Effects of exercise and of food restriction on the development of spontaneous obesity in rats.

The effects of exercise and of food restriction on Zucker obese and lean rats were studied. Zucker obese rats pair-fed to lean littermates gained more body fat on the same intake indicating greater efficiency of diet utilization. Exercise significantly reduced the fat pad weights and body fat content of obese rats. Serum insulin levels were higher in the obese rats and were not influenced by exercise. Exercise had no effect on adipose cellularity of the obese rats. Liver tissue in vitro lipogenic capacity and lipogenic enzyme activities were significantly elevated in obese rats. Exercise increased liver tissue hexokinase and in vitro lipogenesis in lean rats. Exercise increased pentose phosphate pathway enzymes in adipose tissue from lean rats only. Although exercise reduced fat content significantly, obese rats were still fatter (27.7% fat) than the lean controls (6.4% fat). The protein content of obese rats was significantly increased by exercise, indicating that physical activity is important in the regulation of protein metabolism.