THE EFFECTS OF DIETARY CALORIC RESTRICTION ON MATURITY AND SENESCENCE, WITH PARTICULAR REFERENCE TO FERTILITY AND LONGEVITY

Abstract

Calorie underfed [female] mice of the A strain show a fertility index of 0.08 litter/ mouse/month during the period to 8 mos. of age, and 0.04 thereafter. When previously underfed [female] [female] are allowed food ad libitum at 8 mos. of age, their fertility index rises to 0.65 litter /mouse/month, which approximates the normal for young full-fed [female] [female]. It is concluded that maturation with respect to reproductive capacity is retarded or postponed when low calorie feeding is imposed through a large fraction of the avg. normal life-span. The calorie underfeeding did not prevent subsequent maturation and normal gestation at an age when full-fed littermate sisters had become nearly sterile from senility, showing a fertility index of only 0,05 litter/mouse/mo. In the expts. reported, 25% of A strain 9 mice subjected to life-time caloric restriction were alive at an age when all of their full-fed littermate sisters had died. Considering the survival beyond 240 days in these expts., the 50% mortality times for the life-time calorie-restricted group, the 8 mo. restricted, subsequently full-fed group, and the full-fed controls were 200, 140 and 125 days, respectively. Some factors influencing the significance of these observations were discussed. The caloric restriction employed in these studies retarded sexual maturation but did not prevent its occurrence upon subsequent full-feeding, and was associated with a tendency toward a longer life-span. Caloric restriction for 240 days, with subsequent full-feeding, did not prevent a significant incidence of mammary carcinoma although it increased the avg. cancer age above that in comparable non-virgin, fully fed controls.