The Skinny on the New Weight-Loss Drugs

Weight Loss Drugs

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After more than a decade, the Food and Drug Administration (FDA) has approved not just one but two new drugs for weight loss, both in the last month. Neither of these medications is a game-changer–they promote only modest weight loss, and although they appear to be safe, there is still concern about long-term risks given the unfortunate experience with fenfluramine, a weight loss drug (no longer on the market) that was associated with heart valve damage. Nevertheless, for a small proportion of the overweight and obese population, these medications may offer a useful middle ground between simple lifestyle management and the more drastic bariatric surgery.

Because of the concerns about the safety of weight-loss drugs, the FDA’s decision to approve these medications has been controversial. However, because of the growing obesity epidemic–currently, roughly one-third of Americans have a Body Mass Index (BMI) over 30, the threshold for obesity, and by 2030, nearly half the population is expected to be obese–the FDA concluded that the potential benefits of approval outweighed the risks.


Lorcaserin (marketed as Belviq), the first of the two new drugs to be approved, promotes weight loss by inducing an early feeling of satiety. The weight loss in clinical trials wasn’t profound, averaging a little more than 3 percent of body weight (which translates to 5.4 pounds for a 180-pound person) in patients who took the drug compared to those who took a placebo, although a third of patients lost more than 5 percent of their weight (9 pounds for a 180-pound person). The side effects were minimal, and only headache was more common in the treated group. Concerns about heart valve damage and cancer risk have so far proven unfounded.


The second drug, Qsymia, is a combination of two medications that have been around a long time: phentermine, an appetite suppressant, and topiramate, used primarily to treat seizures and prevent migraine headaches. Qsymia appears to be more effective than lorcaserin, producing a weight loss of over about 9 percent of body weight after one year when taken in high doses, with two-thirds of patients losing at least 5 percent of their body weight. However, there’s more concern about the dangers of Qsymia than there is about Belviq–in clinical trials for Qsymia, side effects included elevated heart rates and cognitive problems in some people. There’s also an increased risk of birth defects if taken during pregnancy. Other side effects include tingling in the hands and feet, insomnia, altered taste, constipation, and dry mouth.

Consider These Criteria

The FDA recommends that Belviq and Qsymia be considered an option only for people whose BMI is at least 30 (about 210 pounds for a 5-foot-10 person). The administration also suggested lowering the BMI threshold to 27 (about 175 pounds for a 5-foot-10 person) for people with weight-related medical problems such as high blood pressure, high cholesterol, type 2 diabetes or sleep apnea. Women of childbearing age should have a negative pregnancy test before starting on Qsymia, and patients with hyperthyroidism, glaucoma, unstable heart disease, or patients who have experienced a recent heart attack or stroke shouldn’t take either medication.

Talk to Your Provider About Risks and Benefits

So should you start taking Belviq or Qsymia if you’re overweight or obese? That’s a difficult question, especially since we still have only a preliminary understanding of their benefits and risks. These drugs are by no means cures for obesity, and need to be taken continuously in order to produce lasting results–if you stop taking either of the drugs, you’re likely to regain any weight you lose while on it–but the risks of long-term usage are simply unknown. Clearly, healthy eating and exercise remain the best approaches to weight loss.

If you’re curious about either of these medications, we encourage you to meet with your primary care provider to discuss the available information, as well as alternative approaches to weight loss, and make an informed decision.

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The One Medical blog is published by One Medical, an innovative primary care practice with offices in Boston, Chicago, Los Angeles, New York, Phoenix, the San Francisco Bay Area, Seattle, and Washington, DC.

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