10 Diet Lies

You've heard countless weight-loss claims: Drink coffee and get skinny. Eat fiber to beat bloating. But how many of these methods will really help you slim down? Before you invest time and money testing them, find out what experts have to say.

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Fiber

Claim: Eat fiber snacks and flatten your belly in 24 hours. Fiber acts like a sponge in the stomach, soaking up liquids and whisking them out of the body to smooth your tummy.

Truth: Eating enough fiber helps prevent constipation and reduces your risk of heart disease and other illnesses. "It can also help you lose weight in the long run, but it won't reduce your waistline in a day," says Susan B. Roberts, PhD, professor of nutrition at Tufts University. "You may even look bigger because fiber can bloat you."

Magnetic Earrings

Claim: Wearing magnetic earrings reduces hunger and food cravings. These earrings act on an acupressure point in the earlobe to dull taste and increase production of hormones that regulate cravings. You can lose 10 percent of your weight in nine weeks.

Truth: "There is no evidence of a biological basis for magnetic earrings affecting weight loss," says Richard Cleland, assistant director of the Federal Trade Commission's Division of Advertising Practices. "In 10 years working in this area, I have not seen a study that suggested an efficacy. A few years ago jewelry was reviewed in a scientific workshop examining weight-loss claims. The experts could find no feasible reason to believe it works."

Chromium Level

Claim: Increasing your chromium level can help you slim down. Chromium deficiency impairs the body's ability to digest carbohydrates and regulate blood-sugar levels. This can lead to weight gain, fatigue, and other health problems. Ingesting more chromium revs metabolism, helping you burn fat.

Truth: Insulin helps regulate appetite, blood-sugar levels, and fat production. Taking chromium, a common element found in many foods, may help improve insulin function in people with diabetes and glucose intolerance. "There is conflicting evidence," says Robert Saper, MD, MPH, director of Integrative Medicine at Boston University School of Medicine. "But there are no convincing findings that taking chromium leads to weight loss," says Dr. Saper, coauthor of a 2004 review of research on various diet supplements.

Diet Soft Drinks

Claim: Drinking more diet soft drinks helps you lose weight. People who start drinking more diet sodas usually drink fewer sugar-sweetened ones. By replacing one with the other, they cut calories and shed pounds.

Truth: A review of data from Harvard University's Nurses' Health Study II found that women who increased consumption of diet soda over a four-year span gained less weight than those who cut down on how much they drank, but they still gained. A review of data from the San Antonio Heart Study found that while drinking either diet or regular soft drinks correlated with weight gain, people who drank diet sodas were significantly more likely to gain. There are many possible reasons, says Sharon Fowler, MPH, who coauthored the review. It could be that diet-soda drinkers who gained weight had started gaining before the study began, switched to diet drinks to try to lose, but kept gaining for other reasons. Some people also drink diet sodas and then indulge in other ways. There's some evidence, though, that diet drinks may increase cravings and food intake. "We can neither confirm nor rule out that the diet drinks were actually causing people to gain," says Fowler, a faculty associate in clinical epidemiology at the University of Texas Health Science Center. "If they were, though, drinking as little as one diet drink a day may put a person at increased risk."

Coffee

Claim: Coffee is a weight-loss drink. Drinking two cups a day can reduce appetite and make workouts feel less taxing, helping you exercise longer and burn as much as 31 percent more fat.

Truth: "Caffeine or coffee alone has not been demonstrated in rigorous trials to reduce appetite," says Dr. Saper. Research shows, though, that drinking caffeine can increase endurance, helping you exercise longer. Researchers aren't sure why.

Fitness Water

Claim: Water and "fitness water" prime the body for weight loss. Drinking water boosts metabolism, staves off hunger, and prevents fatigue, protecting you from overeating when tired. The vitamins and minerals in fitness water also help keep your body's fat-melting systems functioning well.

Truth: "Ha, ha, ha," says William Rumpler, PhD, a research physiologist with the U.S. Department of Agriculture's Diet and Performance Laboratory. Translation: If just drinking regular or fitness water did all that, we'd all be thin.

Yeast

Claim: Eating less yeast can help you lose up to five pounds a week. Too much yeast in the system can cause bloating, fatigue, mood swings, cravings, lower metabolism, and weight gain. Getting yeast levels under control through a diet low in sugars and high in yogurt, broccoli, garlic, and other vegetables and protein can reverse these effects and speed weight loss.

Truth: It's nonsense to claim that lowering yeast levels causes the body to shed fat, says Jack Sobel, MD, chief of the Division of Infectious Diseases at Wayne State University School of Medicine in Detroit. It's also silly to claim that eating alkaline vegetables, yogurt, or garlic can retard yeast growth. Taking antibiotics can trigger yeast infections. Taking birth control pills can also cause them on rare occasions. "A diet high in sugar can trigger them in women who are already susceptible," says Dr. Sobel. "But for everyone else, sugar consumption has no effect on yeast. And it's nonsense to say that yeast infections cause weight gain, carb cravings, low energy, or mood swings."

Selenium

Claim: Taking selenium revs metabolism, helping you drop pounds. Stress, illness, or bad nutrition can overwork the thyroid and adrenal glands, causing low energy, slow metabolism, and weight gain. Taking 200 micrograms of selenium daily can dramatically improve glandular function and increase energy and calorie burn.

Truth: Low thyroid function can result in slower metabolism and weight gain. But it isn't caused by stress, illness, or bad nutrition. It is usually caused by an autoimmune disorder, congenital defect, hormonal problem, or damage to the thyroid. As for selenium, "We know it is an essential component of enzymes that activate and deactivate the thyroid hormone," says Wayne C. Hawkes, PhD, a research chemist with the USDA/ARS Western Human Nutrition Research Center. "But there's no evidence that taking supplements will improve thyroid function and help you lose weight." In one study Dr. Hawkes found that men taking high levels of selenium (297 micrograms daily) began gaining weight, while those taking low doses (14 micrograms) began to lose. This suggests that taking high doses, if it has any effect, may cause a mild form of low thyroid function, the condition it's supposed to cure.

Cranberry Juice

Claim: Cranberry juice is high in antioxidants that help maintain the skin's connective tissue and prevent cellulite from forming. Drinking eight ounces daily can significantly diminish dimpling in just three weeks.

Truth: Cranberries are rich in a class of antioxidants called proanthocyanidins that help prevent bacteria from sticking to cells. "This means less dental plaque, fewer ulcers, and fewer urinary tract infections," says Amy Howell, PhD, a research scientist at Rutgers University's Marucci Center for Blueberry and Cranberry Research. Proanthocyanidins also help maintain connective tissue. "But there are no studies of any kind showing any relationship between cranberries and cellulite," says Dr. Howell. Drinking 10 ounces of cranberry juice daily can help prevent bacterial infections, but it won't do a thing for your thighs.

HCA

Claim: Ingesting HCA can reduce fat-cell formation by 70 percent for up to 12 hours after a meal. A compound called hydroxycitric acid (HCA) found in the juice and rinds of citrus fruits inhibits the action of an enzyme that converts blood sugar to fat, reducing the body's ability to create new fat cells.

Truth: HCA can impede the formation of fat cells in a test tube, but it's unclear whether it works the same way in humans. "At this point the evidence is contradictory," says Dr. Saper. It's also unclear whether most citrus juices and rinds even contain HCA, which is found primarily in the purple Malabar tamarind, a tropical fruit native to India.