Hunger
The opposite of hunger is called 'satiety' or 'fullness'. The feeling is started in the hypothalamus, and hormones are released from the liver. People who have eaten can survive weeks without eating, but they will start to feel hungry after they have not eaten for a few hours. Hunger is generally considered quite uncomfortable. People who have eaten food usually will feel less hungry, or not hungry at all. People can live longer without food than without water.