Funabashi, D.; Dobashi, S.; Sameshima, K.; Sagayama, H.; Nishijima, T.; Matsui, T.

Exercise benefits the body and mind, but its weight loss effect is less than generally expected. Although this phenomenon is likely due to a decrease in non-exercise physical activity (NEPA) and thermogenesis following exercise, the underlying mechanisms and effects of exercise intensity remain unknown. Here we show the potential role of corticosterone dynamics in the decline in NEPA and thermogenesis following vigorous exercise. 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 body temperature (BT) were monitored for two days before and three days after exercise. The daily synchrony between the NEPA and BT was evaluated using a cross-correlation function. Plasma corticosterone was also detected at 6 and 24 h after exercise. Notably, only the vigorous exercise group exhibited a decline in both NEPA and BT, and increased body weight compared to the sedentary group, despite no observed changes in food intake. Furthermore, a distinct negative time lag was identified between the daily dynamics of NEPA and BT following vigorous exercise. A positive correlation was observed between plasma corticosterone levels and changes in NEPA before and after exercise across all exercise groups. Our findings provide evidence for vigorous exercise-specific reduction in NEPA, BT, and their synchrony, likely due to the disturbed circadian rhythm of corticosterone. Declined BT could imply lowered thermogenesis, providing novel insights into the role of exercise intensity in influencing the weight loss effects of exercise.