BACKGROUND:

Metformin has been proffered as a therapy for adolescent obesity, although long-term controlled studies have not been reported.

OBJECTIVE:

To test the hypothesis that 48 weeks of daily metformin hydrochloride extended release (XR) therapy will reduce body mass index (BMI) in obese adolescents, as compared with placebo.

DESIGN:

Multicenter, randomized, double-blind, placebo-controlled clinical trial.

SETTING:

The 6 centers of the Glaser Pediatric Research Network from October 2003 to August 2007.

PARTICIPANTS:

Obese (BMI > or = 95th percentile) adolescents (aged 13-18 years) were randomly assigned to the intervention (n = 39) or placebo groups. Intervention Following a 1-month run-in period, subjects following a lifestyle intervention program were randomized 1:1 to 48 weeks' treatment with metformin hydrochloride XR, 2000 mg once daily, or an identical placebo. Subjects were monitored for an additional 48 weeks. Main Outcome Measure Change in BMI, adjusted for site, sex, race, ethnicity, and age and metformin vs placebo.

RESULTS:

After 48 weeks, mean (SE) adjusted BMI increased 0.2 (0.5) in the placebo group and decreased 0.9 (0.5) in the metformin XR group (P = .03). This difference persisted for 12 to 24 weeks after cessation of treatment. No significant effects of metformin on body composition, abdominal fat, or insulin indices were observed.

CONCLUSION:

Metformin XR caused a small but statistically significant decrease in BMI when added to a lifestyle intervention program.

TRIAL REGISTRATION:

clinicaltrials.gov Identifiers: NCT00209482 and NCT00120146.