Voluntary running decreases nonexercise activity in lean and diet-induced obese mice.

Abstract Purpose Determine whether voluntary wheel running triggers compensatory changes in nonexercise activity in lean and high-fat diet fed mice. Methods C57Bl/6 mice received a control (C) or a high-fat diet (H) and half of them had free access to a running wheel 5 days/week (CE and HE, respectively) for 10 weeks. Energy intake, nonexercise activity (global activity, distance covered and average speed of displacement in the home cage) and energy expenditure (EE) were evaluated at weeks 5 and 10 during the 2 days without the wheels. Results High-fat diet increased weight gain in H (110%) and HE (60%) groups compared to C and CE groups, respectively, with no effect of exercise. Wheel running increased energy intake (26% CE, 11% HE in week 5; 7% CE, 45% HE in week 10) and decreased distance covered (26% for both CE and HE in week 5; 35% CE and 13% HE in week 10) and average speed (35% CE and 13% HE in week 5; 45% CE and 18% HE in week 10) compared to the respective nonexercised groups. In week 10 there was an interaction between diet and exercise for global activity, which was reduced nearly 18% in CE, H, and HE groups compared to C. Access to a running wheel increased EE in week 5 (11% CE and 16% HE) but not in week 10, which is consistent with the period of highest running (number of turns: weeks 1–5 nearly 100% > weeks 6–10 for CE and HE groups). EE was reduced in H (19%) and HE (12%) groups compared to C and CE, in week 10. Conclusion Voluntary running causes a compensatory decrease in nonexercise activity and an increase in energy intake, both contributing to the lack of effect of exercise on body mass.