Are the New Generation of Diet Drugs Safe?

For much of the past century, particularly in the ’60s, doctors prescribed powerful, addictive amphetamines to women to control their weight. As recently as 2010, the FDA took one of the few remaining weight drugs, Meridia, off the market because it was found to increase risk of heart attack and stroke. Prior to that came the fen-phen craze of the 1990s, when hordes of patients popped the fenfluramine-phentermine combo that had a powerful weight-loss effect—along with a 20 percent risk of developing potentially lethal heart-valve injury if you stayed on it long enough. Hundreds of reported cases of heart disease and a handful of deaths later, diet drugs in general lost their place in the market and their hold on our imagination.

So why do obesity specialists and the pharmaceutical industry think they’ve now finally got it right?

“Well, let’s say we’re getting it righter,” says Boston University’s Caroline Apovian, MD, who directs Boston Medical Center’s weight-loss program. “We have a better understanding of the physiology of weight gain, and we have drugs that hit more weight-specific pathways in the body.” The other reassuring thing is that two of the four new arrivals, Qsymia and Contrave, are novel combinations of drugs that have been prescribed for years for problems other than obesity. (Qsymia, which contains the amphetamine-like phentermine, should not be taken by anyone with heart disease.)


Before the FDA would approve the new drugs for weight loss, it required that at least one-third of the subjects taking them in clinical trials in conjunction with a diet and exercise regimen lose at least 5 percent of their total body weight. Five percent may not sound like the stuff of infomercial dreams, but as anyone who has tried to keep weight off will tell you, it’s not nothing. (Using the FDA’s data for Contrave specifically, we might estimate that Pyle lost an extra seven pounds due to the drug—but short of putting a clone of her on the same weight-loss program minus the drug, we can’t be sure.) Obesity experts who are bullish on diet drugs say that many people whose bodies respond to a given drug do better than that, and doctors often prescribe different meds until the most effective one is found.

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