Over-the-counter weight-loss pills: Do they work?

The temptation to use over-the-counter weight-loss pills to lose weight fast is strong. But are these products safe and effective? By Mayo Clinic Staff

The appeal of losing weight quickly is hard to resist. But do weight-loss pills and products lighten anything but your wallet? And are they a safe option for weight loss? Here's a look at some over-the-counter weight-loss pills and what they will and won't do for you.

Over-the-counter doesn't mean risk-free

A number of weight-loss pills are available at your local drugstore, supermarket or health food store. Even more options are available online. Most haven't been proved effective, and some may be downright dangerous.

Dietary supplements and weight-loss aids aren't subject to the same rigorous standards as are prescription drugs. Thus, they can be sold with limited proof of effectiveness or safety. Once a product is on the market, however, the Food and Drug Administration (FDA) monitors its safety and can take action to ban or recall dangerous products. Indeed, the FDA has banned the sale of supplements containing ephedra and other ephedrine-like ingredients.

Check the facts before you buy

It's important to do your homework if you're thinking about trying over-the-counter weight-loss pills. Read labels and talk with your doctor or pharmacist. Also be sure to check the FDA website for alerts about safety concerns and product recalls.

The table shows common weight-loss pills and what the research shows about their effectiveness and safety.

ProductClaimEffectivenessSide effects
Alli — OTC version of prescription drug orlistat (Xenical) Decreases absorption of dietary fat Effective; but weight loss is even more modest than that with Xenical Loose stools, oily spotting, frequent or hard-to-control bowel movements; reports of rare, but serious liver injury
Bitter orange Increases calories burned Probably ineffective Similar to ephedra: raised blood pressure and heart rate
Chitosan Blocks absorption of dietary fat Probably ineffective Uncommon: upset stomach, nausea, gas, increased stool bulk, constipation
Chromium Decreases appetite and increases calories burned Probably ineffective Uncommon: headache, insomnia, irritability, mood changes, cognitive dysfunction
Conjugated linoleic acid Reduces body fat Possibly effective Upset stomach, nausea, loose stools
Green tea extract Decreases appetite, and increases calorie and fat metabolism Insufficient evidence to evaluate Dizziness, insomnia, agitation, nausea, vomiting, bloating, gas, diarrhea
Guar gum Blocks absorption of dietary fat and increases feeling of fullness Possibly ineffective Abdominal pain, gas, diarrhea
Hoodia Decreases appetite Insufficient evidence to evaluate Insufficient information available
Sources: U.S. Food and Drug Administration, 2011; Natural Medicines Comprehensive Database, 2011
Feb. 11, 2012 See more In-depth