Resting metabolic rate in bodybuilding: Differences between indirect calorimetry and predictive equations

Estimating resting metabolic rate (RMR) is one of the main determinants of an athlete's energy needs. This study aimed to investigate the RMR of bodybuilding athletes using indirect calorimetry (IC) and compare it with predictive formulas proposed in the scientific literature.

71 volunteers divided into four experimental groups: active control group for women (CGW; n = 16); active control group for men (CGM; n = 17); bodybuilder women (BBW; n = 13); and bodybuilder men (BBM; n = 25) were evaluated. The body composition was performed using the bioelectrical impedance (BIA), and the RMR was measured using an IC. The data obtained from the BIA instrument were used to calculate the RMR of all volunteers using six equations. Data normality was tested, and the unpaired t-test compared anthropometric parameters, body composition, and RMR. The Bland-Altman (B&A) plot was used to analyze the agreement between IC, BIA, and predictive equations, and the difference between the methods was calculated. An analysis of covariance (ANCOVA) with Bonferroni post hoc was used for RMR analysis and adjusted for body weight and skeletal muscle mass.

The main findings indicated that the Johnstone equation showed a large discrepancy underestimating the RMR of BBW and BBM when compared to IC, and the De Lorenzo and Tinsley equations (a) approached the more accurate analysis method of measuring RMR in BBW and BBM, respectively.

Professionals who work with bodybuilding and performance will be able to use the present study to improve their nutrition support.