The concept of caloric restriction is as old as humanity itself. In Japan where you eat until you are only 80% full this is called hara hachi bunme, the islamic concept were you reserve 1/3 for your food, 1/3 for your liquids, and 1/3 for your breath in your stomach, soundly represents the yogic mitahara, with half the space for food 1/4 for liquids and 1/4 for air. Pythagoras, Jesus, Buddha, Muhammad, they all fasted for 40 days, ramadan still commemorating this idea.