Effectiveness of Metformin on Weight Loss in Non-Diabetic Individuals with Obesity

Objective: The efficacy of metformin for the treatment of obesity has been evaluated in few clinical trials with inconclusive results. Moreover, the effectiveness in a real-life outpatient setting has not been tested until today. In this study we aimed to examine the effectiveness of metformin as a weight reducing drug in obese and overweight patients with regard to their degree of insulin resistance. Design and patients: We treated 154 consecutive patients with a body mass index >= 27 kg/m(2) in an outpatient setting over 6 months with metformin up to a dosage of 2 500 mg per day. Additionally, we included 45 untreated patients as controls. Patients were monitored for weight changes over 6 months. Before metformin treatment was started insulin sensitivity was determined in all patients by calculating HOMA index and Matsuda index after a 75 g oral glucose tolerance test. Results: The mean weight loss in the metformin treated group was 5.8 +/- 7.0 kg (5.6 +/- 6.5 %). Untreated controls gained 0.8 +/- 3.5 kg (0.8 +/- 3.7 %) on average. Patients with severe insulin resistance lost significantly more weight as compared to insulin sensitive patients. The percentage of weight loss was independent of age, sex or BMI. Conclusion: Metformin is an effective drug to reduce weight in a naturalistic outpatient setting in insulin sensitive and insulin resistant overweight and obese patients.