From Citizendium, the Citizens' Compendium
Eat : The act of chewing food which involves ingestion and digestion, which brings nourishment to the human body giving it sustenance and enabling it to stay alive. It is a vital biological need; a person who doesn't or can't eat will lack sufficient energy to enable metabolism at the cellular level. Eating is done every day unless a person is fasting. Before eating, a person usually feels hungry.