Detraining after short‐term exercise induces hyperphagia and obesity with fatty liver and brown adipose tissue whitening in young male OLETF rats

Abstract This study examined the effects of exercise and detraining at a young age on fat accumulation in various organs. Four‐week‐old male Otsuka Long‐Evans Tokushima Fatty (OLETF) rats were assigned to either the non‐exercise sedentary (OLETF Sed) or exercise groups. The exercise group was subdivided into two groups: exercise between 4 and 12 weeks of age (OLETF Ex) and exercise between 4 and 6 weeks of age followed by non‐exercise between 6 and 12 weeks of age (OLETF DT). Body weight was significantly lower in the OLETF Ex group than in the OLETF Sed group at 12 weeks of age. Fat accumulation in the epididymal white adipose tissue, liver, and brown adipose tissue was suppressed in the OLETF Ex group. During the exercise period, body weight and food intake in the OLETF DT group were significantly lower than those in the OLETF Sed group. However, food intake was significantly higher in the OLETF DT group than in the OLETF Sed group after exercise cessation, resulting in extreme obesity with fatty liver and brown adipose tissue whitening. Detraining after early‐onset exercise promotes hyperphagia, causing extreme obesity. Overeating should be avoided during detraining periods in cases of exercise cessation at a young age.