7 Biggest Diet Myths

Diet Myths

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Bathing suit season is just around the corner and every friend has a new diet tip. But does science back them up? Here are some of the most popular diet myths that make scientists shake their heads.

Robin Nixon, LiveScience Staff Writer

Fat-free food leads to fat-free bodies.

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In the 1980s, new dietary recommendations came out imploring everyone to adopt low-fat diets. Only recently has it become clear what a mistake that was. Calling the recommendation an "uncontrolled experiment on a whole population," Dr. Michael Alderman said low-fat diets might have helped spur the national rise in obesity and diabetes.

We now know that fats are necessary for health. Fat is critical for the optimum functioning of the brain, the heart, the skin and other major organs, as well as for the absorption of many vitamins.

They are also good for dieting. Fat digestion suppresses ghrelin, the hormone that makes us feel hungry, while simultaneously spurring the release of peptides that make us feel full, found a study published in theAmerican Journal of Physiology, Endocrinology and Metabolismin 2005. A moderate amount of fat can also lower the glycemic index of a meal, helping you feel satisfied for longer.

Energy bars will power weight loss.

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Power Bars, Zone Bars, MetRx and so on are all processed foods. And processed foods, almost to a rule, can sabotage even the most committed diet in part because they are so easy for our bodies to absorb.

Think of processed foods as partially digested foods. They allow our guts to laze about, conserve energy and encourage weight gain.

In contrast, whole foods can take a considerable amount of energy to digest. This expenditure likely explains the rapid weight loss raw-food converts usually experience, explains Richard Wrangham in "Catching Fire; How Cooking Made Us Human" (Perseus Books, 2009).

While most scientists, including Wrangham, do not recommend a diet completely composed of raw food, avoiding processed foods, even ones with aggressive health claims, will help you reach a healthy weight, Lippert said.

Grazing will boost metabolism and help you lose weight.

Chinese researchers have made headlines by genetically modifying a herd of 300 cattle to produce milk that is somewhat akin to human breast milk.

While going too long without eating can set you up for diet catastrophes, "grazing can also rack up calories," Lippert said. Handful after handful of almonds, or continuous sips of banana-soy smoothies, will eventually appear on your waistline, she said.

A grazing habit degrades a person's internal guidance about when to eat, making it nearly impossible to tap into hunger and satiety cues, Lippert said. "If you can't remember the last time you were really hungry, that is not a good thing," she said.

When we eat freely and continuously, in any place at anytime, we begin eating more for stimulation and reward, rather than responding to our bodies' needs, said Dr. David Kessler, former FDA commissioner and author of "The End of Overeating; Taking Control of the Insatiable American Appetite" (Rodale Books, 2009).

Such behavior is not good for anyone's diet.

Saturated fat causes cellulite, and it's bad for you anyway.

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Cellulite is no different than other body fat; some fat just gets stored as cellulite in some parts of the body. And any excess body fat is caused by excess calories, no matter whether those calories come from bacon, donuts or carrot sticks.

Past studies lumped saturated fat in with trans fat, giving the former a bad rap by association. But while trans fat is truly evil, saturated fat found mostly in animal products performs many critical functions, such as helping the body use calcium and omega 3s, boosting the immune system and protecting major organs from disease.

And, in small quantities, it can even help your diet. "You can blow through half a block of low-fat cheese, because it doesn't taste like anything," Lippert said. "But have a little full-fat cheese, and magically you are satisfied."

Rather than shunning saturated fat, scientists suggest the best eaters limit it to about 20 grams a day, a third of the recommended total fat intake. A small burger (3.5 ounces, 75 percent lean meat) has about seven grams of saturated fat, as does a pat of butter.

You can eat whatever you want, as long as you exercise.

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Exercise is not a very effective way to lose weight, researchers say. The amount of exercise needed to lose even a single pound — if diet is not rethought — is more than most people can do, Apovian said.

If you are just exercising, the scale is unlikely to budge, agreed obesity researcher Susan Carnell of Columbia University. "You can make a better impact by controlling what you eat."

But don't give up your exercise routine. In addition to a host of general health benefits, including protecting your brain, heart and bones, exercise is great for maintaining weight and regulating appetite, Carnell said. In fact, a daily habit of intensive exercise is the shared trait among once-overweight people who successfully stay slim, Apovian said.

Beer gives you a belly.

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Alcohol, however, may be in a separate class, as far as liquid calories go.

At 7 calories per gram, alcohol is what scientists call a "non-trivial" calorie source. (A gram of fat has 9 calories, while protein and carbs, including simple sugars, have 4 calories per gram.) So imagine their surprise when, in a 13-year study of 19,220 U.S. women, teetotalers were more likely to become overweight than women who regularly imbibed beer, wine or liquor.

The link remained even after accounting for a slew of lifestyle factors, including exercise habits, nutritional intake and smoking status. "We are quite confident that the association we observed is due to the biological effect of alcohol," lead researcher Dr. Lu Wang of Harvard Medical School told LiveScience.

She cautions, however, that the study followed women who were initially a healthy weight, and does not promote alcohol as a weight-loss tool. The study was published in the March 2010 issue of the journal Archives of Internal Medicine.

Juice detoxes, smoothies and diet sodas are effective weight-loss tools.

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In our hunter-gatherer days, "we didn't have a lot of liquids with calories, explains Dr. Caroline Apovian, an obesity researcher at Boston University. As a result, our bodies today interpret beverages as having fewer calories than they actually do and find them less satisfying than solid food and so we eat more to compensate.

Many scientists think non-diet beverage consumption — those with sugar — contributes to excess weight gain. And while often villainized, sodas are not the only culprits. Juices, smoothies and various "health drinks" can also confuse our internal calorie-counters and make weight difficult to control.

What about diet drinks? People who regularly slurp artificial sweeteners are more likely to gain weight, according to a study published in the journal Obesity in 2008. The most touted explanation for this finding is that fake sweeteners increase cravings for calorie-dense foods, but the science behind this theory is mixed. Still, if you want to play it safe while tightening your belt, stick to water.