BACKGROUND: Green tea (epigallocatechin gallate + caffeine) and protein each were shown to improve body weight maintenance after weight loss. OBJECTIVE: We investigated the effect of a green tea-caffeine mixture added to a high-protein (HP) diet on weight maintenance (WM) after body weight loss in moderately obese subjects. DESIGN: A randomized, placebo-controlled, double-blind parallel trial in 80 overweight and moderately obese subjects [age (mean +/- SD): 44 +/- 2 y; body mass index (BMI; in kg/m(2)): 29.6 +/- 2.0] matched for sex, age, BMI, height, body mass, and with a habitually low caffeine intake. A very-low-energy diet intervention during 4 wk was followed by 3 mo of WM; during the WM period, the subjects received a green tea-caffeine mixture (270 mg epigallocatechin gallate + 150 mg caffeine/d) or placebo, both in addition to an adequate protein (AP) diet (50-60 g protein/d) or a HP diet (100-120 g protein/d). RESULTS: Subjects lost 7.0 +/- 1.6 kg, or 8.2 +/- 2.0%, body weight (P < 0.001). During the WM phase, WM, resting energy expenditure (REE), and fat-free mass (FFM) were relatively increased in both the HP groups and in the AP + green tea-caffeine mixture group (P < 0.05), whereas respiratory quotient and body fat mass were reduced, all compared with the AP + placebo group. Satiety was only increased in both HP groups (P < 0.05). The green tea-caffeine mixture was only effective with the AP diet. CONCLUSION: Green tea-caffeine mixture, as well as an HP diet improved WM independently through thermogenesis, fat oxidation, sparing FFM, and, for the HP diet, satiety; a possible synergistic effect failed to appear.