake of fat.

While they were following the diets, the people in the study stayed at the laboratory, and the researchers closely monitored and controlled what the people ate.

Some proponents of low-carb diets have claimed that cutting carbs reduces the production of insulin, which in turn increases the breakdown of fat, leading to greater fat loss than low-fat diets, the researchers said.

But in the new study, the researchers found that, although following a low-carb diet did reduce insulin production and increase the breakdown of fat, these changes did not translate into an increased loss of body fat, compared with the amount of fat the participants lost while following a low-fat diet.

It is too early to make specific recommendations based on the study as to which diet people should choose to lose weight, the researchers said. The diet that the people in the study followed was strictly controlled and it did not emulate normal, real-world dieting, they said.

Moreover, the researchers noted that staying on any diet over time is important for weight loss. "What [the new study] doesn't say is whether or not, for example, a low-carb diet might be easier to stick to" than a low-fat diet, Hall said.

Previous research has shown, for instance, that people may lose more weight on low-carb diets than low-fat diets over six months of dieting. "Maybe it is because it is easier to stick to, maybe you feel full, maybe you don't feel as hungry," Hall told Live Science. But more research is needed to look at these factors, he added.

The new study was published today (Aug. 13) in the journal Cell Metabolism.

Follow Agata Blaszczak-Boxe on Twitter. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Is the pendulum swinging back? In what seems contrary to mainstream dietary advice, a small new study shows that doubling the saturated fat in a person's diet does not drive up the levels of saturated fat in the blood.

Rather, the study found that it was the carbohydrates in people's diets that were linked with increased levels of a type of fatty acid linked to heart disease and type-2 diabetes. The results of the study, which followed 16 middle-aged, obese adults for 21 weeks, were published Nov. 21 in the journal PLOS ONE.

Saturated fats, largely from meat and dairy products, have been vilified for decades as a primary culprit in promoting heart disease. And most health authorities maintain this stance.

However, in recent years, scientists have seen the ill effects of completely replacing saturated fat with carbohydrates, particularly the simple carbs that are found so commonly in processed foods. A large analysis published in 2009 in the American Journal of Clinical Nutrition found that swapping saturated fats with carbs had no benefit in reducing people's risk of heart disease. But replacing those so-called bad fats with polyunsaturated fats — found in fish, olives and nuts — did.

"The unintended consequence of telling everyone to restrict fat was that people ate an even greater amount of carbohydrates," said Jeff Volek, senior author on the new study and a professor of human sciences at The Ohio State University. "This is a fact. It's not a stretch to make the connection between overconsumption of carbs and the obesity and diabetes epidemic."

The new study "challenges the conventional wisdom that has demonized saturated fat," Volek said, because it shows that saturated fats don't need to be replaced at all, neither with carbs nor polyunsaturated fats. [7 Foods You Can Overdose On]

The study, it should be noted, was funded by a grant from the Dairy Research Institute, the National Cattlemen's Beef Association, the Egg Nutrition Center, and the Robert C. and Veronica Atkins Foundation, although the researchers reported that the funders had no role in the study design or decision to publish the research.

For the analysis, researchers placed 16 participants on a tightly controlled diet of fats and carbs. The participants were on their own high-carb, low-fat diets before entering the study. For the first three weeks of the study, they doubled or tripled their saturated-fat intake, consuming 84 grams of saturated fats, and 47 grams of carbs per day. Researchers found no jump in the levels of saturated fat in the blood during this phase.

Then, every three weeks after this, the dieters decreased the fat and increased their carb intake, ending the study on a diet of 32 grams of saturated fat and 346 grams of carbs per day. The final phase modeled U.S. dietary recommendations for carbs and included whole grains.

"You can sort of think of this experiment as a dose-response study, where we exposed individuals to a range of dietary carb levels and monitored their fatty-acid levels to determine if they were accumulating saturated fatty acids and turning carbs into fat," Volek told Live Science.

The researchers found that as the amount of dietary fat was decreased, there were no changes in the levels of saturated fat in the participants' blood. But one kind of fatty acid, called palmitoleic acid, did progressively increase.

"Higher proportions of palmitoleic acid in blood or adipose tissue are consistently associated with a myriad of undesirable outcomes, such as obesity, …inflammation, metabolic syndrome, type 2 diabetes, coronary disease, heart failure, and incidence and aggressiveness of prostate cancer," the researchers wrote.

Dr. Dariush Mozaffarian, dean of the Friedman School of Nutrition Science & Policy at Tufts University, who was not involved in the research, described the work as a well-controlled interventional study confirming that dietary refined carbohydrate is the primary driver of circulating saturated fatty acids in the bloodstream.

"White bread, rice, cereals, potatoes, and sugars — not saturated fat — are the real culprits in our food supply," he Mozaffarian.

Dr. Walter Willett, the chair of the Department of Nutrition at Harvard School of Public Health, also thought this was a reasonably done study, but he added it is difficult to make conclusions about the risk of heart disease from a study so small and short.

"Basically in their study they are comparing two bad diets, and the adverse of carbohydrates is likely to be particularly serious in the obese and insulin resistant population that they studied," Willett said.

We know from many long-term studies, Willet added, that replacing saturated fats from red meat and dairy with vegetable fats high in polyunsaturated and monounsaturated fats will reduce risks of heart disease. This is characteristic of the Mediterranean diet.

Also, other studies have shown beneficial properties of dietary palmitoleic acid, and its role in health remains an open question.

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on LiveScience.

Despite the popularity of low-carb diets, more Americans still try to avoid fat than carbs, according to a new poll.

The results show that 56 percent of Americans say they actively avoid fat in their diets, compared with 29 percent who say they avoid carbohydrates, according to the poll, conducted this month by Gallup.

However, the percentage of Americans who try to avoid fat has dropped slightly in recent years, by about 8 percentage points since 2004, according to Gallup. This trend may reflect recent research that has called into question the view that fat is the main culprit in weight gain, and instead points to processed carbohydrates as the key drivers, Gallup says. Last month, Time magazine ran an article with the headline "Ending the War on Fat," which discussed this research.

Among Americans who are trying shed pounds, avoiding both fat and carbs is common. Nearly three-quarters (73 percent) of Americans who are trying to lose weight say that they avoid fats, according to the Gallup poll. A smaller portion, 44 percent, say they avoid carbs, but this is higher than the national average, Gallup says. [7 Biggest Diet Myths]

"Many dieters appear to take advice from both schools of thought [low-carb and low-fat], a reminder that dieters must customize and improvise to find the right balance for themselves," Gallup said in a statement.

Interestingly, 12 percent of Americans who are trying to lose weight say that they try to include fats in their diet.

The poll involved about 1,000 U.S. adults ages 18 and older living in all 50 states and the District of Columbia, and was conducted between July 7 and 10.

Follow Rachael Rettner @RachaelRettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

For men with prostate cancer, consuming vegetable fats — like those found in olive oils, nuts and avocados — instead of animal fats or carbohydrates may bring a longer life, according to new research.

In the study, prostate cancer patients who substituted 10 percent of their daily calories from carbohydrates with vegetable fat were 29 percent less likely to die from prostate cancer over an eight-year period. They were also 26 percent less likely to die of other causes.

And an extra serving (1 ounce) of nuts per day was linked with an 11 percent lower risk of death from any cause, the researchers said.

The study is one of the first to examine the effect of fat consumption on prostate cancer survival in men already diagnosed with the disease.

