July 12, 2004 -- There's no question that losing weight is one of the best ways for people with type 2 diabetes to manage their disease. The question is, how much weight can be shed by obese people with type 2 diabetes with the aid of FDA-approved weight-loss drugs such as Xenical and Meridia?
The answer: Less than if they had taken Prozac for the same amount of time, according to a new study.
After reviewing previously published studies involving more than 2,000 obese people with type 2 diabetes, researchers report that those taking Prozac lost twice as much weight as patients taking Xenical for one year -- nearly 13 pounds compared with Xenical's 6 pound weight loss.
The popular antidepressant also may have edged out Meridia, producing an average weight loss of slightly more than 11 pounds in patients taking Prozac for 24 to 30 weeks, compared with less than 10 pounds shed after 26 weeks by those using Meridia.
No Magic Bullet
"We showed fairly modest effects with all these drugs," lead researcher Susan L. Norris, MD, MPH, of the CDC's Division of Diabetes Translation, tells WebMD. "While we were hoping for some magic bullet, clearly these drugs are not that."
Instead, her review of studies previously done on how these medications can help obese diabetic patients lose weight confirms what researchers have long suspected: They have their place in the management of obesity in type 2 diabetes, but don't expect drastic improvement.
Still, the weight loss experienced by those taking each of the three drugs is enough to improve control of type 2 diabetes.
"A 10-pound weight loss from medications will improve glycemic control and will have positive effects on lipids and blood pressure if it's sustained for the longer term," says Norris. "A 10-pound weight loss in someone who is obese and has diabetes is clinically significant."
Weight Loss Harder for Diabetic Patients
That's because patients with type 2 diabetes typically lose less weight using these drugs or with other weight-loss strategies than people without diabetes, says David E. Kelley, MD, an endocrinologist and director of the University of Pittsburgh Obesity and Nutrition Research Center, who did his own study of Xenical in the treatment of diabetes.
"As people with diabetes start to lose weight, their glucose values tend to fall toward the normal range -- and that's desirable," he tells WebMD. "When they lose a little weight and come under (disease) control, there is a stronger set of metabolic factors to plateau their weight loss sooner. So in a way, people with diabetes have to diet and exercise twice as hard to keep on losing weight."
Still, Kelley says he was "surprised" that the patients taking Prozac had more weight loss than those on the weight-loss medications.
Norris says it was the large number of participants in of one study, in particular, that gave the edge to the most widely prescribed antidepressant in the U.S., which suppresses appetite. In fact, although not widely touted for that purpose in the U.S., Prozac and other antidepressants are sometimes pitched as "diet pills" in Europe.
Long-Term Effects Uncertain
For her study, published in today's Archives of Internal Medicine, Norris' team focused on six studies on Prozac and four each on the two weight-loss medications, which are typically prescribed only after efforts to lose weight with diet and exercise have failed. In most of the reviewed studies, patients typically reduced their caloric intake by about 500 calories per day while some got the study medication and others got a placebo.
"While these drugs do produce modest weight loss, that could benefit patients with type 2 diabetes and lower their risk of cardiovascular risk factors," she tells WebMD. "But we only have data for using these drugs up to one year, so we're uncertain about the long-term effects."