Calorically restricted diets have been researched with rats and primates. They are finding that these animals live about 20% longer when they consume 30% of the normal diet eaten by the species researched. Many figure this will apply to humans. There are now groups that eat these calorically restricted diets. Obviously they look very thin. Doing it an a group with a common mission is the best way to do this. Eat less, live longer!