"Our findings support counseling men with prostate cancer to follow a heart-healthy diet, in which carbohydrate calories are replaced with unsaturated oils and nuts," the researchers write today (June 10) in the journal JAMA Internal Medicine.

However, the study only found an association and cannot prove a cause-and-effect link between vegetable fat consumption and survival. While the researchers took into account many factors that could influence patients' risk of death — such as medical treatments, body mass index, and smoking and exercise habits — there may be other factors that explain the link, including the timing of cancer treatments and the way the animal fat was cooked.

Future studies should explore the benefit of vegetable fat consumption for men with prostate cancer, the researchers said.

The study looked at 4,577 men diagnosed between 1986 and 2010 with prostate cancer that had not spread to other parts of the body. Participants answered questions about their diet every 4 years, and were followed for an average of 8.4 years.

During the study, a total of 1,064 men died. Thirty-one percent died from cardiovascular disease, 21 percent from prostate cancer and about 21 percent from other cancers.

In an editorial accompanying the study, Dr. Stephen Freedland, of the Duke University Medical Center in Durham, N.C., writes that obesity is the only controllable factor known to be reliably linked with death from prostate cancer.

"Thus, avoiding obesity is essential," Freedland said. The new study suggests substituting healthy fats for unhealthy foods may be one way to do this, he said.

However, further research is needed to determine whether the link is due to lower consumption of "bad" foods or increased consumption of "good" foods, Freedland said.

Follow Rachael Rettner @RachaelRettner. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.com.

An old high school friend of mine was in town for the weekend, and I was glad to be able to spend some time catching up.

I cooked a nice balanced meal for her to enjoy with me and my family. It was really a great night. But after the plates were cleared, she remarked that she didn't expect to see such a large helping of brown rice on every plate.

I wasn't surprised. I know how confused we all are about carbohydrates, and I also know why.

In the 1970s, Dr. Robert Atkins waged war on carbohydrates, advocating a high-protein, no-carb diet for optimal health and weight loss. Millions jumped on board and sent carbohydrates packing, and the carb's reputation hasn't been the same since.

But, the American Heart Association (AHA) warns that a low-carb diet may not be a healthy diet, stating on its website that "diets low in carbohydrates are likely to lack sufficient amounts of essential nutrients." If you're following a carb restricted diet, you might not be getting enough vitamins, minerals and fiber for optimal health.

That's why the AHA and the U.S. Department of Agriculture recommend including whole grains in your daily diet. But, don't go running to the cookie jar just yet. These aren't just any carbohydrates we're talking about — these are the healthy foods that are low in saturated fat, trans fat and cholesterol.

If you're concerned about gaining weight, you might still be thinking about the wrong kind of carbohydrates. Sugar is a carbohydrate, but no one is advocating adding more sugar to your diet. On the other hand, whole grains such as rice are a welcome addition.

A Tufts University study this year showed that children and adults who eat rice regularly consume significantly more iron, potassium, B vitamins (including folate), vitamin D, phosphorous, magnesium, copper and zinc. These people also consumed a lower percentage of calories from fat than the study participants who didn't eat rice regularly. It's important to note that this study was funded by the Rice Foundation, but it does support the dietary advice given by the AHA and USDA.

Brown rice and wild rice are complete, whole grain foods, but rice isn't the only whole grain you should consider. Actually, keeping to just one whole grain would be boring and unnecessary. There are many nutritious whole grains that you can add to your diet.

Here are just a few:

• Quinoa: Quinoa is the grain that isn't really a grain. It's actually a seed, but it contains a lot of the same nutrients as grains, including fiber, phosphorous, magnesium and iron.
• Old-fashioned rolled oats: These make for a quick breakfast that's packed with fiber and B vitamins.
• Rye bread: Rye is a good replacement for white bread because it's very high in fiber, and contains very little fat.

Healthy Bites appears on MyHealthNewsDaily on Wednesdays. Deborah Herlax Enos is a certified nutritionist and a health coach and weight loss expert in the Seattle area with more than 20 years of experience. Read more tips on her blog, Health in a Hurry!

The Borg had it wrong. Resistance is not futile. In fact, it can stave off colon cancer and ease inflammatory bowel disease and other digestion problems.

The resistance, in this case, comes in the form of so-called resistant starches, certain kinds of carbohydrates that resist digestion in the small intestine and enter into the large intestine, or colon, mostly in the same form they entered your mouth.

These starches — found in seed hulls, parts of corn and beans, and in room-temperature rice and pasta — can ferment in the colon to promote the growth of "good" bacteria and have many other beneficial effects.

Researchers at the University of Colorado Denver summarize these benefits in a review paper in the current issue of the journal Current Opinion in Gastroenterology. The review includes the researchers' own findings concerning resistant starch and weight control. [The Scoop on 7 Perfect Survival Foods]

Starch vs. fiber

The word "starch" often is confused with fiber. Both are complex carbohydrates, and both are important for good health. But starch, for the most part, is highly digestible; and fiber is not. Starches are found in root vegetables, tubers, winter squashes, grains and legumes. Your body starts digesting these starches from the moment you start chewing, extracting nutrients and energy.

Fiber is more like the natural packaging for fruits and vegetables, such as the skin or the rigid cellular walls of plants. The human body does not absorb nutrients or energy from them. Soluble fiber dissolves in water, making food more viscous, slowing digestion, and prolonging the feeling of fullness. Insoluble fiber absorbs water and promotes regular and firm bowel movements.

Resistant starch has properties of both soluble and insoluble fiber, said Janine Higgins, lead author on the review paper and associate professor of Pediatrics at the University of Colorado School of Medicine. There are five different forms of resistant starch, she said, and each kind reaches the colon largely unscathed to do its handiwork.

Cures what ails you

Resistant starch might sound like some kind of miracle cure-all, but independent studies have found this substance, more so than ordinary dietary fiber, can help: kill precancerous polyps in the colon; prevent diabetes by improving insulin sensitivity and regulating blood sugar; maintain healthy body weight; reduce inflammation; prevent or treat inflammatory bowel disease; and help promote the growth of beneficial bacteria in the gut.

In 2010, scientists at Virginia Polytechnic and State University reported that resistant starch might also protect against breast cancer.

So, how can a bit of indigestible starch do all this?

"Resistant starch is a very good substrate for fermentation," Higgins told LiveScience. "Instead of being digested by amylases in the upper digestive tract, it passes to the bowel, where it is fermented by bacteria into short chain fatty acids (SCFA). SCFA are acidic, so they lower bowel pH, which facilitates proliferation of good bugs and inhibits growth of pathogenic bacteria. All of this extra fermentation and availability of SCFA provides fuel or energy for the colonocytes [cells lining the colon], which are a barrier against infection."

"Therefore, the lining of the bowel thickens and becomes healthier, and more good bugs colonize and thrive," Higgins added. "In this way, resistant starch acts as a probiotic. Resistant starch also has some of the properties of insoluble fiber, so it increases stool bulk and decreases transit time, both of which are indicators of bowel health."

Also, butyrate, a type of SCFA, seems to be involved in the prevention of bowel cancer, Higgins said.

Most high-fiber, vegetable-based diets will be rich in resistant starches, but some extra care is needed to get them into your diet. For example, pasta and rice have resistant starch, but only at room temperature. So, pasta salad and sushi are better sources of resistant starch. Whole grains, peas, and beans have a form of resistant starch that maintains its structure even when hot, though.

