Comparison 1. Metformin versus placebo/no‐pharmacological weight gain prevention treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Weight: average endpoint/change in body weight	4	131	Mean Difference (IV, Random, 95% CI)	‐4.03 [‐5.78, ‐2.28]
1.2 Weight: average endpoint/change in body mass index	5	227	Mean Difference (IV, Random, 95% CI)	‐1.63 [‐2.96, ‐0.29]
1.3 Weight: average endpoint/change in waist circumference	4	232	Mean Difference (IV, Random, 95% CI)	‐1.13 [‐4.28, 2.02]
1.4 Leaving the study early: for any reason	4	137	Risk Ratio (M‐H, Random, 95% CI)	1.02 [0.25, 4.13]
1.5 Reports of nausea	2	69	Risk Ratio (M‐H, Random, 95% CI)	2.38 [0.28, 19.95]
1.6 Mental state	2	111	Mean Difference (IV, Random, 95% CI)	0.02 [‐0.63, 0.67]
1.6.1 SANS (higher = worse)	1	37	Mean Difference (IV, Random, 95% CI)	‐0.05 [‐1.38, 1.28]
1.6.2 SAPS (higher = worse)	1	37	Mean Difference (IV, Random, 95% CI)	0.09 [‐0.67, 0.85]
1.6.3 BPRS (higher = worse)	1	37	Mean Difference (IV, Random, 95% CI)	‐1.80 [‐6.50, 2.90]
1.7 Physiological: laboratory measures	4		Mean Difference (IV, Random, 95% CI)	Subtotals only
1.7.1 Fasting blood glucose (mg/dL)	4	195	Mean Difference (IV, Random, 95% CI)	‐10.04 [‐28.27, 8.19]
1.7.2 HDL cholesterol (mg/dL)	2	58	Mean Difference (IV, Random, 95% CI)	2.43 [‐4.07, 8.92]
1.7.3 Insulin (mIU/mL)	2	74	Mean Difference (IV, Random, 95% CI)	‐2.82 [‐9.53, 3.89]
1.7.4 Insulin resistance index	3	93	Mean Difference (IV, Random, 95% CI)	‐0.80 [‐1.62, 0.02]
1.7.5 LDL cholesterol (mg/dL)	2	57	Mean Difference (IV, Random, 95% CI)	‐3.54 [‐39.77, 32.68]
1.7.6 Total cholesterol (mg/dL)	2	57	Mean Difference (IV, Random, 95% CI)	‐6.71 [‐30.35, 16.92]
1.7.7 Triglycerides (mg/dL)	2	59	Mean Difference (IV, Random, 95% CI)	‐17.18 [‐45.31, 10.94]