Exercise training decreases body fat more in self-selecting than in chow-fed rats

This study was designed to examine the influence of exercise training on body weight gain and feeding pattern in rats placed on a self-selection or a chow diet regimen. Adult, male, Wistar rats were submitted to daily 2-h treadmill exercise for 28 days (about 50% of VO2 max) at the beginning of the nocturnal period. Two other groups of rats were examined during the same time: a sedentary group that was deprived of food and water during the training session and a control group without any treatment. Food intakes were continuously recorded. For both feeding regimens, trained rats, relative to their respective controls, showed at the end of the experiment a reduction in body weight gain due to a reduced body fat deposit. Moreover, white adipose tissue (WAT) mass of self-selecting rats was smaller than in chow-fed rats. Exercise training decreased plasma glucose level in chow-fed rats and plasma insulin level in self-selecting rats. In self-selecting rats, food intake was slightly increased due to enhanced protein intake during the nocturnal period and fat intake increased both during the nighttime and daytime periods, whereas in chow-fed rats, food intake was decreased during the daytime period. These results show that, in rats placed on a self-selection regimen, exercise training increased fat consumption but reduced WAT. This could be a consequence of an increased lipolytic capacity of adipocytes in self-selecting trained rats. Thus, it appears from these results that the diet's carbohydrate-to-fat ratio can be an important parameter in shaping the interaction between exercise and body weight.