From the University at Buffalo: "Severely restricting calories leads to a longer life, scientists have proved. ... such a diet also can maintain physical fitness into advanced age, slowing the seemingly inevitable progression to physical disability and loss of independence. The study, using a rat model of life-time caloric restriction, showed that the diet reduces the amount of visceral fat, which expresses inflammatory factors that in humans cause chronic disease and a decline in physical performance and vitality across the lifespan. ... This is the first study to report that caloric restriction reduced production in visceral fat of the inflammatory cytokine IL-6 and enhanced performance on overall physical function assessments ... In addition, rats that ate a normal diet lost a significant amount of lean muscle mass and acquired more fat, while calorie-restricted rats maintained lean muscle mass as they aged." You'll find more about fat, inflammation and the damage that causes aging in the Fight Aging! archives. Remember that the human practice of CR should properly be called "calorie restriction with optimal nutrition" - it's not just cutting calories, but rather eating optimally. You can find out all about the nuts and bolts of practicing CR at the Calorie Restriction Society.