NEW YORK (Reuters Health) - Obese adolescents who are put on a low-calorie diet and exercise program do not seem to derive any additional benefit from taking the diet drug sibutramine, sold in the United States under the trade name Meridia, according to a Dutch study.

In previous studies, sibutramine resulted in weight loss and enhanced the effects of a low-calorie diet for up to 2 years in obese adults, note Dr. Edgar G. A. H. Van Mil, of the VU University Medical Center, Amsterdam, and colleagues in the Journal of Clinical Endocrinology and Metabolism.

In adults, sibutramine reduces calorie intake by increasing the feeling of fullness and increasing the metabolic rate, so more calories are burned. But it is unclear if the drug has the same effects on obese adolescents.

The researchers therefore conducted a study with 24 obese teens who were randomly assigned to sibutramine or a placebo. Both groups also where given a low-calorie diet and physical exercise program to follow. After 12 weeks, the teens stayed on their diet and exercise program, but stopped taking the drug.

The weight of the patients was comparable in both groups after the 12-week trial, the researchers report. However, the weight loss concluded after the placebo was discontinued, whereas weight loss only stabilized in teens who discontinued sibutramine.

The team also measured the subjects' body composition and metabolic rate using underwater weighing and special X-ray imaging techniques. The changes in the percentage of fat mass were not different between the sibutramine and placebo groups and there were no significant changes in metabolism, the investigators found.

The researchers then measured basal metabolic rate, the amount of calories the body burns while at rest. They found that it initially decreased in the placebo group and remained constant in the sibutramine group. However, during the follow-up period, the basal metabolic rate increased in the placebo group and decreased in the sibutramine group.

It's possible, the team speculates, that the effect of sibutramine was masked by the effects of diet and exercise.

SOURCE: Journal of Clinical Endocrinology and Metabolism, April 2007.