Respiratory quotient and energy expenditure after consumption of low vs. high carbohydrate meals

Abstract

Macronutrient consumption influences respiratory quotient (RQ) and energy expenditure (EE) in vivo. EE may be higher after LC than high carbohydrate (HC) meals which may confer a metabolic advantage that contributes to greater weight loss. We used a randomized crossover trial to test the hypothesis that LC meals result in higher postprandial EE and lower RQ than HC meals. Eight healthy, normal weight adults consumed a run‐in diet for 3 days and were admitted into the Clinical Research Center on the 4th day. Resting EE was measured for 45 minutes by indirect calorimetry, then subjects ate a HC or LC meal and postprandial EE was measured for 45 minutes every hour for 4 hr. A 2nd meal of the same composition was consumed and postprandial EE was measured for an additional 4 hr. This procedure was repeated after a >3 day washout period when subjects ate meals of the alternate diet. Postprandial AUC was calculated for EE, RQ, CO2 production (VCO2) and oxygen consumption (VO2) after the entire 9 hr period. Differences between diets in AUC for each variable were measured by one‐tailed paired t‐tests. After consumption of the LC meals, AUC of VO2 was not different but AUC of VCO2 was lower (2.17±1.94 vs 2.04±1.50, p<0.01) resulting in a lower AUC of RQ (4.10±0.63 vs 4.65±0.58; p<0.01). There was no difference in AUC EE over the 9 hr studied; however, the patterns of change of EE suggest that there may be differences if studied for longer periods of time.