Hunger
You must add a |reason= parameter to this Cleanup template – replace it with {{Cleanup|October 2006|reason=<Fill reason here>}}, or remove the Cleanup template.
Hunger is a feeling experienced by animals when the glycogen level of the liver falls below a certain point, usually followed by a desire to eat. The usually unpleasant feeling originates in the hypothalamus and is released through receptors in the liver and stomach. An average nourished human can survive about 50 days without food intake. Hunger can also be applied metaphorically to cravings of other sorts.
The term is commonly used more broadly to refer to cases of widespread malnutrition or deprivation among populations, usually due to poverty, political conflicts or instability, or adverse agricultural conditions (famine). (See malnutrition for statistics and other information on hunger as a political and economic problem.)
Hunger as a condition
The term hungry is commonly used to mean having an appetite for food or to be ready for a meal. After a long period without food, the mild sensation of hunger associated with being ready for a meal becomes progressively more severe, until it is acutely painful. As hunger grows, most living things will experience some internal effects. In humans and other animals, hunger can cause a gurgling sound with a bubbling feeling in the small intestine (many mistakenly think the stomach does this), and can shrink the stomach. Prolonged hunger will drive people to eat substances with no nutritional value (such as grass and soil) simply to fill their stomachs, but doing so actually has an adverse effect on energy balance as energy is still required to digest these substances.
Sometimes hunger is defined as the condition in which an organism can only use its protein tissue (e.g. muscles) as the source of energy, a state which sets in after all sugars and fats etc. are used up. [citation needed]
Extreme hunger is a symptom of diabetes [1].
In contrast to hunger, which is involuntary, fasting is the practice of voluntarily not eating for a period of time. A hunger strike is fasting for the purpose of nonviolent resistance.
Number of People Living in Hunger
According to The Borgen Project over 800 million people across the globe live in hunger. The condition is preventable and in September of 2000, the largest gathering of world leaders ever assembled met at a summit in New York City and agreed to a plan to end it by 2015. Known as the U.N. Millennium Goals, the plan to end world hunger has been agreed to by every nation on earth, but has received limited attention from the White House.
Physiology
Hunger is mediated by several molecular signalling pathways in mammals. Hormones known to affect hunger include ghrelin, leptin, and Peptide YY3-36 [2].
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.