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3.2: Hunger vs. Appetite

  • Page ID
    20949
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    Learning Objective
    • Describe what drives us to eat by using the concepts of appetite, hunger, and satiety, including the organs that are involved, as well as internal and external cues.

    Why Do We Feel the Urge to Eat?

    Two mechanisms prompt us to seek food, hunger and appetite. Hunger is a physiological drive for nonspecific foods. Appetite is a psychological desire to eat specific foods. Anorexia is a lack of appetite even when the physiologic need for food exists.

    The hypothalamus prompts hunger in response to various signals. The hypothalamus triggers feelings of either hunger or satiety (fullness) by integrating signals from nerve cells, hormones, and the amount and type of food we eat. 

    Nerve cells in the stomach and small intestine lining (that sense changes in pressure/fullness) send signals to the hypothalamus.

    Hormones are chemical messengers produced in specialized glands, secreted into the bloodstream, and target organs in other parts of the body. The following hormones are involved in hunger and satiety:

    • Insulin and glucagon are two hormones responsible for maintaining blood glucose levels.
      • When we have not eaten for a while, blood glucose levels fall, prompting a decrease in insulin levels and an increase in glucagon levels. This chemical message is relayed to the hypothalamus and triggers a feeling of hunger.
      • After we eat, the hypothalamus receives signals related to satiety including distention of the stomach and intestine, increased insulin levels, and decreased glucagon levels.
    • Ghrelin, CCK, and Leptin
      • Ghrelin is a hormone produced by the stomach. Levels are low immediately after a meal. As time continues without food, ghrelin levels rise and trigger a feeling of hunger.
      • CCK (cholecystokinin) is a hormone produced by the small intestine. As food enters the small intestine, CCK levels increase and trigger a feeling of satiety.
      • Leptin is a protein hormone that acts more long-term. Adipose (fat) cells produce leptin which triggers satiety. However, research currently suggests that obese people may be resistant to leptin's effects on satiety.

    The amount and type of food we eat can affect satiety. Foods containing protein have the highest satiety value. Bulky meals high in fiber and water provide satiety by stretching the stomach and small intestine. Beverages tend to be less satisfying than foods.

    Watch the following video for a review of the hormone control of hunger.

    "Hormone Control of Hunger" by khanacademymedicine


    3.2: Hunger vs. Appetite is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.