From Wikipedia, the free encyclopedia - View original article
Hunger is a sensation experienced when one feels 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, however, it differs from hunger; it is the desire to eat food without a physiological need. The often unpleasant feeling of hunger originates from the hypothalamus releasing hormones that target receptors in the liver.[dubious ] 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.
Hunger is also the most commonly used term to describe the condition of people who suffer from a chronic lack of sufficient food and constantly or frequently experience the physical sensation of hunger.
When hunger contractions start to occur in the stomach, they are informally referred to as hunger pangs. Hunger pangs usually do not begin until 12 to 24 hours after the last ingestion of food. A single hunger contraction lasts about 30 seconds, and pangs continue for around 30–45 minutes, then hunger subsides for around 30–150 minutes. Individual contractions are separated at first, but are almost continuous after a certain amount of time. Emotional states (anger, joy etc.) may inhibit hunger contractions. Levels of hunger are increased by lower blood sugar levels, and are higher in diabetics. They reach their greatest intensity in 3 to 4 days and may weaken in the succeeding days, although research suggests that hunger never disappears. Hunger contractions are most intense in young, healthy people who have high degrees of gastrointestinal tonus. Periods between contractions increase with old age.
The fluctuation of leptin and ghrelin hormone levels results in the motivation of an organism to consume food. When an organism eats, adipocytes trigger the release of leptin into the body. Increasing levels of leptin result in a reduction of one's motivation to eat. After hours of non-consumption, leptin levels drop significantly. These low levels of leptin cause the release of a secondary hormone, ghrelin, which in turn reinitiates the feeling of hunger.
Some studies have suggested that an increased production of ghrelin may enhance appetite evoked by the sight of food, while an increase in stress may also influence the hormone's production. These findings may help to explain why hunger can prevail even in stressful situations.
Hunger appears to increase activity and movement in many animals - for example, an experiment on spiders showed increased activity and predation in starved spiders, resulting in larger weight gain. This pattern is seen in many animals, including humans while sleeping. It even occurs in rats with their cerebral cortex or stomachs completely removed. Increased activity on hamster wheels occurred when rats were deprived not only of food, but also water or B vitamins such as thiamine. This response may increase the animal's chance of finding food, though it has also been speculated the reaction relieves pressure on the home population.
A food craving is an intense desire to consume a specific food, as opposed to general hunger. Similarly, thirst is the craving for fluids. Withdrawal craving is a "hunger" for administering addictive drugs.
|Wikiversity has learning materials about Hunger (motivational state)|
|Wikimedia Commons has media related to: Hunger (motivational state)|