DOES METFORMIN CAUSE WEIGHT LOSS?
Maybe, but the effect is not meaningful
Texas Telemedicine Doctor
August 2025
August 2025
Metformin, a widely prescribed treatment for type 2 diabetes, is promoted as a weight-loss drug by some practices, including many telemedicine companies specializing in weight loss. Metformin is not FDA-approved for weight loss, and until recently, has never been widely prescribed for this purpose. Its blood-sugar-lowering effect in diabetes primarily occurs through inhibition of glycerophosphate dehydrogenase, a mitochondrial enzyme involved in glucose production.
So does metformin cause weight loss? Small, low-quality studies have found that it causes an average decrease in BMI of 0.56, which represents approximately 3.5 lbs in the average adult. [Metformin meta-analysis] One large, high-quality study, often cited by those promoting metformin for weight loss, has been performed. The Diabetes Prevention Program Trial (DPPT), published in 2002, was designed to evaluate the effects of metformin on preventing progression to diabetes among patients with prediabetes; average weight loss was a secondary outcome. DPPT randomized 3,234 adults with prediabetes and an average BMI of 34 and weight of 207 pounds to one of three therapies: Metformin 850 mg twice daily, placebo twice daily, or intensive lifestyle intervention (one-on-one diet and exercise counseling). After a mean follow-up of 2.8 years, the lifestyle intervention group lost 6% of their body weight, the metformin group lost 2.2%, and the placebo group lost 0.1%. Diabetes incidence was 4.8%, 7.8%, and 11%, respectively. Gastrointestinal side effects, including diarrhea, flatulence, and nausea, were common in the metformin group.
DPPT, the largest study to evaluate the effects of metformin on weight loss, found that metformin enhanced weight loss by 2.1% over 2.8 years compared to placebo. This effect size is not meaningful and does not support prescribing metformin for weight loss.
So does metformin cause weight loss? Small, low-quality studies have found that it causes an average decrease in BMI of 0.56, which represents approximately 3.5 lbs in the average adult. [Metformin meta-analysis] One large, high-quality study, often cited by those promoting metformin for weight loss, has been performed. The Diabetes Prevention Program Trial (DPPT), published in 2002, was designed to evaluate the effects of metformin on preventing progression to diabetes among patients with prediabetes; average weight loss was a secondary outcome. DPPT randomized 3,234 adults with prediabetes and an average BMI of 34 and weight of 207 pounds to one of three therapies: Metformin 850 mg twice daily, placebo twice daily, or intensive lifestyle intervention (one-on-one diet and exercise counseling). After a mean follow-up of 2.8 years, the lifestyle intervention group lost 6% of their body weight, the metformin group lost 2.2%, and the placebo group lost 0.1%. Diabetes incidence was 4.8%, 7.8%, and 11%, respectively. Gastrointestinal side effects, including diarrhea, flatulence, and nausea, were common in the metformin group.
DPPT, the largest study to evaluate the effects of metformin on weight loss, found that metformin enhanced weight loss by 2.1% over 2.8 years compared to placebo. This effect size is not meaningful and does not support prescribing metformin for weight loss.
