Survival, body weight, and spontaneous neoplasms in ad Libitum-fed and food-restricted Fischer-344 rats.

Ad libitum-fed (AL) and food-restricted (FR) Fischer-344 male and female rats were monitored for survival, body weight, and spontaneous neoplasms. Mean and maximal lifespans for each group were inversely related to mean body weights. AL males were the shortest lived (mean lifespan 101 wk) followed by AL females (118 wk), FR males (125 wk), and FR females (132 wk). Gross and microscopic examinations were performed on 851 rats from cross-sectional and longevity components of the study. In FR groups, the incidence of mammary gland fibroadenomas, testicular interstitial cell tumors, and pituitary neoplasms was decreased while the latency of these neoplasms was increased. In longevity components, most FR groups had a higher incidence of leukemia than AL cohorts, but all FR groups had a higher mean age at death for the rats with leukemia. Higher leukemia rate in the FR groups was thought to be a result of their extended mean lifespan.