Fig. 1: Fasting resting energy expenditure, substrate oxidative rates, respiratory quotient, and food quotient on the ground and inflight.

Ground and inflight fasting resting energy expenditure (a), carbohydrate oxidation rate (b), lipid oxidation rate (c), respiratory quotient (RQ, d), and food quotient (FQ, e). Values are interquartile range with median and lsmeans (SE) from mixed-effects models accounting for repeated measurements, with differences (Diff.) presented with their 95% confidence interval. Models for energy expenditure and substrate oxidation rates are adjusted for FFM and FM. *P < 0.05, **P < 0.01, ***P < 0.001. Scatterplot of individual ground (white circles) and inflight (gray squares) fasting RQ with corresponding FQ (f). Illustration of the partial relationship of changes in fasting RQ (difference between inflight fasting RQ and ground fasting RQ) with inflight FQ adjusted for ground RQ using the scatterplot of the relationships of the residual changes in fasting RQ (controlling for ground RQ) with the residual inflight FQ (controlling for ground fasting RQ; g). Least square regression lines are plotted with their 95% confidence interval (gray area). a–d, f: inflight data from 10 subjects; e: ground data from 7 subjects; g data from 10 subjects. FFM fat-free mass, FM fat mass, RQ respiratory quotient, FQ food quotient.