Does metformin help with weight loss?

Metformin does help with weight loss, but the effect is modest and depends strongly on your starting situation. In an observational study of 154 people with overweight or obesity, participants who received metformin lost an average of 5.8 kg over six months, while the untreated group gained an average of 0.8 kg. People with severe insulin resistance benefited the most.

The large Diabetes Prevention Program, with more than 3,200 participants, confirms that metformin produces weight loss, but also shows that an intensive lifestyle programme (aimed at 7% weight loss) is considerably more effective. Metformin is therefore not a substitute for exercise and healthy eating. One notable finding: after ten years of follow-up, the weight loss in the metformin group turned out to be more stable than in the lifestyle group, which initially lost more but subsequently regained some of it.

How metformin influences weight has been reasonably well studied. The drug raises the blood level of a hormone that suppresses appetite via the brainstem. More than 60% of the weight effect is thought to work through this mechanism, as shown by both animal studies and two smaller clinical studies in humans. Other possible pathways, such as influencing gut bacteria or appetite centres in the brain, have not yet been well established and remain hypotheses for the time being.

Metformin is not equally suitable or equally effective for everyone. People with insulin resistance appear to benefit more. In women with PCOS (a hormonal condition involving irregular cycles and elevated male hormones), metformin is sometimes combined with other agents for weight management, but the results of this are mixed. Metformin is not a standard weight-loss drug and in the Netherlands is available by prescription only, so discuss it with your doctor if you think you might benefit from it.