Last updated: Dec 22, 2008
You buy wheat bread, watch the sweets, and have sworn off supersizing. But you still might be falling prey to some common diet myths. Read on to find out about the worst ones, and what you can do to outwit them.


1. Myth: Cutting carbohydrates helps you lose weight.
Truth: Doing it the wrong way can also make you feel rotten and unhealthy.
Carbs are to this decade what fats were to the last: food demons. Truth is, though, you need them for energy. And, like with fats, some are better than others. Lona Sandon, RD, assistant professor in clinical nutrition at the University of Texas Southwestern Medical Center, suggests a minimum of 130 grams of carbs a day—a far cry from low-carb diets that start with 20 grams or less.

"Levels that low can leave you fatigued, constipated, and irritable," she says. And those are just the short-term side effects. Eric Rimm, associate professor of epidemiology and nutrition at the Harvard School of Public Health, believes that long-term, an Atkins-style diet could increase risk of heart disease and colon cancer, perhaps due to the resulting increase in saturated fats.

Fad diets aside, what may matter most is how refined the carbohydrates are. Refining removes grains' fibrous coating, which leads to digesting food faster than you should. That's why whole fruits, with their fiber and nutrients, are good choices despite their simple carbohydrates. The best idea is to cut back on refined carbs such as soda and foods made with white flour, while loading up on healthier carbs like whole grains, fruits, and vegetables.




2. Myth: Diet foods help you drop pounds.
Truth: They can actually do the opposite.
You may be doing yourself more harm than good by scanning labels for the lowest calorie and fat counts. "They may be less caloric, but they're not necessarily better for you," Sandon says. "Prepackaged diet foods can have a lot of sugar and trans fat."

As with carbs, it's the quality of the fat, not the amount, that makes the difference. Monounsaturated fats (found in nuts, olive oil, and avocados) and the polyunsaturated variety (in corn, soybean, and safflower oils) help your cardiovascular system, improve weight loss, and are crucial for absorbing beta carotene from vegetables like carrots. Trans fats and saturated fats, on the other hand, have been linked with heart disease and even cancer.

The Harvard Nurses' Health Study vividly contrasts "good" and "bad" fats. It found that replacing just 30 calories of carbs a day with the same amount of trans fats nearly doubled the risk of heart disease. Replacing the same ratio of carbs with monounsaturated or polyunsaturated fats, on the other hand, lowered the risk of heart disease by 30 to 40 percent. So consider boosting your good fats by adding nuts to your morning cereal or some avocado to your salads. Just watch your overall daily calories to keep them in check.





3. Myth: The more you cut calories, the more weight you'll lose.
Truth: That can actually hurt you.
Cut your calories too far—below 1,200 a day—and you'll end up with a double whammy that quickly decreases your metabolism and muscle mass, Sandon explains. To get the most out of the calories you do eat, she suggests that you choose whole foods such as produce, fresh meat and fish, and whole grains that are as close to their natural state as possible. They have a higher "nutrient density" than refined foods, because they pack more vitamins and minerals into fewer calories.

4. Myth: Dairy makes you fat.
Truth: Cutting dairy just shoots you in the foot (and fat cells).
Ask most dieters for a definite no-no (pre-Atkins, anyway), and cheese will top the list. But that's "shooting yourself in the foot," says Michael Zemel, PhD, a University of Tennessee professor of nutrition and medicine, and author of The Calcium Key (John Wiley & Sons).

Combined with calorie control, a dairy-rich diet can nearly double body-fat reduction and weight loss and help prevent weight gain, he says. Part of the reason is the hormone calcitriol, which helps conserve calcium for stronger bones while telling fat cells to convert less sugar to fat and burn more body fat. The result is leaner fat cells and a leaner you. So we advise sticking to the government's latest dietary guidelines, which recommend three servings of low- or nonfat dairy a day. A cup of milk or yogurt, or 1 1/2 ounces of cheese equals one serving.




5. Myth: Brown equals whole-grain.
Truth: There are lots of whole-grain poseurs out there.
"People buy caramel-colored wheat bread and think they're getting a whole-grain product," Harvard's Rimm says, "but that's not always the case."

He advises looking for labels where "whole-wheat" or "whole-grain" top the list. It's worth the extra effort: More and more research is finding that whole grains reduce your risk of many chronic ailments, from obesity and diabetes to cardiovascular disease. The extra fiber in whole grains is key. "It leads to satiety and reduces the speed with which the meal is absorbed," Rimm says.

In essence, fiber makes you feel full, which means you eat less. It also helps level out the peaks and valleys of insulin that a meal produces. An added boost: Whole-grain foods tend to be higher in vitamins B and E than refined grains. So forget those barely grainy cereals and breads, and switch to ones that are truly whole-grain (with at least 3 grams of fiber per serving), making sure you get the recommended three servings a day.