Figure 8.

Increases in energy expenditure due to early-life Na depletion are primarily the result of increased expenditure during rest. A: total daily locomotion vs. age. d, Day. B: total hours sleeping per day vs. age. C: cartoon illustrating distinct components contributing to total energy expenditure (Total), including both activity-dependent energy expenditure and resting metabolic rate (Resting). Resting metabolic rate comprises basal metabolic rate (Basal), the thermic effect of feeding, and adaptive thermogenesis. D: energy expenditure during rest corrected for fat-free mass (FFM; males 17.67 g, females 15.03 g), fat mass (males 5.27 g, females 3.79 g), and 24-h food intake (males 0.462 kcal/h, females 0.386 kcal/h) by general linear modeling (GLM). E: activity-dependent energy expenditure, calculated as the difference between total daily expenditure and resting expenditure and corrected for FFM, fat, and food intake as in D. F: efficiency of activity-dependent energy expenditure, reflecting the energy invested per unit distance moved, corrected for FFM and fat as in D. For all panels, 0.04% n = 6 males + 8 females vs. 0.30% n = 8 males + 8 females. For A and B, data analyzed by 2-way repeated-measures ANOVA, followed by Šídák's multiple comparisons test. For C and D, data analyzed by GLM. For all panels, data presented as mean or estimated marginal means ± SE. C created with BioRender.