Aging. It's never too late.
When organisms as diverse as yeast and rodents are subjected to a restricted diet, they live longer. The good news is, according to Vaupel, Carey, and Christensen in their Perspective, that switching to a restricted diet at any age can yield the benefit of increased longevity--at least in flies (Mair et al.).
D000368:Aged; D000375:Aging; D000818:Animals; D031204:Caloric Restriction; D003710:Demography; D004032:Diet; D004330:Drosophila / Q000502:physiology*; D005260:Female; D006801:Humans; D008136:Longevity; D008297:Male; D009026:Mortality; D012098:Reproduction; D012306:Risk; D012377:Rodentia; D012726:Sexual Behavior, Animal; D013997:Time Factors