The University of Tsukuba and Tokyo Metropolitan University reveal through mouse experiments that vigorous exercise causes weight gain — Decreased physical activity and body temperature due to disturbances in circadian rhythm

A research group led by Assistant Professor Takashi Matsui and Researcher Daisuke Funabashi of the Institute of Health and Sport Sciences at the University of Tsukuba and Associate Professor Takeshi Nishijima of the Graduate School of Human Health Sciences at Tokyo Metropolitan University, has announced their animal experiment results showing that vigorous exercise decreases subsequent physical activity and body temperature, causing weight gain. Experiments in mice showed that vigorous exercise increased the levels of stress hormone "corticosterone" and disrupted the circadian rhythm, thereby losing the weight loss effect. The results were published in the June 6 issue of the international journal Medicine & Science in Sports & Exercise.

Although exercise-induced increases in energy expenditure are important for preventing obesity, the weight-loss effect of exercise is often less than expected because total energy expenditure does not increase due to decreases in physical and metabolic activity after exercise. Vigorous exercise involving a large physical load is considered to be accompanied by excessive stress responses, decreasing physical activity and other physiological activity after exercise.

In mice and rats, vigorous exercise promotes the secretion of the stress hormone "corticosterone." Similar to physical activity, corticosterone secretion has a circadian rhythm and is involved in the regulation of physical activity levels. Corticosterone is a steroid hormone secreted by the adrenal cortex of rodents in response to stress load and is known to promote gluconeogenesis. While the circadian rhythm of corticosterone secretion, with trough and peak levels at bedtime and at the time of awakening, respectively, regulates physical and mental activity and supports vigorous exercise, this circadian rhythm is disturbed when physical and mental activity declines because of depression and other causes. As a result of this, vigorous exercise may cause weight gain by decreasing physical activity and thermogenesis after exercise in association with "corticosterone." However, it was unclear what type of exercise would cause the subsequent decreases in physical activity and thermogenesis.

In the present study, mice were divided into three groups: the vigorous exercise, moderate exercise and sedentary groups. The physical activity level and deep body temperature as an index of thermogenesis were measured before and after exercise. These values were measured over time from 2 days before to 3 days after exercise. Moreover, plasma corticosterone levels were assessed at 6-hour post-exercise, which corresponds to the time before the mice awakened, to determine the relationship with physical activity by the exercise intensity. The results showed that the post-exercise physical activity level and deep body temperature decreased only in the vigorous exercise group. Despite no change in food intake, there was an increase in body weight. The synchrony between the physical activity level and body temperature was also disturbed, and a positive correlation was observed: the lower the blood corticosterone level at the time of awakening, the lower the physical activity level.

Matsui said, "This study shows that vigorous exercise decreases subsequent physical activity and thermogenesis, causing weight gain. Traditionally, exercise-related and nonexercise physical activity levels have been evaluated using similar but different experimental equipment and environments. Thus, these are actually difficult to evaluate in an integrated manner and have generally been studied separately. This was also a difficult point in this study, but we could realize simultaneous measurement by combining the 'exercise fatigue model' established by Matsui using mice in which environmental and social factors affecting physical activity can be controlled, and the 'evaluation method for nonexercise physical activity' developed by the first author, Dr. Funabashi. Moving forward, we will focus on the exercise intensity and the mode, quantity and environment. Our ultimate goal is to identify the neural factors that reduce post-exercise physical activity for the development and proposal of biomarkers and lifestyles that predict and prevent post-exercise physical activity decline."

Journal Information
Publication: Medicine & Science in Sports & Exercise
Title: Acute Vigorous Exercise Decreases Subsequent Non-Exercise Physical Activity and Body Temperature Linked to Weight Gain
DOI: 10.1249/MSS.0000000000003487