Hunger is an inborn feeling, but training is needed in order to be aware of it and use it in a suitable way.
To feel hunger and distinguish it from other feelings is not inborn, but is learned. The belief that the experience of hunger is exclusively inborn has made it difficult to understand how eating disorders function. The ability to feel real hunger and satisfaction can also be harmed by fast slimming or starvation.
See also "How should one bring up children so that they do not develop eating disorders" and "Genetic factors predisposing to eating disorders".
You need to be able to differentiate between the physical need for nutrition and the individual's ability to experience these needs to be able to understand how an eating disorder works. The ability to recognize true hunger can be disrupted by lack of food and undernourishment. Even rats need to learn about how to experience hunger and satiation to be able to eat in a proper way. In humans, whose brains are much more complex, the ways of learning are also more complicated. It's easy to forget the importance of learning for the ability to experience hunger if you only picture the function as an innate desire, a basic part of the organism's physiological inheritance, which only can be superficially modified by environment.
People who do not have eating disorders keep approximately the same weight year after year, and eat between 2000 and 3000 calories a day. Picture a person who eats around 2500 calories a day. If that person increased his eating by merely one percent, to 2525 calories a day, he would gain several pounds a year. Since their weight does not increase, the satisfaction and hunger must be so precise that it doesn't even err by a single percent. To be able to regulate this exactly, the brain combines signals from, for example, the stomach (how full it is), the intestines (enzymes as a result of the decomposition of fat), the blood (the level of blood sugar), taste and scents, and the knowledge of what you just have been eating. It is not strange at all that this complex process can easily be disturbed by faulty learning and emotional trauma. More.
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