Busting 10 Diet Myths

Myth No. 4: Coffee Can Help You Lose Weight

The theory: The caffeine in coffee acts as an appetite suppressant and a metabolism booster.

The reality: While coffee may temporarily squelch your appetite, drinking a couple of cups a day won't have enough of an effect to help you lose weight. Besides, pouring too much coffee into your system―drinking, say, four to seven cups a day―may lead to anxiety, sleeplessness, and an increase in heart rate and blood pressure.

The best advice: Enjoy a cup or two of coffee (or tea) every day, if you please. Just be sure that if you add anything to the brew―like cream, sugar, or cocoa powder―you take those calories into account. For example, a 16-ounce Starbucks Café Mocha can contain a whopping 330 calories (60 more than some chocolate bars). What's more, those calories might not make you feel as full as the same number of calories eaten in solid form. Another coffee concern: sleep disruption, which new evidence reveals is linked to weight control. "Every time people feel tired, they think, I have to have a latte," says Liz Applegate, Ph.D., director of sports nutrition at the University of California, Davis. "They become addicted to caffeine on a higher level, and it takes four to six hours to clear out of the system. Sleep is not as good, and you're tired the next day." And probably hungrier, too. At least two studies have shown that when people are sleep-deprived, they produce more of the hormone ghrelin, an appetite stimulant, and less leptin, an appetite suppressant. Not to mention that your resistance to the doughnut's siren song is a whole lot lower when you're pooped.