If you've ever seen an ad for a weight-loss supplement and thought it sounded too good to be true, that's because it probably is. Losing weight requires more effort than popping a few pills. And even if you do drop a few pounds using diet pills, the risks and adverse side effects aren't worth it. A healthy diet combined with exercise can help you lose extra pounds and will lead to more successful and long-term weight loss.

Risks and side effects

Consumers Union, the nonprofit publisher of this Web site, has long cautioned against the use of weight-loss supplements for reasons of safety and efficacy. Ingredients that might seem harmless, such as caffeine and bitter orange, can lead to potentially dangerous increases in blood pressure and heart rate when combined, as they are in Xenadrine EFX and CortiSlim diet pills. No diet supplement has consistently demonstrated in solid clinical trials that it can safely help people shed weight. And since most manufacturers now recommend combining their products with a healthy diet and exercise, the pills may make little or no difference.

The prescription weight-loss drug sibutramine (Meridia) produces, at best, only modest weight loss compared with regular dieting and has also been shown to elevate heart rate and blood pressure, especially in patients at risk for heart disease. Sibutramine also should not be used by people with eating disorders, patients taking medication for depression, or those with a history of seizures, liver disease, or other serious diseases and conditions. As always, talk with a doctor about any health problems you may have or medications you're taking before trying this drug, and consider diet and exercise instead.

Diet pills can also cause embarrassing and uncomfortable side effects. For example, a fat-blocking drug called orlistat, which may make a marginal difference in weight loss when taken at prescription strength and even less in its over-the-counter version Alli, has common and unpleasant intestinal side effects that may make you want to stay close to a bathroom.

False claims

The marketers of some of the most popular products, including CortiSlim, CortiStress, One-A-Day WeightSmart, TrimSpa, and Xenadrine EFX, were charged with making false or unsubstantiated claims in January 2007. Ads for Xenadrine EFX, for example, said the pill was clinically proven to cause rapid and substantial weight loss. But according to the Federal Trade Commission, studies commissioned by Xenadrine's manufacturer failed to support the claim—and one study showed that people lost more weight with a placebo. Claims by the makers of CortiStress that their product had the potential to spur rapid weight loss and reduce the risk of conditions such as cancer and Alzheimer's disease were also unsubstantiated, the FTC said.

Now, two years later, even more manufacturers of weight-loss products have been accused of false advertising by the FTC. They include a patch called Peel Away the Pounds, Questral AC, Questral AC Fat Killer Plus, Rapid Loss 245, Rapid Loss Rx, Slim Coffee, and Zyladex Plus.

But diet pills remain popular. In a recent survey sponsored by the pharmaceutical company GlaxoSmithKline and conducted by the University of Connecticut, 3,500 people in the U.S. were asked about their use of dietary supplements for weight loss and if they thought the products were safe, effective, and scrutinized by the Food and Drug Administration (FDA) before they went on the market. Among the adults who made a serious effort to lose weight, 34 percent said they had tried a weight-loss supplement. And many mistakenly thought that the FDA regulated the supplements before they appeared on retail shelves.

Because dietary weight-loss supplements are categorized as nutritional supplements, the FDA treats them differently than drug products. Companies that produce the weight-loss supplements are responsible for making sure they are safe and that their claims are truthful before they go to market. The FDA is responsible for taking action if the products are shown to be unsafe or if the claims are false. And all weight-loss supplement labels must prominently state that the FDA has not evaluated the product and its claims about weight loss. So, buyer beware.

CR's Take: Discuss any weight-loss product with your doctor. Consider losing weight with supervised diet and exercise programs based on a heart-healthy diet.