Green banana flour is another source of resistant starch, and it is gluten free.

Christopher Wanjek is the author of a new novel, "Hey, Einstein!", a comical nature-versus-nurture tale about raising clones of Albert Einstein in less-than-ideal settings. His column, Bad Medicine, appears regularly on LiveScience.

Eating avocados regularly may improve the quality of your diet and some key heath markers, according to a new analysis.

After crunching the data from the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2008, researchers found that eating avocados was associated with an overall better-quality diet; higher levels of HDL (the "good" cholesterol); a lower risk of metabolic syndrome; and a lower body weight, body mass index (BMI) and waist circumference.

Metabolic syndrome, characterized by a cluster of symptoms, raises a person's risk for heart disease. The symptoms include blood pressure higher than 130/85 mmHg; a fasting blood glucose level of 100 mg/dL or higher; a waist circumference of 40 inches or more in men and 35 inches or more in women; HDL ("good") cholesterol levels of less than 40 mg/dL in men and less than 50 mg/dL in women; and triglyceride levels of 150 mg/dL or higher. A person with three or more of these symptoms is diagnosed with metabolic syndrome.

The Hass Avocado Board supported the study. Findings were published in the recent issue of Nutrition Journal.

For the current analysis, researchers examined the diet quality of 17,567 adults ages 19 and older who participated in the NHANES survey. Of these, 347 (2 percent) ate avocados. Their mean daily avocado intake was about half of a medium avocado, containing about 114 calories, half of which come from fat.

NHANES interviewers gathered nutrition information based on 24-hour dietary recalls. The NHANES program of studies regularly assesses the health and nutritional status of adults and children in the United States. Researchers calculated diet quality using the USDA's Healthy Eating Index, which indicates how closely diets follow the Dietary Guidelines for Americans.

The study reported that people who ate avocados had significantly higher intakes of fruits and vegetables in general, and lower intakes of added sugars. The avocado eaters also had higher intakes of total fat, monounsaturated fat, polyunsaturated fat, dietary fiber, vitamin E, magnesium, potassium and vitamin K, along with a lower intake of carbohydrates.

Avocados are rich in monounsaturated fat, which has been associated with a lower risk of heart disease. Previous research elsewhere has found an estimated 19 percent reduction in the risk of coronary disease when the intake of monounsaturated fat is increased by 5 percent, the current researchers wrote. 

Avocado eaters also fared well in the weight department. People who ate avocados weighed on average about 8 pounds less than non-avocado eaters. The avocado group also had a lower BMI, 26.7 versus 28.4, and their waists were about 2 inches narrower. Finally, these respondents had higher HDL levels: an average of 55 mg/dL compared to 52.6 mg/dL for people who didn’t eat avocados.

The study does not prove a cause and effect relationship, only an association. The researchers acknowledge that the people in the study may not have accurately recalled what they ate; what's more, the pool of avocado eaters was small.

Still, the results are intriguing. "These findings suggest a role for avocados in improving dietary quality and possibly reducing the risk of metabolic syndrome in the United States," the researchers wrote. "Further research is needed to verify this epidemiological data and study the potential association between increased intake of avocados and other dietary components."

Pass it on: Eating avocados may raise "good cholesterol" levels, lower BMI and reduce the risk of metabolic syndrome.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience. Follow MyHealthNewsDaily on Twitter @MyHealth_MHND. We're also on Facebook & Google+.

People who meticulously check the calorie counts on nutrition labels and restaurant menus are in for some bad news: the tallies may be wrong, experts say.

Recent studies show that the amount of pounding, slicing, mashing and perhaps even chewing that goes into preparing and eating food affects the number of calories people get. For some foods, a proportion of the calories in them remains "locked up" during digestion, and isn't used by the body. People also expend some of the energy from food just digesting it; and even the bacteria in people's guts steal a fraction of food's calories. None of these factors are accounted for in our current system for calculating calories, which dates back more than 100 years.

Scientists have always known that calorie counts are just estimates. And over the years, some scientists have called for changes to the system. Now, researchers are again shining a spotlight on the issue, saying an overhaul of the calorie count system is needed so consumers have a better idea of exactly how many calories they get from the food they eat.

"If we're going to put the information out there on the food label, it would be nice that it's accurate," said David Baer, a research physiologist at the U.S. Department of Agriculture's Human Nutrition Research Center in Beltsville, Md. In a study last year, Baer and colleagues showed that almonds have 20 percent fewer calories than previously estimated.  Now, the researchers are considering retesting other foods, including some types of whole grains and legumes.

For the most part, the inaccuracies are small, but some foods may have actual caloric values that differ from the estimated values by as much as 50 percent, experts say. [See 9 Snack Foods: Healthy or Not?]

Counting calories

One way to measure a food's energy, or caloric content, is by burning it in a device called a bomb calorimeter. However, this method doesn't take into account the fact that humans lose some calories through urine and feces and as heat. Over the years, researchers have tried to figure out ways to account for these losses.

In the late 1800s and early 1900s, a man named Wilbur Atwater conducted experiments in which he calculated the number of calories in various diets, and collected people's feces to determine how many calories were wasted. Based on these experiments, Atwater concluded that proteins and carbohydrates have about 4 calories per gram, fats have 9 calories per gram, and alcohol has 7 calories per gram.

These values are still used today. Their existence means food manufacturers and restaurants can use a simple formula to calculate the calories in their foods.

However, these values are rough estimates. Certain foods, such as those high in fiber, are not digested as well, meaning the calories we get from them would be lower than those calculated using the formula. In the 1970s, researchers introduced modified Atwater values that were intended for specific foods, such as fruits, vegetables and beans.

More changes needed

While these changes are a good start, some experts say we should do more.

Research by Rachel Carmody, a postdoctoral fellow at Harvard University's FAS Center for Systems Biology in Cambridge, Mass., and colleagues, shows that food processing — eating a carrot that's pureed rather than whole, for example — changes the calories we get from it. 

Food processing takes some of the work out of digestion, Carmody said, meaning that generally, a processed food will have more calories than an unprocessed food.

Calories in processed foods are likely close to the values that the Atwater system estimates.For example, if you eat a mashed potato that's been calculated by the Atwater system to contain 300 calories, you're likelygetting most of those calories, Carmody said. But if you eat a whole, unprocessed potato of the same size, you'll take in around 200 calories, she said.

The difference is biggest for starchy foods, like potatoes, and is lowest for meats, Carmody said. (The calories from unprocessed versus processed meats only differ by 5 to 10 percent, she said.)

The Atwater system also fails to account for structural differences in food that make some calories inaccessible to our bodies. For example, the almond study, which also accounted for calories lost in feces, suggested that some of the fat in whole almonds is locked away in a structure our bodies can't digest. While the Atwater system says a serving of whole almonds has about 170 calories, the almond study found it actually has about 130.

"Given that the Atwater system is treating essentially all foods the same, we aren’t getting a good perspective when it come times to make dietary choices," Carmody said.

When we digest food, we also give off energy as heat. The amount of heat we radiate depends upon the exact components of the food. For proteins, it's about 20 to 30 percent of the food's calories — so if we eat 100 calories worth of protein, we get about 80 calories from it, Carmody said. For fats, it's much less, about 0 to 3 percent, she said. (So if we eat 100 calories worth of fat, we'd get 97 of those calories.)

