The obese kids who took the drug, metformin XR, lost a small but statistically significant amount of weight, says a study in the February issue of Archives of Pediatrics & Adolescent Medicine.

According to the study, almost a third of American children are overweight or obese, conditions that put them at high risk for type 2 diabetes and high blood pressure.

While some doctors use metformin to treat non-diabetic fat teens, it hasn't been clear if it actually works.

Researchers enrolled 77 fat adolescents, aged 13 to 18, in a program designed to boost their physical activity and help them control their diet. Some received a placebo, while others got a daily dose of 2,000 milligrams of metformin XR.

Over a year, the average body-mass index -- a measurement of weight in relation to height -- fell by 0.9 in the metformin group but grew by 0.2 in those who took a placebo.

"Metformin was safe and tolerated in this population. These results indicate that metformin may have an important role in the treatment of adolescent obesity," the authors concluded. "Longer-term studies will be needed to define the effects of metformin treatment on obesity-related disease risk in this population."

More information

The U.S. National Library of Medicine has more on metformin.

SOURCE: American Medical Association, Feb. 1, 2010

-- Randy Dotinga