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 inta ke 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 give n 6 consecutive days of moderate intensity training (3 x 15 minutes per day ). Exercise and postexercise periods were compared with results from the pr etraining period. During swimming, a body weight loss and a decrease in bot h caloric intake and fat selection were observed. This effect was more mark ed in older groups compared to 4 month-old groups. An increase in protein i ntake was observed in females, specially in older groups, whereas no effect was seen in males. The ability to increase caloric ingestion and regain we ight during the postexercise period decreased with advancing age and was be tter 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 inta ke, whereas females significantly increased it. The present findings sugges t a decrease of capacity of adjusting feeding behavior to metabolic needs i n aged rats, may be due to a deterioration of the central control of food i ntake. (C) 2000 Elsevier Science Inc. All rights reserved.