Role of metformin for weight management in patients without type 2 diabetes.

OBJECTIVE: To evaluate the efficacy and safety of metformin for weight management in overweight and obese patients without type 2 diabetes.

DATA SOURCES: Literature was obtained through MEDLINE Ovid (1950-February week 3, 2008), EMBASE (all years), and a bibliographic review of relevant articles. Key words included metformin, obesity, overweight, and weight loss.

STUDY SELECTION/DATA EXTRACTION: All studies published in the English language that evaluated the effects of metformin on weight in obese or overweight individuals were critically analyzed. Relevant articles were selected for inclusion in this review.

DATA SYNTHESIS: Metformin is first-line pharmacotherapy in the treatment of overweight or obese patients with type 2 diabetes, with beneficial effects on weight in this population. Multiple trials have evaluated the effect of metformin on weight and other metabolic parameters in adults and adolescents without diabetes. Five of 12 trials in adults evaluated weight loss as a primary endpoint. Significant weight reduction was found in 4 of these studies; however, the trials were small and of weak design. Weight reduction was significant in 5 of the 6 adolescent trials; similarly, these studies were limited by weak study design and small patient population. Metabolic parameters (blood pressure, waist circumference, cholesterol parameters, insulin/glucose levels) often showed varying results. Metformin was well tolerated; gastrointestinal effects were the most frequently reported adverse effects.

CONCLUSIONS: The weight loss effects of metformin in overweight or obese adults and adolescents without diabetes appear promising; however, trials have been limited by small patient populations and weak design. Metformin may also have a positive effect on metabolic parameters such as waist circumference, fasting insulin and glucose levels, and triglycerides. Further research involving large-scale trials that evaluate weight loss as a primary outcome is necessary to firmly establish the role of metformin in this population.