The impact of metformin with or without lifestyle modification versus placebo on polycystic ovary syndrome: a systematic review and meta-analysis of randomized controlled trials

Objective: Available evidence has shown that metformin improves insulin sensitivity and weight management in polycystic ovary syndrome (PCOS). Nevertheless, key knowledge gaps remain regarding its efficacy and the specific outcomes in this population. This review evaluates the effectiveness of metformin and lifestyle modification compared with placebo in the management of PCOS and will inform the forthcoming, 2023 evidence-based PCOS guidelines. Design: Systematic review and meta-analysis of the literature. Methods: A search was performed in MEDLINE, EMBASE, PsycINFO, All EBM, and CINAHL. The review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and included randomized controlled trials published in English through July 2022. Results: Moderate certainty of evidence showed a larger reduction of body mass index (BMI) (mean difference [MD] -0.53, 95% confidence interval [CI] -0.95 to -0.12 kg/m(2)), homeostatic model assessment for insulin resistance (MD -0.50, 95% CI -0.91 to -0.09) (critical outcomes), and fasting glucose (MD -0.13, 95% CI -0.19 to -0.07 mmol/L) with metformin compared to placebo with increased mild gastrointestinal adverse effects (odds ratio [OR] 7.67, 95% CI 2.74-21.46). Low certainty of evidence showed a larger reduction of waist-hip ratio (MD -0.02, 95% CI -0.03 to -0.00), total cholesterol (MD -0.24, 95% CI - 0.43 to -0.05 mmol/ L), lowdensity lipoprotein (MD -0.16, 95% CI -0.30 to -0.01 mmol/L), and triglycerides (MD -0.11, 95% CI - 0.20 to -0.02 mmol/L) with metformin than placebo. Conclusions: Metformin should be considered an efficacious adjunct to lifestyle interventions in adults with PCOS, especially for those with a higher BMI, to improve weight loss, insulin resistance, and lipids.