Do Weight-Loss Supplements Actually Hurt Your Waistline?

Having trouble losing weight? Taking a diet pill isn't the answer. In fact, it may be part of the problem, reports a new study in Appetite.

Researchers asked 74 participants to take a pill; half were told the pill was a weight-loss supplement, while the other half were told it was a placebo. Turns out, they were actually all placebos. But when each group was given a bowl full of chocolate, the people who thought they'd taken a supplement ate more pieces of candy than the other group.

The likely reason: People taking supplements may feel as if they're already contributing to their weight-loss goals, and, therefore, may not be as strict  with their food choices, says study author Wen-Bin Chiou, a psychology professor at National Sun Yat-Sen University in Taiwan. It's called the "licensing effect," a psychological phenomenon that allows people to rationalize a bad behavior as long as they do something good first.

The effect happens with more than just weight-loss pills, too. In previous studies, Chiou found that subjects who thought they'd taken a multivitamin consistently acted in less healthy ways—like exercising less or smoking cigarettes more—than participants who knew they took a placebo.  (Find out more about the dark side of the pills and potions you take in this special report on The Dangers of Supplements.)

Besides the chances of increasing your middle, a 2011 review in the Journal of Obesity found that weight-loss supplements might have no benefit at all. That means the best you can do is break even, which begs the question: Why spend money on pills that have no fat-fighting magic? Stick with things that can give you real benefits and set you up for potential success, like hitting the gym or chowing  down on a salad. (Don't take supplements with abandon.