Many studies have shown that animals on calorie restricted diets live longer, have less diabetes, heart attacks and cancers and appear younger. In the latest work at the Wisconsin National Primate Research Center, monkeys eating only 30 percent of their normal caloric intake live much longer and appear much younger than those eating their full diets (American Journal of Physiology-Endocrinology and Metabolism, August 2006).
Nobody really knows how calorie restriction with adequate nutrients prolongs life and prevents disease, or whether the animal studies can be applied to humans. The leading theory for calorie restriction with adequate nutrition is that it teaches your mitochondria to burn food to produce much lower amounts of oxidants. Mitochondria are the furnaces in cells that turn food into energy. Converting food to energy produces free electrons that form reactive chemicals called oxidants that can bind to and damage DNA and shorten life. Exercise also reduces the amount of oxidants and so should prolong life. Another theory is that excess calories cause fat cells to fill up with fat. Full fat cells produce cytokines that turn on your immunity to cause inflammation that damages all the cells in your body, which would shorten life and cause disease. Anything that prevents excess fat storage should reduce inflammation and thus prolong life. Exercise burns calories, and food restriction lowers calorie intake in humans as well as animals.
I read info about this years ago, in one of Helen Gurley Brown's diet tips. Scientists have been noticing this for a long time. It's funny -- I would have thought that evolutionary wise, the people who ate more would survive longer... I mean, those are the people who were better hunters, leaders, plotters. I love food, though. I wonder if they will invent something during my lifetime that lowers the cellular inflammation.