Effects of exercise and of food restriction on adipose tissue cellularity.

The body weight and fat content of young, growing rats were kept low by regularly performed endurance exercise by the rats or by restriction of their food intake over a period of 14 wk. The cellular character of epididymal fat pads was studied to determine if the reduction in fat was due to a decrease in the number of adipose cells, their size, or both. Compared with the sedentary freely eating control animals, both the exercisers and the sedentary paired-weight animals, which had their food intake restricted in order to maintain their body weights approximately the same as those of the exercisers, had significantly lighter epididymal fat pads (P < 0.001). This fat depot in the exercisers contained fewer (4.46 +/- 0.48 x 10(6) vs. 6.89 +/- 0.55 x 10(6) cells/pad; P < 0.001) and smaller (0.286 +/- 0.041 vs. 0.462 +/- 0.040 micro g of lipid/cell; P < 0.001) cells than that in the sedentary freely eating animals. Food restriction also resulted in a significant reduction in adipose tissue cellularity (P < 0.05). Epididymal fat pads from the calorie-restricted rats had an average of 5.72 +/- 0.33 x 10(6) cells and they contained 0.319 +/- 0.024 micro g of lipid/cell. These results demonstrate that exercise in addition to food restriction in early life is effective in reducing the rate of accumulation of cells in epididymal fat pads of rats.