The Effects of Time Restricted Feeding and Exercise on Performance and Body Composition in Healthy Mice

Abstract

Intermittent fasting refers to a period of unregulated caloric consumption paired with a period of complete, or heavily restricted, caloric consumption. One version of this involves splitting the day into a consumption period and a restricted period, known as time‐restricted feeding (TRF). TRF is shown to improve metabolic health and positively affect mitochondria, independent of weight loss. Aerobic exercise is also shown to improve these parameters; however, the combination of intermittent fasting and aerobic exercise in a healthy system has not been examined. The purpose of this study was to examine the effects of the feeding window time in relation to exercise on body weight, body fat percentage, lean mass, and run to exhaustion. Healthy, young mice were placed in one of three groups: ad libitum control group (CON), 18‐hour fasting with a 6‐hour feeding starting immediately post exercise (IM), and 18‐hour fasting with a 6 hour feeding starting 5 hours post exercise (DG). The mice ran 5 days a week, 1 hour a day, for a total of 8 weeks at the beginning of the dark cycle. A run to exhaustion (RTE) was conducted at week 0 and week 8 of the study. Mice were weighed twice weekly and underwent an MRI once a week. Data are presented as mean ± SD. A repeated measures two‐way ANOVA was used to compare groups across time. Significance was set a p< 0.05. There were no significant differences between RTE times at week 0 (p= 0.52). There was a main effect of training across all groups in RTE (p=0.04) with a 14±43% increase in RTE in the CON, 13±33% increase in IM, and 55±86% increase in DG. There was a significant increase in body fat in the DG compared to CON at week 2 (CON 7.1±4.5% DG 13.4±2.3%, p=0.002), week 3 (CON 7.2±4.8% DG 11.6±2.6, p=0.02), and week 4 (CON 7.0±4.5% DG 11.6±1.9%, p=0.006); however, there was no difference between groups at week 8. There was a significant effect of time on body weight and lean mass, demonstrating normal growth (p<0.0001). TRF did not have a significant effect (p=0.24) on body weight, however there was a significant decrease in lean mass in TRF groups at week 8 (CON 24.7±2.2g, IM 22.8±2.1g, DG 22.7±1.8g, p=0.03). Although there was a small decrease in lean mass, TRF did not lead to a change in performance as measured by RTE and timing of fasting did not impact either RTE or body composition. This suggests that performance may not be substantially impacted in individuals using TRF, regardless of the timing of the feeding window.Support or Funding InformationFunded by the University of Memphis School of Health Studies