The drug metformin is not only a diabetes drug but also can be effective in the battle against antipsychotic drug-induced weight gain.

Atypical antipsychotic (AAP) medications have been used increasingly for the management of patients with a variety of psychotic disorders and severe behavioral disturbances.

But in the past decade, there has been a growing concern among clinicians and researchers that use of AAP medications may be related to potentially serious adverse metabolic effects, including weight gain, hyperlipidemia (high fat levels in the blood), and glucose intolerance.

The said effect was found even better when metformin is combined with lifestyle interventions such as psycho-educational, dietary, and exercise programs.

According to the authors of the said study:

"In this 12-week study, we found statistically significant decreases in mean weight, BMI [body mass index], waist circumference, insulin, and IRI [insulin resistance index] among patients in the lifestyle-plus-metformin, metformin-alone, and lifestyle-plus-placebo groups, but not among those in the placebo-alone group whose measurements continued to increase.

Lifestyle intervention and metformin alone and in combination demonstrated efficacy for antipsychotic-induced weight gain. Lifestyle intervention plus metformin showed the best effect on weight loss. Metformin alone was more effective in weight loss and improving insulin sensitivity than lifestyle intervention alone."

Metformin is more popularly known in the market as Glucophage (a pdf file) - a product of Bristol-Myers Squibb.

Read more details from The JAMA and Archives Journal.