Vyvanse: The pill you shouldn't use to lose weight

The Food and Drug Administration (FDA) recently approved Vyvanse (lisdexamfetamine dimesylate), a drug widely used for attention deficit hyperactivity disorder, to help curtail something else entirely—binge eating in adults. That might give you the impression that taking Vyvanse is a good way to drop some pounds. But the FDA makes clear—and our experts agree—that this stimulant medication should not be used as a diet drug.

For starters, "binge eating disorder" is not the same thing as eating too much. People diagnosed with this disorder experience episodes—often several times a week—where they report feeling out of control and compulsively overeat until they are uncomfortably full. Many report feeling embarrassed afterward and may avoid other people due to shame over how much they've eaten in a relatively short period of time.

Binge eating has been recognized as a serious problem for some time, but was only officially classified in 2013 as a disorder like anorexia or bulimia nervosa. Because there wasn't another FDA-approved drug treatment for binge-eating, the agency agreed to fast-track Vyvanse through the approval process. And, although the agency often asks an independent panel of experts to review evidence on older products put to new use, they opted to skip that step in this case, noting that Vyvane's safety record as an ADHD drug was sufficiently reassuring.

Find out why you should skip weight loss drugs, too, and what's wrong with herbal remedies.

Ultimately, the agency approved the drug based on two 12-week clinical trials involving a total of 724 people with the disorder. Those studies showed that on average, people were binging less by the end of the study—regardless of whether they took the drug or a placebo (sugar pill). However, people who took a 50- or 70-milligram dose of Vyvanse reduced the number of binge episodes more than those who took a 30-mg dose or a placebo. It's not clear if the desire to binge eat resumes when people stop taking the drug, or if taking the drug for a longer period of time results in a higher risk of side effects. Test results from follow-up studies the FDA required won't be available for at least three years.

No good drugs, including Vyvanse, for weight loss

• benzphetamine (Didrex, Regimex, and generic)
• diethylpropion (Tenuate and generic)
• phendimetrazine (Adipost, Bontril, Melfiat, and generic),
• phentermine (Adipex-P, Ionamin, Fastin, and generic).