Hunger is a sensation that represents the physiological need to eat food. In contrast, satiety is the absence of hunger; it is the sensation of feeling full. Appetite is another sensation experienced with eating; it is the desire to eat food. There are several theories about how the feeling of hunger arises. A healthy, well-nourished individual can survive for weeks without food intake, with claims ranging from three to ten weeks. The sensation of hunger typically manifests after only a few hours without eating and is generally considered to be unpleasant.