Resistance Training Influences on Resting Metabolic Rate in Men and Women

Obesity is becoming more prevalent in the United States and is a result of a several of factors, including an individual's genetics, environment, and societal influences. Of the most important, however, when managing weight is the balance between energy expenditure and energy intake. One's total energy expenditure is constituted of four main components: resting metabolic rate (RMR), thermic effect of food, non-exercise thermogenesis, and exercise thermogenesis. The most prominent of these is RMR, which accounts for about 60-70% of an individual's total energy expenditure.

Differences in RMR amongst individuals is dependent on a multitude of variables including height, adiposity, age, body mass, training status, and of most importance, fat-free mass (FFM). Research shows that the greater the body size, the greater the RMR. This positive association between height and body mass with RMR is attributed to more massive organ systems needed in order to meet the greater metabolic demands of a bigger individual. Research also supports that age is negatively associated with RMR. This is mostly due to sarcopenia, or the loss of muscle mass. The most important determinant of RMR, however, is FFM. Unlike body mass, FFM only accounts for metabolically active tissues including muscle, bone, blood, and all organs. Fat-free mass has been reported to account for up to 80% of the variance in RMR. Resistance training is shown to increase FFM, which results in increases in RMR. However, there are several elements to a successful, progressive resistance training protocols that result in increases in muscular strength and hypertrophy. Strength and hypertrophy gains result in a greater oxidative capacity of muscle, and consequentially a greater RMR. The most influential factor in muscular strength and hypertrophic resistance training is intensity. Moderate intensity programs are recommended for the nonathletic adult population for safety purposes. An intensity 4 of about 80% 1 RM is appropriate for increases in FFM. Training protocols lasting at least three months and that incorporate whole-body exercises have the greatest effects on FFM and RMR. Most studies show that increases in FFM of 1-2 kg are necessary increase RMR by about 3-8%. Interestingly, RT can produce similar increases in RMR and FFM in obese and overweight populations in leaner individuals. Implementing resistance training has been shown to be an effective method in managing weight and increasing both RMR and FFM.