This month, Carmody and colleagues will give a presentation at the annual meeting of the American Association for the Advancement of Science in Boston that will discuss ways in which to improve the system for calculating calories.

Does it really matter for waistlines?

Some researchers say that, on the whole, the inaccuracies in calorie estimates don't make a big difference. "For most uses, I think they're good enough," said Malden Nesheim, professor of nutrition emeritus at Cornell University, in Ithaca, N.Y., and co-author of the book "Why Calories Count" (University of California Press, 2012).

People tend to eat a variety of foods, not just almonds or starches. So overestimating or underestimating the calories in one particular food will likely not have a huge impact on a person's daily calorie intake, Nesheim said.

And generally, the omissions in the Atwater system tend to result in overestimates, meaning they likely wouldn't interfere with weight loss.

"It would only be a problem for people who want to gain weight," said Mary Ellen Camire, a professor at the University of Maine's Department of Food Science & Human Nutrition in Orono.

But other researchers say the goal of a revision would be to give people as much accurate information as possible to help them make informed choices about food, Carmody said. Such a process could result in broad changes, such as new numbers for the total calories people need in a day.

"By getting a better understating of the effective calories in food, we'll get a better sense of human energy requirement," Carmody said.

A change to the calorie system would not be easy, Carmody said. And because of differences between individuals, it would be impossible to create a system that would work for everyone.

But researchers may be able to fill in some of the system's biggest gaps, such as the effects of food processing and heat loss, Carmody said.

"We can start to think of simple ways to improve [the system] that will be better for the average consumer," Carmody said.

Pass it on: An overhaul of the system we use to calculate calories is needed so people can better gauge how many calories they get from food.

Follow Rachael Rettner on Twitter @RachaelRettner, or MyHealthNewsDaily @MyHealth_MHND. We're also on Facebook & Google+.

Pasta has been unjustly vilified in recent years as a leading culprit in the rise of obesity around the globe. It has been attacked as a (gasp!) carbohydrate, a food type many health experts say we should avoid.

The obvious problem with this assessment is that pasta is a traditional food that predates the emergence of the obesity and diabetes pandemics. And in Italy — pasta central, where pasta is eaten on average at least once a day — the denizens benefit from one of the lowest rates of obesity in Europe, if not the world.

The truth is, pasta is and has long been a healthy carbohydrate and a central component of the Mediterranean diet, broadly considered one of the best lifestyle diets for maintaining a healthy weight.

How did pasta get such a bad rap? The primary reason is a simple misconception — that pasta is akin to bread made from wheat. In fact, pasta is made from durum, a wholly different species from bread wheat in that it contains a third fewer chromosomes. Durum is an older species and a hybrid of wild grasses; modern bread wheat is more domesticated.

The second reason why pasta gets criticized is what we tend to do to it: over-process it and top it with salty and fatty goo. This is what has turned inherently healthy pasta into something far less desirable. [10 Bad Things That Are Good for You]

Back to basics

The history of pasta is as long and tangled as poorly cooked linguine. The general consensus is that something like pasta made from semolina, the flour of durum, was eaten throughout the Mediterranean region as early as Roman times.

Pasta as an Italian staple likely developed in the 12th century. Soon after, in the Naples region, the locals developed a way to mass-produce dried pasta, which allowed for long-term storage and indeed helped to enable extended sea voyages.

Pasta has changed little over the last 800 years. In Italy, it was traditionally the food of peasants, which meant just about everyone. Before the introduction of tomatoes from the New World, pasta was served with olive oil, garlic or local vegetables.

Low on glycemic index

What makes pasta healthy is the fact that it has a low glycemic index (GI) — a modern concept of how fast glucose, a sugar from carbohydrates, is absorbed into the bloodstream. The GI runs from zero to 100, and foods with a higher index number tend to spike the blood with sugar. This taxes the organs — in particular, the pancreas — and can lead to diabetes and obesity.

Pasta is remarkably low on the glycemic index. Pasta is around 25 to 45, depending on the type. That's in the range of many fruits and (non-potato) vegetables. Most pasta is in the "low glycemic index" category for the South Beach Diet. That is, pasta is an encouraged food in the South Beach diet, not because it is low-carb, but rather because it is a good carb.

Compare this with two staples of the American diet: white bread, with a GI of about 75; and potatoes, with a GI of about 80. (Mashed potatoes come in at 90.) Did you have corn flakes from breakfast? They have a GI of 80, as do many breakfast cereals.

There are several reasons for pasta's low GI rank, according to Francesco Pantò, director of product development at the Barilla Group in Parma, Italy. Semolina flour comprises large, crystal-like yellow particles. Its naturally strong gluten content prevents starch from leaching out quickly, and this in turn leads to slower digestion, slower release of sugar into the blood, and a greater feeling of satiation, Pantò told LiveScience.

Also, the extrusion process — in which the unleavened semolina dough is pushed through a die to give pasta its shape — additionally creates "very compact structure, which makes the carb slowly available [in the body], hence determining a slow energy release," Pantò said.

Whole-grain semolina pasta, a recent trend, does not necessarily have a lower GI, Pantò said. Rather, the whole grain adds micronutrients lost in the milling process, which can be important but is outside of the discussion of weight gain. [8 Reasons Our Waistlines Are Expanding]

The good, the bad, the mushy

Researchers continue to confirm the healthful benefits of keeping pasta central to a diet. Pregnant women in the Netherlands who ate a pasta-centric Mediterranean diet gave birth to healthier and higher-weight babies compared with women who ate more meat and potatoes, as reported in February this year in the British Journal of Nutrition.

Researchers in United States found that eating salad with pasta combined to produce a feeling of fullness with fewer calories. Those results were published in February in the journal Appetite. And in the journal Critical Reviews in Food Science and Nutrition in January, researchers in India suggested that bringing more pasta to their country, supplemented with iron and other nutrients, could combat nutritional diseases and undernourishment.

Similarly, multiple recent studies reaffirm that a low-glycemic-load Mediterranean diet leads to healthier blood sugar and cholesterol profiles and lower weight.

If Italy has an obesity problem, it is with its children. The rate of child obesity there mirrors the United States, with about one-third of children overweight. Studies find the reason to be a departure of the traditional diet — with more meat and ultra-processed foods, such as fast food and prepared foods — and a lack of exercise.

When in Rome...

Pasta, Pantò said, should be cooked al dente, or slightly firm. Anything longer slightly raises the GI. Pasta becomes unhealthy when it is overly processed, such as the mushy stuff in a can, or when it is topped excessively with fatty meats and cheeses.

And pasta should be consumed, as with everything, in moderation, a concept sometimes lost on Americans. Italian portions, although daily, tend to be smaller than American portions. Thus, the Mediterranean diet does make room for those meats and cheeses.

As journalist and social critic H.L. Mencken wrote, "For every complex problem there is an answer that is clear, simple, and wrong." Avoiding all carbohydrates such as pasta just because they are carbohydrates seems to fit this notion.

Christopher Wanjek is the author of a new novel, "Hey, Einstein!", a comical nature-versus-nurture tale about raising clones of Albert Einstein in less-than-ideal settings. His column, Bad Medicine, appears regularly on LiveScience.

Cats will ignore your sugary treats, but will literally jump onto the counter at the chance to scarf down some meaty goodness. The behavior stems from a missing sweet-taste receptor on their tongues, and now researchers have found some of their carnivore cousins in the wild, including sea lions and hyenas, also lack the taste for sweetness.

