The effect of metformin on fat distribution and the metabolic syndrome in women with polycystic ovary syndrome—a randomised, double-blind, placebo-controlled trial


Dr J Lord, Department of Obstetrics and Gynaecology, Royal Cornwall Hospital, Truro, Cornwall TR1 3LJ, UK. Email


Objective  To establish whether metformin has a significant action in reducing visceral fat and improving other metabolic parameters in women with polycystic ovary syndrome (PCOS).

Design  Randomised, double-blind, placebo-controlled trial.

Setting  Reproductive medicine clinic.

Population  Forty women with anovulatory PCOS.

Methods  Participants were randomised into receiving metformin 500 mg three times a day or placebo for 3 months.

Main outcome measures  Fat distribution was measured by computed tomography scan. Secondary outcome measures included serum indices of the metabolic syndrome and evidence of ovulation.

Results  We found no significant differences in any of the measures of fat distribution between the placebo and metformin groups. The metformin group had significantly lower total cholesterol (P= 0.02), low-density lipoprotein cholesterol (P= 0.02) and cholesterol:high-density lipoprotein cholesterol ratio (P= 0.05), but there was no statistically significant treatment effect on androgens, insulin, insulin resistance, triglycerides, ovulation or pregnancy.

Conclusions  Metformin has no clinically significant effect in reducing visceral fat mass, although it does have a beneficial effect on lipids. This trial lends support to the growing evidence that metformin is not a weight loss drug. Metformin might therefore be used as an adjunct to lifestyle modification in women with PCOS, but not as a substitute for it.