All five prescription diet drugs on the U.S. market can help people lose enough weight to improve their health, researchers reported Tuesday.
The drugs, which all act in different ways to help people lose weight, have been approved over the past 17 years.
The drug that showed the most weight loss? One called Qsymia — a combination of an older appetite suppressant called phentermine and an anti-seizure drug called topiramate.
They work together in ways that are not fully understood to suppress appetite and 75 percent of people taking the drug lost at least 5 percent of their body weight, the review found.
Patients who took Qsymia lost more than 19 pounds on average after a year. People who took liraglutide, a diabetes drug sold under the brand name Victoza, lost almost 12 pounds on average, the team found, and 63 percent of those who took it lost at least 5 percent of their body weight — the amount that's been shown to lower the risk of diabetes and heart disease.
Victoza, which must be injected, helps the stomach empty more and changes how well the body uses insulin, which converts food into glucose.
Related: American Obesity Rates on the Rise
Next best was Contrave, a combination of buproprion, approved separately to treat depression and smoking, and the alcohol and drug abuse drug naltrexone. The two work together to suppress appetite by tweaking brain chemicals. Patients taking the pill, lost an average of 11 pounds over a year.
Lorcaserin, sold under the brand name Belviq, helped patients lose 7 pounds over a year. It also acts on brain chemicals to affect mood and appetite and 49 percent of patients who took it lost at least 5 percent of body weight.
Orlistat, sold both as Xenical and over the counter in lower doses as Alli, helped patients lose 5.7 pounds over a year on average. And 44 percent of patients who took it for a year lost 5 percent of body weight or more. Orlistat stops the gut from absorbing some of the fat in food.
The varying results likely mean different patients will be helped most by different drugs, said Dr. Rohan Khera of the University of Iowa Carver College of Medicine, who helped lead the study.
"Ultimately, given the differences in safety, efficacy, and response to therapy, the ideal approach to weight loss should be highly individualized, identifying appropriate candidates for pharmacotherapy, behavioral interventions, and surgical interventions," the team wrote in the Journal of the American Medical Association.
And, they said, they all need more study. "Short-term clinical trials may not provide comprehensive information on the long-term safety of these agents, and prospective postmarketing surveillance studies are warranted."
With more than two-thirds of Americans obese or overweight, the need is dire. The latest data from the Centers for Disease Control and Prevention shows that 38 percent of U.S. adults are obese.
Studies have shown that surgery helps people lose the most weight but the drawbacks are clear and it's very expensive.
The FDA has approved several new devices to help people lose weight - most lately, a stomach pump that was approved Tuesday.
Doctors are reluctant to prescribe weight loss drugs, in part because several were pulled off the market in the 1990s after they were shown to cause strokes and other serious side-effects. A study presented to the Endocrine Society earlier this year showed that only only 1 percent of obese patients eligible for prescription weight-loss drugs ever get prescriptions for them.
Khera's team looked at 28 studies covering nearly 30,000 overweight or obese adults who got one of the diet drugs in a randomized trial - meaning people were randomly assigned to take either the drug or a placebo.
"All active agents were associated with significant excess weight loss compared with placebo at one year," they wrote.
Hardly any of the trials compared the drugs head to head, so it's difficult to say one works better than another, they noted.