Other carnivores, like bears, retain the sweetness receptor on their taste buds (causing Pooh Bear to keep getting his hand stuck in that honey pot), which might be because of their flexible diets, the researchers added.

"If you primarily eat meat, there isn't a need to detect carbohydrates [like sugars and starches], so there is no need to keep this receptor intact," study researcher Peihua Jiang, of the Monell Chemical Senses Center, a nonprofit scientific research institute in Philadelphia dedicated to the senses of taste and smell, told LiveScience.

Tasty genes

Scientists have known since 2006 that domestic cats are missing the sweetness receptor; the study, published today (March 12) in the journal Proceedings of the National Academy of Sciences, extends that research. Jiang and colleagues looked at 12 different carnivores, from all different groups of animals, and analyzed their taste-receptor genes. [The 7 (Other) Flavors Humans May Taste]

"We wanted to see if the cat is the exception or if this loss of taste is more widespread in the animal kingdom," Jiang said.

The researchers compared the taste genes of 12 meat-eating species with that of the dog, which can taste sweetness. They saw the sweet-taste receptor was nonfunctional (the gene contained mutations that would stop it from making a functional protein) in seven of the 12 carnivores they tested: the sea lion, the fur seal, the Pacific harbor seal, the Asian otter, the spotted hyena, the fossa and the banded linsang (the last two are catlike mammals).

Both the sea lion and the bottlenose dolphin lack not only the sweet-taste receptor, but also the umami (a savory flavor, long recognized in the East) taste receptors. The dolphin seems to have even lost the ability to taste bitter substances, and has very few taste buds in general.

"We found out that for the species that have a unique feeding behavior, like the feline and dolphin, which for example swallow their fish whole without chewing, they are bypassing the sense of taste," and therefore don't need these taste receptors anymore, Jiang said. "They probably don't need to have a taste to determine what they eat. They may use other means to identify their food."

Taste test

The researchers wanted to check that these defective genes led to differences in how an animal responds to different tastes. They analyzed how two carnivorous species, the Asian small-clawed otter and the spectacled bear, responded when given natural sugars and artificial sweeteners.

The Asian otter has a defective sweetness receptor, and didn't show any preference for sweet compounds, while the spectacled bear showed a strong preference for natural sugars and even some artificial sweeteners. This matches up with their taste receptor genetic data.

The researchers have previously tested several other carnivorous species, finding just one, the Asiatic lion, that didn't respond to sweetness; this lion, another feline species, also lacked the sweet-taste receptor.

You can follow LiveScience staff writer Jennifer Welsh on Twitter @microbelover. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

Eating probiotic yogurt might change the way the bacteria in your gut break down the carbs you eat, a new study suggests.

Researchers found that eating yogurt daily did not alter the species of microbes in the intestines of people, or mice transplanted with human gut microbes.

However, when the researchers looked at the activity of bacterial enzymes in the mice's guts, they discovered significant changes in some of the enzymes — particularly those involved in metabolizing carbohydrates.

Essentially, the live bacteria in the yogurt allowed the mice to break down certain classes of carbohydrates more efficiently, the study showed, and many of these changes also occurred in the study's 14 human participants.

"It's interesting that just by virtue of introducing species, you can get quite dramatic changes in the expression of genes in the gut microbes," said Susan Lynch, an associate professor of medicine at the University of California, San Francisco, who was not involved in the research.

But she says that larger studies are needed to really understand how the probiotics, or "good bacteria," affect the bacterial communities in people's intestines.

The effects of probiotics

Our guts are home to swarms of bacteria, known collectively as the microbiome. These communities help us in a variety of ways, such as harvesting energy from the food we eat, preventing the growth of harmful bacteria and producing nutrients such as vitamins K and H.

Studies have shown that probiotics, such as those found in yogurt, can help with certain intestinal issues, such as irritable bowel syndrome. Recent research suggests that ingesting probiotics may even affect our behavior and could someday treat depression.

But despite the purported health benefits of probiotics, it's unclear how exactly they affect our gut microbiomes, and influence our overall health.

In the new study, researchers recruited seven pairs of identical female twins and gave them two servings of yogurt a day for seven weeks. The yogurt had five strains of live bacteria.

"The idea of using twins is a nice one," Lynch said. "To some extent, it can standardize genetic and environmental factors that could have an affect on the results."

The researchers analyzed stool samples from the women throughout the study, and found yogurt didn't change the species or genes of the bacterial communities in the women's intestines.

In other words, the bacteria in the yogurt did not appear to colonize the participants' guts. In fact, two weeks after the women stopped eating yogurt, the researchers could not detect any live yogurt bacteria in the stool samples of the majority of the participants.

But the researchers then carried out a similar experiment with mice, and found significant changes in the way the mice metabolized carbohydrates.

A new model

Jun Sun, an assistant professor of medicine at the University of Rochester in New York, said the researcher's method of using mice with humanized microbiomes could be useful for future studies, particularly those that test the health benefits of yogurts and other fermented milk products.

The research provides a nice model to test how the introduction of different probiotics affects our gut microbial communities, Sun said. [Are Probiotics Safe?]

Lynch said studies like this "are fundamental to understanding the possible benefits of microbial supplementation approaches."

The study was published today (Oct. 26) in the journal Science Translational Medicine.

Pass it on: Some types of yogurt may alter the way you break down carbs, but more research is needed to really understand the effects of probiotics.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience. Follow MyHealthNewsDaily on Twitter @MyHealth_MHND. Find us on Facebook.

If you want to succeed in the gym, it might be best to start and end your workout in the kitchen.

Scheduling meals and snacks around your fitness schedule can make a big difference in how you feel during a workout, and how much you benefit from it afterward.

"Nutrient timing is very important," said Dr. Shawn Arent, director of the Human Performance Laboratory at Rutgers University. "You can't get the most out of working out without [paying attention to your] diet,"Arent said.

"You don't need a specific diet for regular exercise," as long as you're eating healthily, said Dr. Ben Zhou, director of the Health and Physical Fitness Testing Center at California State University Dominguez Hills. But even when eating healthy food, it's important to keep an eye on portion size, especially for those with specific fitness goals, he said.

Before your workout

It's best to eat a large meal at least a few hours before going to workout, Arent said. Ideally,such meals should combine lean protein and plenty of carbohydrates. Depending on the time of day, meals might include rice, pasta, chicken, fish, peanut butter and other healthy foods.

Arent said he also encourages people to have a smaller, high-carbohydrate snack or sports drink for energy within an hour or so of hitting the gym.

"You absolutely need to eat before you go to the gym," he told MyHealthNewsDaily.

The need to eat is especially important before extended aerobic exercise. "They need a continuous supply during long races," Zhou said.

Carbohydrates are digested and absorbed quickly compared with other nutrients, which makes them ideal to eat prior to or even during workouts, to keep energy levels high, Arent said. Proteins and fats, while necessary for nutrition, are a bad idea to eat shortly before any workout, because they take longer to digest. Exerting yourself while you have food sitting in your stomach can interfere with blood flow to the digestive tract, and can lead to stomach cramps and a heavy, lethargic feeling that impedes efficient exercise.

After your workout

Post-workout meals play as important a role as what you eat beforehand. "The more immediately after working out you eat, the better,"Arent said.

Getting food into the body helps it recover from exertion. After strenuous exercise, the carbohydrates stored in the muscles and liver may be used up, and the protein making up the muscles is partially broken down.Those nutrients need to be replaced.

