Age-related changes in adaptive macronutrient intake in swimming male and female Lou rats.

To evaluate the age-related changes in capacity to adjust the nutrient intake to needs, self-selecting male and female Lou/C/jall rats of 4, 6, 12, 16 and 23 months of age were submitted to a swimming exercise. They were given 6 consecutive days of moderate intensity training (3 x 15 minutes per day). Exercise and postexercise periods were compared with results from the pretraining period. During swimming, a body weight loss and a decrease in both caloric intake and fat selection were observed. This effect was more marked in older groups compared to 4 month-old groups. An increase in protein intake was observed in females, specially in older groups, whereas no effect was seen in males. The ability to increase caloric ingestion and regain weight during the postexercise period decreased with advancing age and was better in females than in males. We also showed an age-related effect on the recovery of initial nutrient intake rate that was more pronounced and more precocious for males. Moreover, males tended to decrease their protein intake, whereas females significantly increased it. The present findings suggest a decrease of capacity of adjusting feeding behavior to metabolic needs in aged rats, may be due to a deterioration of the central control of food intake.