Scientists have known about the longevity benefits of caloric restriction since experiments in the 1930s showed that rats lived much longer if their food intake was severely restricted. Broadly speaking, the reason is stress. Although usually viewed as the enemy of good health, stress can actually boost longevity, driving an organism to slow down metabolism and conserve scarce resources. Caloric restriction is one form of stress that does this very effectively. But to see the longevity benefits, animals must eat only about half the calories in a normal diet, resulting in constant hunger. Now, Harvard Medical School researchers have discovered a way to genetically mimic the life-extending effects of calorie restriction — without the severe food deprivation that method entails. The findings might someday lead to drugs that give people longer, healthier lives. Previous studies have shown that a key component in the longevity pathway is the Sir2 protein, “one of the most exciting molecules in aging research,” says David Sinclair, Harvard Medical School assistant professor of pathology, and senior author of the new research. The research appeared in the May 24, 2002, Journal of Biological Chemistry.