PURPOSE: To determine whether protein supplementation (PRO) before an acute bout of heavy resistance training (HRT) would influence postexercise resting energy expenditure (REE) and the nonprotein respiratory exchange ratio (RER). HYPOTHESIS: REE would be increased and RER would be decreased up to 48 h after timed PRO and HRT compared with CHO supplementation and HRT. METHODS: Eight resistance-trained subjects (five men and three women) participated in a double-blind two-trial crossover design, where REE and RER were measured (7:00 a.m.) on four consecutive days. On the second day of trial 1, subjects consumed 376 kJ of either PRO (18 g of whey protein, 2 g of carbohydrate, 1.5 g of fat) or CHO (1 g of whey protein, 19 g of carbohydrate, 1 g of fat) 20 min before a single bout of HRT (nine exercises, 4 sets, 70%-75% 1-repetition maximum). REE and RER were measured 24 and 48 h after HRT. During trial 2, the same protocol was followed except subjects consumed the second supplement before HRT. RESULTS: Compared with baseline, REE was elevated significantly in both CHO and PRO at 24 and 48 h after HRT (P < 0.05). At 24 h after HRT, REE in response to PRO was significantly greater compared with CHO (P < 0.05). RER decreased significantly in both CHO and PRO at 24 h after HRT compared with baseline (P < 0.05). No differences were observed in total energy intake, macronutrient intake, or HRT volume (P > 0.05). CONCLUSIONS: Timing PRO before HRT may be a simple and effective strategy to increase energy expenditure by elevating REE the day after HRT. Increasing REE could facilitate reductions in body fat mass and improve body composition if nutritional intake is stable.