Influence of a Gas Exchange Correction Procedure on Resting Metabolic Rate and Respiratory Quotient in Humans

Objective: The aim of this study was to determine the influence of a gas exchange correction protocol on resting metabolic rate (RMR) and respiratory quotient (RQ), assessed by a Vmax Encore 29n metabolic cart (SensorMedics Co., Yorba Linda, California) in overnight fasted and fed humans, and to assess the predictive power of body size for corrected and uncorrected RMR. Methods: Healthy participants (23 M/29 F; 34 ± 9 years old; 26.3 ± 3.7 kg/m²) ingested two 3-hour-apart glucose loads (75 g). Indirect calorimetry was conducted before and hourly over a 6-hour period. Immediately after indirect calorimetry assessment, gas exchange was simulated through high-precision mass-flow regulators, which permitted the correction of RMR and RQ values. Results: Uncorrected and corrected RMR and RQ were directly related at each time over the 6-hour period. However, uncorrected versus corrected RMR was 6.9% ± 0.5% higher (128 ± 7 kcal/d; P < 0.0001), while RQ was 14.0 ± 0.4% lower (−0.114 ± 0.003; P < 0.0001) when compared throughout the whole period. Body weight, sex, and age explained a larger fraction of the variance when corrected RMR was considered (adjusted R² = 0.71; P < 0.0001) versus uncorrected RMR (adjusted R² = 0.59; P < 0.0001). Conclusions: Applying a protocol to correct gas exchange in humans over a 6-hour period is feasible and provides information of improved accuracy.