According to this study:
* Metformin with lifestyle interventions can decrease body mass index (BMI) and waist circumference in patients taking antipsychotic medication.
* Metformin alone is effective for decreasing BMI, waist circumference, fasting glucose levels, and insulin resistance.
Patients who use antipsychotic medication often gain weight. In this 12-week, randomized, double-blind, placebo-controlled study, the authors investigated combinations of lifestyle interventions and medication to decrease body mass index (BMI), waist circumference, insulin levels, and insulin resistance index levels in patients with schizophrenia. All 128 adult study patients in a hospital in China had gained more than 10% of their body weight within a year of starting an antipsychotic medication.
The patients were randomized into four groups of 32 patients each: metformin 750 mg per day, daily placebo, lifestyle intervention with metformin 750 mg per day, and lifestyle intervention with placebo. Lifestyle interventions included exercise, diet, and an educational program about healthful eating and weight management.
Lifestyle intervention with metformin caused significantly greater decreases in weight, BMI, and weight circumference than the other three regimens. Patients in this group decreased their weight by 7.3%, compared with 4.9% in the metformin-only group and 2.2% in the lifestyle-with-placebo group; those in the placebo group increased their weight by 4.8%. Average BMI decreased by 1.8 in the lifestyle-with-metformin group, by 1.2 in the metformin-only group, and by 0.5 in the lifestyle-with-placebo group; mean BMI increased by 1.2 in the placebo group.
Fasting glucose, insulin, and insulin resistance index levels were significantly reduced in the lifestyle-with-metformin, metformin-only, and lifestyle-with-placebo groups.
The authors recommend lifestyle intervention with metformin as first-line treatment, and metformin alone as second-line treatment, in those gaining weight due to antipsychotic medication use.