Hunger

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This article is about the physical sensation of hunger. For a discussion of hunger as a political and economic problem, see Malnutrition. For other uses, see Hunger (disambiguation).

Hunger is a feeling experienced when the glycogen level of the liver falls below a threshold, usually followed by a desire to eat. The usually unpleasant feeling originates in the hypothalamus and is released through receptors in the liver. Although an average nourished human can survive about 50 days without food intake [1], the sensation of hunger typically begins after several hours without eating.

Hunger can also be applied metaphorically to cravings of other sorts, e.g. "hungry for victory."

[edit] Satiety

Satiety, or the feeling of fullness and disappearance of appetite after a meal, is a process mediated by the ventromedial nucleus in the hypothalamus. It is therefore the "satiety centre".

Various Hormones, first of all cholecystokinin, have been implicated in conveying the feeling of satiety to the brain. Leptin increases on satiety, while ghrelin increases when the stomach is empty.

Therefore, satiety refers to the psychological feeling of "fullness" or satisfaction rather than to the physical feeling of being engorged, i.e. the feeling of physical fullness after eating a very large meal.

Satiety directly influences feelings of appetite that are generated in the limbic system, and hunger that is controlled by neurohormones, especially serotonin in the lateral hypothalamus.