Efficacy and safety of metformin for treatment of overweight and obesity in adolescents: an updated systematic review and meta-analysis.

OBJECTIVE To assess the efficacy and safety of using metformin in overweight and obese adolescents without related morbidity. METHODS We conducted a systematic review and meta-analysis of randomized clinical trials published until June 2011, comparing metformin to placebo or other interventions. Our primary variables were baseline BMI changes and development of adverse effects. RESULTS Nine studies (498 participants, mean age 14.2 years; mean BMI 36.4 kg/m² met the inclusion criteria. In all but one study, metformin was combined with lifestyle modification and was compared to placebo combined with changes in lifestyle. Analysis showed that metformin reduced mean BMI by 1.42 kg/m² (95% CI -2.18, 0.66), fasting insulin by 9.9 µU/ml (95% CI -13.8, -6.06) and the HOMA index by -1.78 (95% CI -3.32, -0.23). No changes in any other parameter were observed. No statistical differences were found in the rate of adverse events (33% metformin, 32% placebo).The withdrawal rates due to side effects in the metformin and placebo groups were 2.7% and 2.5%, respectively. CONCLUSIONS The available evidence indicates that, in the short term, administration of metformin in addition to lifestyle modification is relatively effective for reducing BMI and hyperinsulinemia among obese adolescents without related morbidity, and displays an acceptable safety pattern. Nevertheless, its long-term impact is unknown.