Intermittent Fasting Suppresses Activity‐Associated Energy Expenditure and Enhances Weight Loss in Obesity‐Prone Rats

Abstract

Weight and fat loss occur when total energy expenditure (EE) is higher than energy input. This can be achieved by lowering caloric input through altering diet, or by increasing total EE. Activity‐associated EE is suppressed during weight loss and maintenance of reduced weight; this occurs through decreased physical activity levels along with increased fuel economy of activity. These adaptations take time to occur. Both activity‐associated EE and resting EE have been shown to decrease during calorie restriction‐induced weight loss in rats. Recently, attention is being paid to alternatives to calorie‐restriction, such as time‐restricted feeding approaches including intermittent, or alternate‐day, fasting. We have found that, unlike daily calorie‐restriction, intermittent fasting achieves a superior result in obesity‐prone rats compared to their lean counterparts. Here, we investigate the potential contribution of physical activity‐associated EE to the altered energy balance contributing to weight loss during intermittent fasting. We examined female high‐and‐low‐capacity runners (HCR and LCR, respectively), rats artificially selected for high and low intrinsic aerobic capacity. HCR are lean and more physically active than their obesity‐prone LCR counterparts. We induced equivalent weight loss within phenotype using intermittent fasting and daily calorie‐restriction, and measured activity‐associated EE during treadmill walking. Calorie‐restriction and intermittent fasting induced equivalent suppression of activity‐associated EE in both HCR and LCR. As we saw previously, intermittent fasting was significantly more effective in inducing weight loss in the obesity‐prone LCR than in HCR. Interestingly, our data do not support the hypothesis that the enhanced weight loss occurs through a release from adaptive thermogenesis in activity‐associated EE. There was also no difference in activity‐associated EE between fed and fasted days in the intermittent‐fasted rats. This implicates intermittent fasting as a superior means of weight loss in obesity‐prone rats, and suggests that the efficacy of intermittent fasting might also vary between people.Support or Funding InformationFunding: NIH NIDDK R15‐DK‐097644 and R15‐DK‐108668 to Colleen M Novak; P40 OD021331 to Lauren G Koch. Resource for Rat Genetic Models of Aerobic Capacity: P40 OD021331(Lauren G Koch, Principal Investigator; Steven L Britton, Co‐Investigator)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.