Energy restriction, also known as caloric restriction (CR), is the most robust and reproducible means of reducing age-related diseases and extending life span in short-lived animals, but the effects in humans are unknown. Preliminary data from ongoing research with CR on long-lived nonhuman primates (rhesusandquirrel monkeys)also suggest potential health benefits—although it will take some years before final results become available and firmer conclusions can be reached regarding aging and life span.
Some epidemiologic and short-term human studies support CR-related health benefits. However, a role for CR in human aging is difficult to ascertain since human life span makes long-term investigations impractical and there are no universally accepted biomarkers to measure the rate of human aging. Whether CR (without malnutrition) affects human aging may be among the most significant unanswered questions in modern biogerontology. Yet we have few available human populations or studies that can address this question. Most human populations who have experienced low calorie intake have suffered from high mortality due to infectious diseases and malnutrition.