Hunger

This article is about the physical sensation. For "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,^{[citation needed]} usually followed by a desire to eat. The often unpleasant feeling originates in the hypothalamus and is released through receptors in the liver. Although an average nourished human can survive weeks without food intake,How long can someone survive without water?. Retrieved on 2007-05-14. the sensation of hunger typically begins after a couple of hours without eating and is generally considered quite uncomfortable. The sensation of hunger can often be alleviated and even mitigated entirely with the consumption of food.

Hunger pangs

When hunger contractions occur in the stomach, these are called hunger pangs. Hunger pangs usually do not begin until 12 to 24 hours after the last ingestion of food, in starvation. A single hunger contraction lasts about 30 seconds, and pangs continue for around 30-45 minutes, then hunger subsides for around 30-150 minutes.A. J. Carlson (1931) Hunger The Scientific Monthly 33: 77-79. 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, though hunger never disappears.A. J. Carlson; F. Hoelzel (1952) The Alleged Disappearance of Hunger during Starvation Science 115: 526-527. Hunger contractions are most intense in young, healthy people who have high degrees of gastrointestinal tonus. Periods between contractions increase with old age.

Biological mechanisms

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 results in a reduction of one\'s motivation to eat. OMIM - LEPTIN; LEP After hours of non-consumption, leptin levels drop significantly. These low levels of leptin cause the release of secondary hormone, ghrelin, which in turn reinitiates the feeling of hunger.

Behavioral response

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.Provencher, L.; Riechert, S.E. (1991) Short-Term Effects of Hunger Conditioning on Spider Behavior, Predation, and Gain of Weight Oikos 62:160-166 This pattern is seen in many animals, including humans while sleeping.Wald, G.; Jackson, B. (1944) Activity and Nutritional Deprivation Proceedings of the National Academy of Sciences of the United States of America 30:255-263 It even occurs in rats with their cerebral cortex or stomachs completely removed.George Wald: The Origin of Death. Retrieved on 2007-05-14. Increased activity on hamster wheels occurred when rats were deprived not only of food, but also water or B vitamins such as thiamineGuerrant, N.B., Dutcher, R.A. (1940) Journal of Nutrition 20:589. 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.

See also

• Starvation
• Fasting
• Thirst
• Appetite Suppressants
• Hypoglycemia
• Eating disorder

References

External links

• Intergovernmental Institution for the use of Micro-algae Spirulina Against Malnutrition (IIMSAM)
• Fighting Hunger and poverty in Ethiopia (Peter Middlebrook)
• Satiety enhancers in food Scientist Live
• e-learning about Food Security and Hunger from FAO

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