Comparison 1. Primary outcomes.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Weight loss ‐ (non) caffeine matched interventions	14	1562	Mean Difference (IV, Random, 95% CI)	‐0.95 [‐1.75, ‐0.15]
1.1 Caffeine matched in intervention and control	11	1274	Mean Difference (IV, Random, 95% CI)	‐1.11 [‐1.99, ‐0.24]
1.2 Caffeine in intervention only	3	288	Mean Difference (IV, Random, 95% CI)	‐0.10 [‐0.80, 0.60]
2 Weight loss ‐ studies conducted in/outside Japan	14	1562	Mean Difference (IV, Random, 95% CI)	‐0.95 [‐1.75, ‐0.15]
2.1 Studies conducted in Japan	8	1030	Mean Difference (IV, Random, 95% CI)	‐1.44 [‐2.38, ‐0.51]
2.2 Studies conducted outside Japan	6	532	Mean Difference (IV, Random, 95% CI)	‐0.04 [‐0.50, 0.43]
3 Weight maintenance	2	184	Mean Difference (IV, Random, 95% CI)	‐0.52 [‐2.62, 1.59]
4 Weight loss ‐ BMI	12	1252	Mean Difference (IV, Random, 95% CI)	‐0.47 [‐0.77, ‐0.17]
4.1 Studies conducted in Japan	8	1030	Mean Difference (IV, Random, 95% CI)	‐0.55 [‐0.89, ‐0.20]
4.2 Studies conducted outside Japan	4	222	Mean Difference (IV, Random, 95% CI)	‐0.19 [‐0.48, 0.11]
5 Weight maintenance ‐ BMI	2	184	Mean Difference (IV, Random, 95% CI)	‐0.14 [‐0.78, 0.50]
6 Weight loss ‐ waist circumference	13	1434	Mean Difference (IV, Random, 95% CI)	‐0.99 [‐1.76, ‐0.22]
6.1 Studies conducted in Japan	8	1030	Mean Difference (IV, Random, 95% CI)	‐1.38 [‐2.30, ‐0.46]
6.2 Studies conducted outside Japan	5	404	Mean Difference (IV, Random, 95% CI)	‐0.23 [‐1.39, 0.94]
7 Weight maintenance ‐ waist circumference	2	184	Mean Difference (IV, Random, 95% CI)	‐0.75 [‐2.66, 1.15]
8 Weight loss ‐ waist‐to‐hip ratio	4	339	Mean Difference (IV, Random, 95% CI)	‐0.00 [‐0.02, 0.01]
8.1 Studies conducted in Japan	1	195	Mean Difference (IV, Random, 95% CI)	‐0.01 [‐0.02, ‐0.00]
8.2 Studies conducted outside Japan	3	144	Mean Difference (IV, Random, 95% CI)	0.00 [‐0.02, 0.02]