Published on 2 May 2019

Researchers find that taking metformin to treat type 2 diabetes may additionally help weight loss.

Weight loss could be an additional beneficial side effect of taking metformin according to a new study.

Researchers from the US and Sweden were looking to identify reliable predictors of long-term weight loss that could lead to improved weight management.

The study, recently published in Annals, compared long-term weight loss in people thought to be at risk of type 2 diabetes who had either been advised to follow a strict diet and exercise plan, been given the diabetes medicine metformin or been given a placebo (pretend) medicine

While metformin is not approved as a weight loss drug it can help the body use insulin to process sugar and is often used as a first treatment for people when newly diagnosed with type 2 diabetes. Weight loss is a known side effect of the treatment.

The results of the study found that people who had initially been put on the diet and exercise plan lost more weight in the first year than those who were given metformin.

However, in 15 years of follow-up those who had lost weight while taking metformin were more likely to maintain their weight loss. In addition many of those on the diet and exercise plan later regained weight.

Researchers concluded: “Among persons with weight loss of at least 5% after 1 year, those originally randomly assigned to metformin had the greatest loss during years 6 to 15. Older age and the amount of weight initially lost were the most consistent predictors of long-term weight loss maintenance.”

While the study is the first to show very long-term effects of any medicine on weight loss, an NHS Behind the Headlines report of the study added a note of caution: “The study has limitations that we should be aware of: this is a secondary analysis that looked at just one small section of people from the original randomised trial, which makes it more prone to bias than the original trial results; it did not look at other possible predictors of long-term weight loss, such as genetic factors; the long-term results are based only on people who lost at least 5% of their body weight in the first year – so 70% of the people who started the trial were not included.

“While metformin is widely used in diabetes treatment, it is not licensed as a weight loss medicine. For it to become licensed for weight loss, the manufacturers would have to put forward research evidence to show it works and is safe for this use.

“While metformin may have potential as an aid for people needing to maintain weight loss in future, the study reminds us that in the original 1-year trial, the most successful weight-loss treatment was the diet and exercise plan.”

Read the report in Annals
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