Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic map

Fat-free mass (FFM) is the major predictor of resting metabolic rate (RMR). As protein supplementation during resistance training may augment gains in FFM, we investigated the effects of resistance training combined with protein supplementation on RMR and whether RMR responses could be estimated by a dual-energy X-ray absorptiometry (DXA) metabolic map.Subjects/methods:Healthy adults completed a whole-body periodized resistance training program consisting of 96 workouts (∼9 months). Participants were randomly assigned to supplement with whey protein (whey; n=18), soy protein (soy; n=21) or carbohydrate (carb; n=22). RMR was measured using indirect calorimetry (RMR _IC) and estimated by DXA metabolic mapping (RMR _MM) pretraining and posttraining.Results:RMR_IC increased from pretraining to posttraining in the whole cohort (1653±302 to 1726±291 kcal/day, P=0.001) without differences between the groups. Delta RMR_IC and RMR_MM (73±158 vs 52±41 kcal/day were not significantly different by t-test (P=0.303), although they were not significantly correlated (r=0.081; P=0.535). Stepwise regression identified 43% of the shared variance in delta RMR_IC using total serum thyroxine, RMR_IC and FFM at baseline (P=0.009).Conclusions:These results indicate that 9 months of resistance training significantly increased RMR ∼5% on average, but there was wide variability between individuals, which can be partially accounted for by changes in FFM and thyroid hormones.