ADIPOSE-TISSUE CELL-SIZE AND LIPOLYSIS IN RAT - RESPONSE TO EXERCISE INTENSITY AND FOOD RESTRICTION

Two levels of treadmill exercise and 3 levels of food restriction were imposed on male rats over a 12-wk experimental period to create a distribution of adipose tissue cell sizes. Epinephrine-stimulated lipolysis [ESL] was subsequently measured in the isolated adipocytes from rats trained at 2 different exercise levels and in untrained rats fed either ad libitum or 16%, 27% or 35% dietary restriction. Energy restriction was effective in reducing body weight and to some extent epididymal fat pad weight; adipocyte size and number were not significantly affected. Exercise in both groups of trained rats was effective in reducing adipocyte size, but, cell size did not differ between training groups. The group receiving the greatest amount of daily exercise had significantly greater ESL indicating that the adaptive increase in lipolytic potential seen in adipose tissue of exercise trained rats is a true metabolic adaptation not secondary to reduced cell size.