The management of obesity and overweight revolves around lifestyle changes. However, medication can also play a role in controlling this condition. In this article, we delve into the current evidence surrounding the use of metformin for treating insulin resistance and promoting weight loss.
Weight Loss
The DPP, conducted from 1996 to 2001, is a landmark clinical trial that aimed to assess interventions for preventing or delaying the onset of type 2 diabetes in individuals with prediabetes. The study compared three groups: one implementing lifestyle changes, another receiving metformin treatment, and a placebo control group. The results revealed that lifestyle interventions, involving regular 150 minutes of weekly physical activity and a low-calorie, low-fat diet, were highly effective in reducing the incidence of diabetes. Specifically, the lifestyle intervention group exhibited a remarkable 58% reduction in the risk of developing diabetes compared to the placebo group. The metformin group also showed a significant reduction in diabetes incidence (31%) compared to the placebo group, albeit to a lesser extent than the lifestyle intervention group. These findings underscored the importance of lifestyle modifications as the primary approach to preventing diabetes. After one year, a significant proportion of participants in the lifestyle intervention group (62.6%) and, to a lesser extent, in the metformin group (28.5%) had lost at least 5% of their weight, compared to only 13.4% in the placebo group.
In the DPP, the metformin group lost, on average, 2 kg in the first year. In a more recent study in 2013, high doses of metformin resulted in an average of 5 kg in 6 months among 154 patients with a body mass index ≥27 kg/m2 in an outpatient setting. There was a large variation in the weight outcomes from a weight loss of 335 kg in one patient and a weight gain of 13 kg in another. A meta-analysis of 21 trials (total participants is 1004) showed that metformin has a modest reduction in the BMI of almost one point. The reduction was most significant in participants with obesity and did not continue to decrease after treatment of more than 6 months.
Long-term Weight Loss Maintenance
The DPPOS served as an extension of the DPP study, focusing on evaluating the long-term effects of the initial interventions on diabetes development and related health outcomes. This extended study followed the participants for an additional 15 years. After an average of 10 years of follow-up, intensive lifestyle changes aimed at modest weight loss, reduced the rate of developing type 2 diabetes by 34% and delayed its onset by about 4 years. Additionally, the findings after 10 years demonstrated that metformin treatment reduced the rate of diabetes development by 18% and delayed its onset by 2 years. Approximately 6.2% of the metformin group maintained their weight loss between 6 and 15 years, as compared to 3.7% in the lifestyle group and 2.8% in the placebo group. Predictors of long-term weight loss included greater weight loss in the first year in all groups, older age and continued metformin use in the metformin group, older age, and absence of either diabetes or a family history of diabetes in the lifestyle group.
Conclusion
Metformin is a drug to prevent diabetes and not a weight loss drug. It is not even included in the guidelines for the treatment of obesity. Lifestyle changes remain the cornerstone for weight loss. Metformin has a very modest effect on weight loss in the first 6 months. However, it was superior to lifestyle changes in maintaining weight loss in the long term. If you decide to take metformin after a discussion with your healthcare professional, remember it must be long-term to decrease the incidence of diabetes and maintain weight loss.
References
Diabetes Prevention Program Research Group, 2012. Long-term safety, tolerability, and weight loss associated with metformin in the Diabetes Prevention Program Outcomes Study. Diabetes care, 35(4), pp.731-737.
Seifarth, C., Schehler, B. and Schneider, H.J., 2012. Effectiveness of metformin on weight loss in non-diabetic individuals with obesity. Experimental and clinical endocrinology & diabetes, pp.27-31.
Apolzan, J.W., Venditti, E.M., Edelstein, S.L., Knowler, W.C., Dabelea, D., Boyko, E.J., Pi-Sunyer, X., Kalyani, R.R., Franks, P.W., Srikanthan, P. and Gadde, K.M., 2019. Long-term weight loss with metformin or lifestyle intervention in the diabetes prevention program outcomes study. Annals of internal medicine, 170(10), pp.682-690.
Pu, R., Shi, D., Gan, T., Ren, X., Ba, Y., Huo, Y., Bai, Y., Zheng, T. and Cheng, N., 2020. Effects of metformin in obesity treatment in different populations: a meta-analysis. Therapeutic advances in endocrinology and metabolism, 11, p.2042018820926000.
