From the Guidelines
Metformin typically results in an average weight loss of 2-3 kg (4.4-6.6 pounds) over the first six months of treatment, as supported by the most recent evidence 1. This weight loss is generally observed in individuals using metformin for diabetes management and can vary significantly between individuals. The standard dosing of metformin begins at 500 mg once or twice daily with meals, potentially increasing to a maximum of 2000-2500 mg daily divided into two or three doses as tolerated. Key factors contributing to weight loss with metformin include:
- Reduced appetite
- Decreased intestinal glucose absorption
- Improved insulin sensitivity, which helps regulate blood sugar without causing the weight gain often associated with other diabetes medications
- Influence on gut bacteria in ways that may support weight management While not FDA-approved specifically for weight loss, metformin is sometimes prescribed off-label for this purpose, particularly for individuals with insulin resistance or prediabetes, as noted in earlier guidelines 1. However, the most recent and highest quality study 1 provides the most relevant information for current clinical practice. Side effects of metformin may include gastrointestinal issues like diarrhea, nausea, and abdominal discomfort, which typically improve over time with continued use or dose adjustments.
From the FDA Drug Label
Mean baseline body weight was 201 lbs and 206 lbs in the metformin hydrochloride tablets and placebo arms, respectively. Mean change in body weight from baseline to week 29 was -1.4 lbs and -2. 4 lbs in the metformin hydrochloride tablets and placebo arms, respectively. Mean baseline body weight was 202 lbs, 203 lbs, and 204 lbs in the metformin hydrochloride tablets /glyburide, glyburide, and metformin hydrochloride tablets arms, respectively. Mean change in body weight from baseline to week 29 was 0.9 lbs, -0.7 lbs, and -8. 4 lbs in the metformin hydrochloride tablets /glyburide, glyburide, and metformin hydrochloride tablets arms, respectively. Mean baseline body weight was 205 lbs and 189 lbs in the metformin hydrochloride tablets and placebo arms, respectively. Mean change in body weight from baseline to week 16 was -3.3 lbs and -2. 0 lbs in the metformin hydrochloride tablets and placebo arms, respectively. The average weight loss on metformin varies across studies, with changes ranging from:
- -1.4 lbs over 29 weeks in one study 2
- -8.4 lbs over 29 weeks in another study 2
- -3.3 lbs over 16 weeks in a pediatric study 2 It is essential to note that these values are not consistent across all studies, and weight loss may vary depending on the specific population and study design.
From the Research
Average Weight Loss on Metformin
- The average weight loss on metformin varies across different studies, with some studies showing a significant reduction in weight and others showing a more modest effect 3, 4, 5.
- A study published in 2022 found that patients with type 2 diabetes who received metformin monotherapy lost an average of 4.5 kg of weight over 12 weeks, which corresponds to a 4.9% reduction in body weight 3.
- Another study published in 2013 found that metformin-treated patients with obesity lost an average of 5.8 kg of weight over 6 months, which corresponds to a 5.6% reduction in body weight 4.
- A retrospective cohort study published in 2021 found that patients with or without type 2 diabetes/prediabetes who received metformin monotherapy lost an average of 6.5 kg of weight over 6 months, which corresponds to a 6.0-6.1% reduction in body weight 5.
- The weight loss effects of metformin may be influenced by factors such as insulin resistance, with some studies suggesting that patients with severe insulin resistance may lose more weight on metformin than those with mild insulin resistance 4.
Comparison with Other Treatments
- Metformin has been compared to other treatments, such as liraglutide and sitagliptin, in terms of its effects on weight loss 3, 6.
- A study published in 2022 found that the combination of liraglutide and metformin resulted in greater weight loss than metformin monotherapy, with an average weight loss of 11.3 kg over 12 weeks 3.
- Another study published in 2011 found that liraglutide was superior to sitagliptin in terms of weight loss, with an average weight loss of 2.78-3.68 kg over 52 weeks 6.
Mechanisms of Weight Loss
- The mechanisms by which metformin induces weight loss are not fully understood, but may involve modulation of hypothalamic appetite regulatory centers, alteration in the gut microbiome, and reversal of consequences of aging 7.
- Metformin may also have effects on glucose and lipid metabolism that contribute to its weight loss effects 3, 4.