The total amount of food someone should eat can vary widely based on their size, goals and exercise routine. The key is to find a balance so that you take in enough nutrients to replace energy and build muscle, but no tso much that your body converts the extra to unwanted fat, Arent said.

But this simple advice can be more difficult than it sounds. "People may not want to eat immediately because they are tired," Zhou said.

Further, it's the nutritional content, not the form of the food that matters, Arent and Zhou both said. Food in liquid form, such as a smoothie or fruit juice, is often easier to take in for people tired from exercise.

Unfortunately, these options rarely have any natural protein, which plays a vital part in increasing muscle mass. One option for getting more protein is to use protein powder supplements. While they work fine in delivering protein to the body,they shouldn't be treated as a replacement for proper meals, Arent said.

It doesn't take a lot of concentrated protein to get the benefits, and overdoing it carries the same penalties as overeating anything else, Arent said. "Too much, and you will increase weight," Zhou said, adding that the powder can also spoil the taste of the beverage.

Pass it on: Eating healthfully before and after your workout maximizes the benefits of exercise, experts say.

This story was provided by MyHealthNewsDaily, sister site to LiveScience. Follow MyHealthNewsDaily on Twitter @MyHealth_MHND

A type of low-carb, high-fat diet that's typically used to manage seizures for children with epilepsy could reverse kidney disease in Type 1 and Type 2 diabetics, a new animal study suggests.

If successful in humans, the so-called ketogenic diet could have the potential to replace dialysis, which is a procedure that artificially filters blood in place of a damaged or failed kidney, said study researcher Charles Mobbs, professor of neuroscience and geriatrics and palliative care medicine at Mount Sinai School of Medicine in New York City.

"I speculate that this may be useful to completely cure diabetic kidney failure, and I hope that it's possible," Mobbs told MyHealthNewsDaily. "If it's possible, we can potentially not require dialysis. That's a big deal."

However, a lot more research in mice is needed before any studies can be done in humans, Mobbs said, let alone determine if the diet can reverse advanced kidney disease in humans, he said.

"That's the first thing we want to establish in mice: Can we truly reset the clock? Can we completely correct the [kidney] impairments?" Mobbs said.

Other experts say the finding is promising for Type 1 and Type 2 diabetics with earlier-stage kidney disease, but more research must be done to provide evidence that the diet can make an impact on end-stage kidney disease, or kidney failure.

Type 1 diabetes is a chronic disease that occurs when the pancreas cannot produce enough insulin (needed to move blood sugar into cells for energy) to control blood sugar levels, according to the National Institutes of Health. Type 2 diabetes occurs when the body becomes resistant to insulin, leading to high blood sugar levels. Overweight and obesity, a sedentary lifestyle and poor diet are risk factors for Type 2 diabetes, according to the NIH.

The study was published today (April 20) in the journal PLoS ONE.

Reversing kidney disease

Mobbs and his colleagues induced kidney disease in mice that were genetically engineered to have Type 1 or Type 2 diabetes. They measured proteins in the mice's urine until levels were 10 times higher than normal, which is a telltale sign of kidney disease.

Then, half the mice were put on a ketogenic diet (87 percent of calories from fat, with a moderate amount of calories from protein and few calories from carbohydrates), and the other half were put on a standard high-carbohydrate diet, according to the study.

After eight weeks, researchers found that kidney disease was reversed, and damage to the organ had been repaired, in the mice that were on the ketogenic diet, the study said, though there was less damage repair in the mice with Type 2 diabetes than the mice with Type 1 diabetes.

Researchers also found that expression of genes that indicate kidney failure were turned off in the mice fed the ketogenic diet, according to the study.

When a person consumes a ketogenic diet, blood levels of ketones are elevated (a state called ketosis). The body's cells are able to get energy from ketones, which are molecules that are produced when fat levels in the blood are high and blood glucose levels are low, Mobbs said. Essentially the body burns fat rather than carbs (called glucose metabolism) for fuel.

"The key to the whole study is that ketones block glucose metabolism," Mobbs said. "Pretty much everybody agrees that diabetic complications are caused by too much glucose metabolism in the cell, so it was kind of an obvious hypothesis that if you can increase ketones long enough, that that would block glucose metabolism and allow the cells to recover from their damage."

However, this is simply a hypothesis — more research is needed to determine the exact mechanism by which ketones work to reverse kidney damage in mice, he said.

"There are a lot of things we don't know yet about how [the ketones are] working," Mobbs said.

It's also possible that the diet works by promoting stem cells to replace damaged cells in the kidneys, he said.

If the findings can be replicated in humans, Mobbs said the diet shouldn't be consumed for long periods of time. Rather, one month of the diet could be sufficient in reversing the kidney damage, he said.

Implications of the findings

Past research has shown that a low-protein diet has a small effect in slowing kidney-function decline in humans. However, that study, published in 1994 in the New England Journal of Medicine, didn't show that a low-protein diet made a difference in people with advanced kidney disease.          

However, what may make this ketogenic diet work better than a purely low-protein diet is the fact that the diet induces ketosis (high ketone levels in the blood), said Dr. Leslie Spry, spokesman for the National Kidney Foundation and volunteer professor at the University of Nebraska Medical Center, who was not involved with the study.

"The new part of this would be the ability to achieve and maintain ketosis in an individual with caloric restriction," Spry told MyHealthNewsDaily.

However, Spry said he would be surprised if the diet worked in someone with advanced diabetic kidney disease, because of the great amount of damage to the kidneys that is associated with that stage of disease.

"I would very much doubt that late kidney disease would be reversible, and I would be dubious about that," Spry said. Therefore, researchers must be able to prove that ketosis can actually reverse the effects of kidney disease in humans before the diet can be considered a replacement for dialysis, he said.  

Pass it on: Though more research is needed before it can be proven in humans, a ketogenic diet reverses kidney disease in mice with Type 1 and 2 diabetes.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @AmandaLChan.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience.

It's common to take a nap after the huge Thanksgiving feast and blame your drowsiness on the natural sleeping potion chemical tryptophan, found in turkey meat. But does turkey make you sleepy?

Turns out, it's only marginally true. What makes you sleepy after Thanksgiving dinner is any combination of booze, bad conversation and a carbohydrate-heavy meal, but not just the turkey itself.

Tryptophan is an essential amino acid that the body uses to build certain proteins and it can, although somewhat indirectly, induce sleep. The body uses tryptophan in a multi-step process to make serotonin, a neurotransmitter in the brain that helps regulate sleep.

Related: What if you ate only one type of food?

It's true that turkey contains tryptophan, but it's not as loaded with the stuff as you might think: all meat contains comparable levels of the amino acid, so it shouldn't make you any sleepier than, say, bacon. In fact, cheddar cheese, gram for gram, has more. Cheddar isn't the most exciting cheese in the fridge, but no one connects it with sleep. Turkey gets singled out for no other reason than being eaten during the biggest meal of the year.

In essence, any big meal with any food containing tryptophan can cause sleepiness. The real culprits are all those carbohydrates from potatoes, stuffing, vegetables, bread and pie. The massive intake of carb-heavy calories causes the release of insulin, which triggers muscles to suck up most of the amino acids from the blood except for tryptophan.

With all other amino acids swept out of the bloodstream, tryptophan has no trouble making its way to the brain and influencing the production of serotonin, the real sleep-inducer. Whether its from turkey, ham or any meat or cheese, a cocktail of tryptophan and carbohydrates are the real reason behind the post-dinner zzzzzzzz's.

