Suppression of physical activity and non‐resting energy expenditure during calorie restriction: role in individual differences in adaptive thermogenesis (1101.8)

Abstract

Weight loss requires negative energy balance, which can induce adaptive thermogenesis‐the reduction of energy expenditure (EE) beyond that accounted for by the weight lost. Adaptive thermogenesis varies between individuals. Here, we measured EE and physical activity (PA) before and after 21 days of 50% calorie restriction (CR) in female rats with lean and obesity‐prone phenotypes‐rats strains selectively bred for high and low intrinsic aerobic capacity (HCR and LCR, respectively). Use of female rats minimized potentially confounding effects of group differences in body size. We found that CR decreased EE more than was predicted by loss of weight and lean mass, demonstrating adaptive thermogenesis. Both groups showed similar suppression in resting EE (HCR, 39%; LCR, 34%). The CR‐induced suppression in non‐resting EE, which includes activity EE, was significantly greater in HCR (37%) than in LCR (24%). CR also significantly suppressed PA in HCR but not LCR, but PA was still higher in HCR than in LCR even after CR. Weight loss did not differ between groups. These results suggest that individual differences in CR‐induced adaptive thermogenesis may be accounted for by variation in aerobic capacity. Moreover, it is likely activity EE, not resting or basal metabolism, accounts for individual variation in adaptive thermogenesis.Grant Funding Source: Supported by NIH R01NS055859 and NIH R15DK097644 to CMN