Harvard Women's Health Watch

Weight-loss drug review

Before you try these medicines, know what they can do and if they are really for you.

When you have an ear infection or strep throat, you take antibiotics to treat the infection. Yet try to "cure" obesity with a pill, and you'll only end up disappointed. Diet pills can promote modest weight loss—provided you're a good candidate and you use them correctly—but they aren't for women who just need to lose a few pounds, and they won't magically melt away fat.

"The biggest message that I try to relate to patients is that there is no magic bullet," says Dr. W. Scott Butsch, an instructor in medicine at Harvard Medical School and specialist in obesity medicine.

Weight-loss drugs explained

These medications are currently FDA-approved for weight loss:

  • Orlistat (Xenical) is a prescription drug that blocks a fat-digesting enzyme in your intestines, preventing you from absorbing some of the fat from the foods you eat. Xenical can be used long-term. It's also available in a lower-strength, over-the-counter version called Alli.

  • Phentermine (Adipex-P, Pro-Fast), diethylpropion (Tenuate), and phendimetrazine (Bontril, Adipost, Anorex-SR) suppress appetite—making you feel full so you eat less. They're only approved for three months of use, but some doctors prescribe them off-label for longer periods of time.

  • Lorcaserin (Belviq) was approved by the FDA in late June, making it the first new weight-loss drug to be introduced in more than a decade. Belviq suppresses hunger by stimulating a receptor for the chemical messenger serotonin, which regulates fullness and metabolism.

  • In July, the FDA approved another new weight-loss drug, Qsymia, which is a combination of phentermine and the antiseizure/antimigraine drug topiramate. Qsymia also suppresses appetite, and it appears to be more effective for weight loss than any other single drug. Patients on the highest dose lost up to 9% of their initial weight. Qsymia is not recommended for people with heart disease, overactive thyroid, or glaucoma.

These pills won't necessarily give you quick or dramatic weight-loss results. In studies, women lost about 5% to 10% of their initial body weight over a year on prescription weight-loss drugs. But to lose that much weight, you'll have to also watch your diet and exercise.

Herbal diet pills

In addition to regulated weight-loss medications are many unregulated herbal pills, which are often promoted with plump "before" and chiseled "after" photos in magazine ads and TV commercials. These products contain ingredients such as ephedrine, chitosan, guarana, cascara, and yerba mate.

Just like pharmaceutical diet pills, herbal diet remedies are meant to decrease appetite, reduce the absorption of fat from your diet, or stimulate metabolism. Though their claims may be impressive, their results often aren't. And, just because they're labeled "natural" doesn't mean they're safe. Many supplements can cause side effects, or include ingredients that aren't on the label.

Before buying any herbal remedy, talk to your doctor. Also check the FDA website (http://www.fda.gov/ForConsumers/ConsumerUpdates) for any safety alerts.

Are weight-loss drugs for you?

Your doctor may decide you're a good candidate for weight-loss drugs if you

  • have a BMI higher than 30 (the definition of obesity), or have a BMI higher than 27 along with health problems related to your weight—such as type 2 diabetes

  • are overweight and actively dieting and exercising, but are unable to lose weight.

Don't take weight-loss medications if you have a history of heart attack, stroke, irregular heartbeat, or overactive thyroid gland. You also don't want to be taking any medications that could interact with a weight-loss drug.

Finally, you'll need to consider with your doctor whether the risks of these drugs (which range from heart problems and liver damage to possible addiction) are worth the weight you'll lose. For some overweight or obese women, they may be. Losing just 5% to 10% of your body weight can help reduce disease risk factors such as high blood pressure, blood sugar, and cholesterol.

The future of weight-loss drugs

Weight-loss drugs are evolving, and the thinking behind them has changed in recent years. "Now we have a broader idea of some of the mechanisms involved in obesity," Dr. Butsch says. "We realize there is a very complex interaction of factors involved in weight regulation. For most people, the treatment for obesity is not as simple as going on a diet or increasing exercise. So medications have been developed differently in the last decade."

Dr. Butsch says the future of weight-loss medications will lie in pairing drugs that work together to enhance weight loss without causing unacceptable side effects. "The more we understand the complex physiology of body weight regulation, the more likely we'll be using a combination of medications in the treatment of obesity," he says. "We're only at the tip of the iceberg in our knowledge of weight regulation."