Chris Voigt loves his job. And, it seems, he loves potatoes, too. As executive director of the Washington State Potato Commission, Voigt has pledged to eat nothing but potatoes for two months.

No toppings. No sides. Just the wholesome goodness of 20 potatoes a day to meet his caloric needs, from Oct. 1 to Nov. 29.

"I want to show the world that the potato is so healthy that you could live off them alone for an extended period of time without any negative impact to your health," Voigt explained on his website.

You don't get that kind of commitment from the scallion commissioner, that no-good lackey. But to paraphrase the announcer before any Evel Knievel stunt, "Kids, don't try this at home."

Potatoes or nuts?

Much research has been conducted on potatoes, and the conclusion drawn by every medical doctor and nutritionist on the planet is that you have to be nuts to think you can live off of potatoes.

To Voigt's credit, his lighthearted stunt will educate the public about many healthy aspects of the potato: a decent and inexpensive source of vitamin C, vitamin B₆, potassium, magnesium and, with the skin left on, dietary fiber.

Also, low-carb advocates are harsher on the potato than science allows them to be. Some potato varieties, prepared correctly, can be as healthy as the much-lauded whole grains. [7 Diet Tricks That Really Work ]

Voigt didn't enter this diet blindly. He told LiveScience he first consulted with a doctor and dietician to confirm he could go 60 days on just potatoes. You need healthy kidneys to process the excess potassium delivered by 20 potatoes a day. You also need a store of nutrients potatoes lack, such as vitamin A for proper vision, or else exit this diet blindly.

Potato vs. the world

The potato's charm is its mediocrity: It is a decent famine food, because it has modest amounts of many nutrients, as opposed to the so-called healthy orange, which just delivers vitamin C and some fiber. The United Nations has promoted the potato as a means to eliminate world hunger.

The problem is that potatoes have a high glycemic index, a measure of how quickly carbohydrates are absorbed into the bloodstream. Foods with a higher glycemic index — most notoriously, processed foods — are associated with weight gain, insulin resistance and diabetes.

Potatoes get worse with the typical preparation: mashed and served with butter or gravy, or fried and salted.

"Potatoes can be an excellent part of a healthy diet, but are not a healthy single source diet," said Barry Swanson, regents professor and interim director of the School of Food Science at Washington State University and University of Idaho, a guy who traverses the two states that produce about half of North America's potatoes. "The glucose release in the body is pretty large for most potato products since the starch is readily digestible."

This means the potato initially satisfies energy needs but, if that's your primary food source, leaves you hungry and tired a few hours later, Swanson said. Like all starches, the potato is most healthful when eaten with other vegetables.

A baked Russet has a glycemic index of 76. Most starches have a lower glycemic index, such as white rice (64), brown rice (55), lentils and beans (under 30) and barley (25), according to the Linus Pauling Institute at Oregon State University. Vinegar and cold storage lowers the glycemic index. A cold, boiled red potato has a glycemic index of 55.

For the record, Voigt told LiveScience his blood sugar level is in the mid-90s, slightly high but within normal range and actually lower than his pre-diet measurement.

Man doth not live by bread only

Can humans survive on any single food? A whale or other marine mammal might do the trick. Some Inuit have survived long periods entirely on meat, attaining vitamin C in muktuk, the skin and blubber of whales.

Surprisingly, potatoes offer a complete protein if you eat enough, over 10 per day. But you would ultimately encounter deficiencies in vitamins A, B₁₂ and E, and calcium and selenium if you keep to just potatoes. Potatoes are slightly toxic, too. The poison is in the stem and leaves, but trace amounts can be in greenish spots on the potato itself and can cause serious illness if you eat enough.

In eating any single vegetable, you are sacrificing nutrients. Soybeans, chickpeas, lentils, or carrots also provide a good range of nutrients. Subjective, yes. I welcome your suggestions.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears regularly on LiveScience.

Once upon a time, in the dark ages of the 1960s and '70s, a diabetes diet meant avoiding sugar. Refrigerators of diabetics were filled with Fresca; sugar bowls were filled with Sweet'N Low; and, for the most part, plates were still filled with meat and potatoes.

That diet didn't work so well, and self-administered insulin shots were often needed to keep blood-sugar levels safe.

The thought of a life devoid of sugar, let alone refreshment coming in the form of Fresca, might send shivers down your spine.  Fortunately, our knowledge of how to manage diabetes has grown considerably. The diet that is best for diabetics is in fact the same healthy diet rich in vegetables and whole grains recommended for everyone. The catch is that diabetics have to pay more attention to it.

Unfortunately, the myth of diabetes as the "just-don't-eat-sugar" disease lingers, and this does many a diabetic more harm than good.

Diabetes pandemic

Diabetes is largely a diet-related disease. Lifestyle changes — improved diet and regular exercise — result in a 93-percent reduction in the risk of developing diabetes, according to a massive European study published in August 2009 in Archives of Internal Medicine.

Not surprisingly, adult-onset type 2 diabetes, the most common type today, in which cells cannot use insulin properly, was a rare disease as little as 60 year ago. By 1980 about 5 million Americans had diabetes. Today over 24 million Americans, or 8 percent of the population, are diabetic, and nearly 60 million are pre-diabetic, according to the Centers for Disease Control and Prevention. Rates have paralleled the expansion of waistlines.

Diet can be your best defense in managing or warding off diabetes. The Diabetes Prevention Program, funded by the National Institutes of Health, found way back in 2002 that improved diet and exercise was better than medicine, in this case, metformin, at preventing pre-diabetics from becoming diabetics. Numerous studies have supported this.

Most recently, Italian researchers have found that diabetics who ate a Mediterranean diet rich in nuts, healthy oils, vegetables and whole grains were less likely to need medication to control their diabetes and reduced their risk of heart disease, too. This was published in September in Annals of Internal Medicine.

The real diabetes diet

Depending on the specifics of diseases, a person with diabetes or pre-diabetes would likely benefit from eating small meals, usually a modest breakfast, lunch and dinner with two or three snacks in between. The goal is regularity to keep blood sugar, or glucose, levels low and constant.

Cells use glucose, a simple sugar, for fuel. The pancreas secretes insulin to ferry that glucose into cells. Often in type 2 diabetes, muscle, liver and other cells don't absorb glucose in the presence of insulin. So the pancreas, sensing all this glucose, generates even more insulin to get the glucose into cells. A nasty imbalance ensues.

A big meal might flood the bloodstream with glucose, so smaller meals are better. Table sugar can indeed spike the blood with glucose, but so too can other simple carbohydrates such as white bread. A diabetic or pre-diabetic should eat more of the kinds of carbohydrates that don't breakdown quickly into glucose. These are known as foods with a low glycemic index, and they include most vegetables, whole grains, and low-carb foods like meat, eggs and fish.

Foods with a high glycemic index — the same stuff dominating the U.S. diet in recent years — include most processed foods, breakfast cereals, doughy white bread, baked potatoes and anything high in sugar.

Why not just go on a low-carb diet? Low-carb diets often are synonymous with high-fat diet. Aside from keeping a steady glucose level, diabetics need to maintain healthy blood pressure and cholesterol levels. This is because chronic elevated glucose levels damage blood vessels, placing a diabetic or pre-diabetic at higher risk for heart disease, peripheral vascular disease (leading to loss of feet and legs), stroke and blindness from weak blood vessels in the eye.

