Share

• DIGG
• DELICIOUS
• LINKEDIN
• FACEBOOK

Weight-loss aids: Buyer beware

According to a 2004 review in American Family Physician, Americans spent more than $1.3 billion on weight-loss supplements in 2001. Advertisements for weight-loss supplements seem to be everywhere — television infomercials, popular magazines, even your e-mail inbox. "Eat the foods you love and still lose weight" and "Exercise in a bottle" are among the marketing ploys that sound too good to be true. And, for the most part, they are.

Take a look at the fine print on these products for the disclaimer that none of their statements have been verified by the FDA, which is responsible for ensuring the safety of all foods and medications on the market. In the case of medications, the FDA is responsible for testing effectiveness. For example, a cold medicine that claims to relieve nasal congestion must be proven to do so. However, weight-loss aids fall into a gray area in FDA regulation.

Weight-loss aids are neither foods nor drugs; rather, they are classed as dietary supplements. Congress created the category of dietary supplements under the Dietary Supplement Health and Education Act of 1994, in response to public pressure to loosen the FDA's tight control over a variety of products. As a result, individual nutrients, herbs, and "phytomedicinals" (plants supposed to have medicinal value) can be sold without being tested for effectiveness or safety, so long as they do not make direct health or therapeutic claims. Within these limits, manufacturers cannot say that their weight-loss aids will cure obesity or make you lose weight, but they can make indirect claims — and this has led to a wide array of unfounded assertions on labels and in advertisements.

Some manufacturers of dietary supplements have been fined for false advertising. In 2006, the Federal Trade Commission ordered sellers making questionable weight-loss claims for skin gels and diet supplements to pay $3 million to settle fraud charges under federal law. For example, the skin gel ads claimed the gels would melt away fat wherever applied — on a user's thighs, tummy, and even double chin.

But the FDA cannot take a product off the market unless it is found to be unsafe. Because the agency cannot test every one of the thousand supplements on the market, most face no danger of being removed.

In 2004, however, the FDA banned the sale of ephedra (Ma huang in Chinese) after the compound was linked to a number of deaths and very serious side effects, including heart attacks, strokes, and seizures. In 2001, ephedra products comprised fewer than 1% of all dietary supplement sales, yet they were responsible for 64% of all herb-related complications reported to the U.S. Poison Control Centers during the same year. Despite the fact that ephedra-containing supplements are the only dietary supplements shown to help people lose weight (at least for up to six months), the potential risks far outweigh the benefits.

Despite the ban on ephedra itself, supplements containing ephedra-like compounds (which include ephedrine, norephedrine, and methylephedrine) are widely available over the Internet and in stores. They are often found in combination with caffeine or plant sources of caffeine, such as guarana and yerba mate, in weight-loss supplements. Note that two other ingredients found in some supplements, bitter orange and country mallow, contain chemicals related to ephedra and should also be avoided.

You should also steer clear of chitosan and guar gum, two more compounds found in weight-loss supplements. That's not because of any evidence that they are unsafe, but rather because studies show they don't help people lose weight. The FDA has also deemed spirulina (blue-green algae) ineffective for weight loss, and no information about its safety is available.

What about the approximately 50 other different substances found in weight-loss supplements? The evidence as to whether they work is unclear, because study results are either insufficient or conflicting. And although some of them appear to be safe, others have unknown safety profiles. As a result, the authors of the American Family Physician study (all doctors at Harvard Medical School) say that people should be cautious about using any of these supplements. Table 3 summarizes their advice on common weight-loss supplements. You should let your doctor know if you choose to take one, and alert him or her immediately if you experience any side effects.

Back to top

Review Date: 2006-09-01

Harvard Medical School does not endorse products or services.