Effects of stopping training on size and response to insulin of fat cells in female rats.

The parametrial adipocytes of exercise-trained female rats were smaller and had greater rates of 2-deoxyglucose uptake and glucose oxidation over a wide range of insulin concentrations than the fat cells of sedentary animals of the same age. The fat cells of the sedentary animals had a 180% greater volume than those of the trained rats, despite only a 9% difference in body weight. Following cessation of training adipocyte size increased rapidly; approximately two-thirds of the initial difference in fat cell volume between the trained and sedentary rats had disappeared after 9 days without exercise. Concomitant with the increase in fat cell size, the response of 2-deoxyglucose uptake and glucose oxidation to insulin diminished. There was a close correlation between fat cell size and the magnitude of the response to insulin of both glucose oxidation and 2-deoxyglucose uptake. It appears from these results that the effect of exercise training on the response of adipocytes to insulin is rapidly lost when exercise is stopped.