Modest Results From Weight Loss Drugs

Nov. 15, 2007 -- Most dieters who take prescription weight loss medications lose only a fraction of the weight they want to lose, and many don't stick with the drugs, a review of the research shows.

When results from 30 trials were analyzed, long-term users of three widely prescribed weight loss drugs lost an average of 6 to 11 pounds over the course of one to four years.

Between 30% and 40% of the participants stopped taking the drugs before the trials ended.

Users of the drugs Xenical, Meridia, and the unapproved drug Acomplia did lose more weight than dieters who took placebos.

They were also more likely to lose 5% to 10% of their body weight -- an amount that is recognized for reducing the severity of obesity-related risks such as  diabetes, heart disease, and other weight-related health problems.

But Raj Padwal, MD, of the University of Alberta, says most people who take weight loss drugs are hoping to lose much more weight than the studies suggest they do.

"People tend to be disappointed with the degree of weight loss they achieve with these drugs, even when they know that modest weight loss will improve their health," he says. "People who are desperate to lose weight are usually willing to try drugs, but if they don't see the results they want in two or three months they don't tend to stay on them."

Pros and Cons of Weight Loss Drugs

The trials included in the analysis all lasted one year or more, with most lasting one to two years. One study comparing Xenical to placebo followed patients for four years.

All the study participants were obese, with average weights in the studies ranging between 192 pounds to 231 pounds.

Sixteen of the trials compared Xenical to placebo, 10 did the same with Meridia, and four followed patients taking Acomplia.

Xenical use was associated with a 6-pound average weight loss over the course of the studies, while Meridia users lost an average of 9 pounds, and Acomplia users lost 10 pounds.

Use of Xenical was associated with improvements in total cholesterol, blood pressure, and blood sugar control in patients with diabetes, but 15% to 30% of participants in most of the Xenical studies complained of gastrointestinal problems including fecal urgency and gas with oily discharge.

Use of Meridia was associated with slight increases in blood pressure in seven studies.

And Acomplia use was associated with a 3% increase in the likelihood of developing a psychiatric problem such as depression, anxiety, and irritability.

While no serious safety issues emerged during the trials, Padwal says there is little information about the safety of using the drugs for many years.

The analysis is published in the latest online issue of the journal BMJ.

"Anti-obesity drugs can help people achieve modest weight loss, but they have to be taken indefinitely or the weight will come back," Padwal says. "Patients and their practitioners have to make a bit of a leap of faith if they plan to continue on these medications for several years."