Abstract
PURPOSE: Exercise benefits the body and mind, but its weight loss effect is less than generally expected. Although this phenomenon is likely due to an exercise intensity-dependent decrease in non-exercise physical activity (NEPA), resulting in a decrease in non-exercise activity thermogenesis, the underlying mechanisms and effects of exercise intensity remain unknown. Here we show that acute vigorous exercise decreases subsequent NEPA and body temperature (BT) in association with body weight gain. METHODS: Adult male C57BL/6J mice were categorized into three groups: sedentary, moderate exercise, and vigorous exercise, with exercise groups undergoing a 30-min treadmill session. Using an intraperitoneally implanted activity monitor, NEPA and BT were monitored for 2 d before and 3 d after exercise. The daily synchrony between NEPA and BT was evaluated using a cross-correlation function. Plasma corticosterone was also detected 6 and 24 h after exercise. RESULTS: Notably, only the vigorous exercise group exhibited a decline in both NEPA and BT, resulting in body weight gain the following day, despite no observed changes in food intake. Furthermore, vigorous exercise induces a distinct delay in the daily dynamics of NEPA compared with BT. A positive correlation was observed between plasma corticosterone levels and changes in NEPA levels before and after exercise across all exercise groups. CONCLUSIONS: Our findings provide evidence for vigorous exercise-specific reduction in subsequent NEPA, BT, and their synchrony linked to weight gain, likely due to the disturbed circadian rhythm of corticosterone. This is an initial investigation redefining the significance of exercise intensity in beneficial effects beyond the energy expenditure of the exercise itself.