Nutrition and Longevity in the Rat

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Abstract
On ad libitum feeding, rats attained large skeletal size and developed obesity. When food intake was restricted by 33 or 46%, levels which prevented fat accumulation and had little retarding effect on skeletal growth, longevity was extended and onset of disease was delayed. At 800 days of age only 48% of unrestricted male rats were alive as compared with 81 to 87% survival for restricted animals. Because most of the females remained alive at this age, a comparison between unrestricted and restricted animals could not be made. Comparative incidence of tumors and of cardiac, renal and vascular lesions at 800 days of age showed significant differences between unrestricted and restricted animals. In males frequency of lesions in unrestricted rats was 100% as compared with 64% incidence for the 33%-restricted rats and 24% for the 46%-restricted rats. Though more of the females, unrestricted and restricted, survived this experimental period, the difference in percentage of lesions in the two groups of females was striking. All of the females surviving to 800 days on restricted food intake were free from disease, while 57% of the unrestricted ones had lesions. The lower incidence and lesser severity of lesions in restricted females at 800 days indicated that life expectancy would be greater in restricted than in unrestricted females observed for longer periods. Optimum weight and skeletal size in relation to disease and life expectancy were below maximum measurements. Also, hormonal as well as dietary factors seem to play a role in the greater longevity of the female as compared with the male. The extended longevity of the restricted rats was not associated with immaturity.

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