Diabetics need to plan out a diet dominated by foods with a low glycemic index. They can treat themselves to sugar by substituting this for any other food high glycemic index, depending on their allowance based on glucose levels.

It's not easy to stay on a healthy diet. I can't sugarcoat it, so to speak. You need to get together with a doctor and dietician. But unlike other diets you've been on, this one could be a matter of life or death.

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Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears each Tuesday on LiveScience.

Health met physics in last week's New England Journal of Medicine with a study revealing that the type of diet doesn't matter so much for weight loss — be it low-fat, low-carb, 70-percent yak meat or whatever — as long as one simple requirement is met: Consume fewer calories than you burn.

The discovery harkens back to the Age of Enlightenment and the law of conservation of energy, a concept lost in the fad-diet world for the last 200 years.

That said, not all diets are created equal. This latest health study, led by Frank Sacks of Harvard School of Public Health, does not exonerate any particular diet, as some news reports have implied. The reason is that diets should not be simply about losing weight.

Looking good in spandex is one thing; having healthy organs and a cardiovascular system is other. Fad diets tend to fail you with the latter.

Trinity of macronutrients

Many diets concentrate on what are known as macronutrients: protein, fat and carbohydrates. These contribute to nearly all of your daily calories, with the rest filled in by micronutrients — vitamins and minerals and other nutrients — plus dietary fiber, which often is lumped in with carbohydrates.

The Harvard-led study was a relatively large and methodologically sound clinical trial that followed about 800 overweight adults for two years. This group was placed on one of four kinds of diets, ranging from moderately low-carb and high-fat to high-carb and low-fat.

Regardless of the macronutrient ratios, the patients lost the same amount of weight, about 13 pounds after one year but a total of about 8 pounds at the end of two years.

The study's strengths are the size, duration and the systematic approach to uncover the reason for the mixed reports from other health studies concerning the efficacy of this diet versus that diet. There's never a final word when it comes to health studies, but this Harvard study is pretty close.

The study's weakness was the failure to keep patients faithful to their particular diet. But then again, this could be another strength, because this is the real world and emphasizes the problem with fad diets.

Atkins replies

Ever defensive, Atkins Nutritionals issued a rebuttal to the Harvard study a day after its publication, claiming that the low-carb ratios used in that study doesn't come close to the levels Atkins recommends. This claim is true, of course, in all its classic Atkins irony.

The Harvard study dipped as low as 35 percent for calories derived from carbohydrates (with a corresponding fat level of 40 percent). The first phases of the Atkins diet recommends that only 10 to 25 percent of calories are derived from carbohydrates. The problem is that many health experts view these levels to be unhealthy.

The World Health Organization recommends a range of 50 to 70 percent of calories come from carbohydrates. Ten percent carbohydrates is the bare minimum needed to prevent severe ketosis, a condition in which the blood becomes abnormally acidic from ketones, the byproduct of burning fat for fuel instead of glucose.

The Harvard-led group, comprising heart experts, nutritionists and biostatisticians, had its standards: The diets needed to include 8 percent or less of saturated fat, at least 20 grams of dietary fiber per day, and 150 mg or less of cholesterol per 1,000 kcal. The Atkins diet, the group determined, wasn't conducive to that.

Real world dieting

To be fair, the same is true about extreme low-fat diets. In the real world, these are hard to follow and become dangerous. In the Atkins regime, there is the temptation to sway from the precise Atkins recipe for success (which has changed over the years) and to consume protein high in saturated fat, cholesterol and salt, which are all treacherous for cardiovascular health.

In extreme-low-fat diets there is the temptation to consume simple carbohydrates instead of complex carbohydrates, which raises the risk of insulin intolerance and diabetes.

The most sensible diet for total body health — for weight maintenance and organ and joint health — remains to be low in fat and high in complex carbohydrates mostly derived from plants, despite our hunger for fast results from fad diets.

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Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears each Tuesday on LiveScience.

When the human body kicks into high gear, the brain can run on recycled, alternative energy to make the whole system more efficient, scientists have discovered.

The body breaks carbohydrates from food into glucose, the primary fuel of muscles and the mind. When muscles work hard, they produce lactate as a byproduct. Though recent studies have shown that muscles can re-use the lactate as fuel, conventional wisdom holds that it can also build up in the form of lactic acid, reducing performance and causing pain.

The new research shows that the brain can switch to lactate during strenuous exercise, using the muscles' byproduct as backup fuel.

The researchers, in Denmark and The Netherlands, looked at existing studies that had compared the blood running to and from the heads of volunteers engaged in strenuous exercise. The blood on its way to the brain was found to contain considerably more lactate than blood flowing from the brain. Further investigation showed that the brain was not storing the lactate which had come from the muscles during exercise, but rather using it as fuel. In fact, the brain helped to clear lactate from the circulation, thereby leaving glucose to the muscles that need it for the hard work they were performing.

The finding helps explain why the brain is able to work properly when the body's demands for fuel and oxygen are highest, and it shows that the brain actually shifts into a higher gear in terms of activity. This opens doors to entirely new areas of brain research related to understanding lactate's specific neurological effects that could lead to new treatments for common brain ailments, the researchers said in a statement today.

The findings are detailed in the October issue of the FASEB Journal.

"From an evolutionary perspective, the result of this study is a no-brainer," said Dr. Gerald Weissmann, editor-in-chief of the journal. "Imagine what could have or did happen to all of the organisms that lost their wits along with their glucose when running from predators . They were obviously a light snack for the animals able to use lactate."

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One of the few proven methods for extending life spans is to keep calorie intake to a bare minimum, but new studies suggest that even moderate calorie restriction could have substantial health benefits.

Separate new studies suggest cutting calories, especially carbohydrates, might ward off or alleviate symptoms of Alzheimer's disease and diabetes.

In one study done on mice, researchers found that restricting caloric intake can calm or even reverse symptoms associated with Alzheimer's.

People afflicted with Alzheimer's have elevated levels of a protein called beta-amyloid. The protein builds up as a plaque inside the brain and disrupts brain cell activity.

Putting mice on caloric restriction diets reduced the amount of beta-amyloid in their brains. The reverse was also true: Eating foods high with calories and saturated fats was found to increase beta-amyloids.

The researchers think that caloric restriction promotes the activity of SIRT1, a protein known to influence a variety of functions, including metabolism and aging. SIRT1 is believed to activate other proteins, such as alpha-secretase, which are known to inhibit beta-amyloid buildup.

The study, led by Giulio Maria Pasinetti at the Mount Sinai School of Medicine, will be detailed in the July issue of the Journal of Biological Chemistry.

In another study, albeit a small one, researchers in Sweden report that a low-carbohydrate diet in humans can improve symptoms associated with type 2 diabetes and reduce the need for medication.

The researchers found that seven diabetic patients who switched from a low-fat diet to a low carbohydrate diet (20 percent carbs) for 22 months showed improvement in hemoglobin A1C, a marker for long-term blood-sugar levels in diabetes.

The study, led by Jorgen Vesti Nielsen from the Department of Medicine at Blekingesjukhuset in Sweden, is detailed online in the journal Nutrition and Metabolism.

The U.S. Food and Drug Administration recommends that out of a 2,000 calorie diet, 60 percent of the calories should come from carbohydrates, 30 percent from fat and10 percent from protein.

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