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.
<a href="mailto:RobinNixon@hotmail.com">Robin Nixon</a>, LiveScience Staff Writer
Fat-free food leads to fat-free bodies.
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 <a href="http://www.livescience.com/health/8-reasons-overweight-fat-obesity-100330.html">national rise in obesity</a> 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
<a href="http://www.livescience.com/health/080506-hormone-tasty.html">hormone that makes us feel hungry</a>, while simultaneously spurring the release of peptides that make us feel full, found a study published in the<em>American Journal of Physiology, Endocrinology and Metabolism</em>in 2005. A moderate amount of fat can also lower the <a href="http://www.livescience.com/health/090107-brain-food.html">glycemic
index</a> of a meal, helping you feel satisfied for longer.
Energy bars will power weight loss.
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 <a href="http://www.livescience.com/health/060704_bad_raw_food.html">raw-food</a>
converts usually experience, explains Richard Wrangham in "Catching
Fire; How Cooking Made Us Human" (Perseus Books, 2009).<em> </em>
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,
Grazing will boost metabolism and help you lose weight.
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 <a href="http://www.livescience.com/health/080714-hunger-happy.html">hunger</a>
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.
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 <a href="http://www.livescience.com/health/061010_bad_trans_fats.html">trans
fat is truly evil</a>, saturated fat found mostly in animal products
performs many critical functions, such as helping the body use calcium
and <a href="http://www.livescience.com/health/061024_bad_fish.html">omega
3s</a>, boosting the immune system and protecting major organs from
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.
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 <a href="http://www.livescience.com/health/090106-exercise-obesity.html">exercising</a>,
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 <a href="http://www.livescience.com/health/080806-brain-exercise.html">protecting
your brain</a>, 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.
Alcohol, however, may be in a separate class, as far as liquid
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 <a href="http://www.livescience.com/health/091103-moderate-drinking.html">does
not promote alcohol</a> as a weight-loss tool. The study was published
in the March 2010 issue of the journal <em>Archives of Internal Medicine.
Juice detoxes, smoothies and diet sodas are effective weight-loss tools.
In our hunter-gatherer days, "we didn't have a lot of <a href="http://www.livescience.com/health/090406-liquid-calories.html">liquids
with calories</a>, 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, <a href="http://www.livescience.com/health/090512-soda-tax.html">sodas</a>
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 <a href="http://www.livescience.com/health/070515_bad_sugar.html">artificial
sweeteners</a> are more likely to gain weight, according to a study
published in the journal <em>Obesity</em> 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