Changes in adipose mass and cellularity through the adult life of rats fed ad libitum or a life-prolonging restricted diet.

Male Fischer 344 rats were either fed ad libitum (Group A) or 60% of the ad libitum intake (Group R) starting at 6 weeks of age; the latter is a life prolonging food restriction. Total adipose mass increased with increasing age in both Group A and Group R rats until about 70% of the life span after which it declined. The results indicate that the lower adipose mass of the Group R rats is probably not related to life prolongation. Adipocyte hypertrophy is involved in growth of the epididymal and perirenal depots in adult Group R rats and is the sole basis of epididymal depot growth in adult Group A rats. Increasing adipocyte number is the sole basis of perirenal depot growth in adult Group A rats and is involved in the growth of both depots in adult Group R rats. Decreasing adipose mass during senescence involves decreasing mean adipocyte volume but not a decrease in the adipocyte number.