It's Never too Late

Experiments in species as diverse as yeast, worms, flies, and rodents emonstrate that dietary restriction prolongs survival. The encouraging findings of Mair et al. (1) on page 1731 of this issue now reveal that a lifetime of abstemiousness is not required to reduce one’s risk of death—at least in fruit flies. These investigators show that when flies fed a restricted diet are switched to a full diet, mortality soars to the level suffered by fully fed flies. Conversely, when the diet of fully fed Drosophila is restricted, mortality plunges within 2 days to the level enjoyed by flies that have xperienced a lifelong restricted diet.
The alliterative title of the Mair et al. paper—“Demography of Dietary Restriction and Death in Drosophila”—gives due credit to demography as the source of their new discovery.
Demographers have long realized that death rates provide age-specific information that cumulative survival curves cannot (2). Heeding this insight, Mair et al. analyzed the daily mortality of their fed and hungry flies. Demography offers a further lesson: Death of the frail alters the composition of a cohort, lowering subsequent mortality and possibly offsetting increases in mortality resulting from cumulative damage (3).......