Comparison 2. Metformin versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 drop‐outs (12‐14 weeks)	3	158	Risk Ratio (IV, Random, 95% CI)	1.22 [0.09, 16.35]
2.2 fasting blood glucose (12‐14 weeks)	5	264	Mean Difference (IV, Random, 95% CI)	‐0.19 [‐0.46, 0.08]
2.2.1 Endpoint	3	173	Mean Difference (IV, Random, 95% CI)	‐0.35 [‐0.60, ‐0.11]
2.2.2 Change from baseline	2	91	Mean Difference (IV, Random, 95% CI)	0.01 [‐0.21, 0.22]
2.3 BMI (12‐14 weeks)	5	264	Mean Difference (IV, Random, 95% CI)	‐1.37 [‐2.04, ‐0.70]
2.3.1 Endpoint	3	173	Mean Difference (IV, Random, 95% CI)	‐1.75 [‐2.38, ‐1.12]
2.3.2 Change from baseline	2	91	Mean Difference (IV, Random, 95% CI)	‐1.20 [‐2.17, ‐0.23]
2.4 waist circumference (12‐14 weeks)	4	192	Mean Difference (IV, Random, 95% CI)	‐1.44 [‐2.93, 0.04]
2.4.1 Endpoint	2	101	Mean Difference (IV, Random, 95% CI)	‐0.30 [‐6.26, 5.66]
2.4.2 Change from baseline	2	91	Mean Difference (IV, Random, 95% CI)	‐0.93 [‐1.21, ‐0.64]
2.5 systolic blood pressure (14 weeks)	1	54	Mean Difference (IV, Random, 95% CI)	‐2.50 [‐9.09, 4.09]
2.6 diastolic blood pressure (14 weeks)	1	54	Mean Difference (IV, Random, 95% CI)	1.20 [‐3.55, 5.95]
2.7 total cholesterol (12‐14 weeks)	2	109	Mean Difference (IV, Random, 95% CI)	‐0.34 [‐0.93, 0.26]