The vernacular has a "bear hunger" and the advertising speaks of the "small hunger in between". But what exactly is hunger? It arises when the body's energy stores are empty, that is, after we have not eaten or exercised for a long time. Hunger is the craving for food and energy. Most people feel it in the stomach, but also lack of concentration, headache or nausea can be signs.
Pure head thing: hunger arises in the brain
The central hub for hunger is the brain, more specifically the diencephalon (the hypothalamus). This is where all the messages concerning the energy state of the body come together. Thus, it measures the energy reserves and at the same time regulates hunger and satiety.
If the signals of the diencephalon are ignored for a long time, cravings arise. In a feeding attack indiscriminately food is "thrown".
Many people, however, feel hungry because of repeated diets and frequent snacking. The appetite on the other hand serves the pleasant side of the meal - the enjoyment. Appetite awakens the appetite for a certain dish, even if one is actually already full.
How the body regulates hunger and appetite during a meal is a complicated process. Before and at the beginning of the meal, the look, smell and taste of a meal determines what and how much we eat. Receptors of the stomach and intestinal wall send out information about their state of filling and the nutrients of the food. The brain then lowers the appetite, the size of the meal is regulated. After the nutrients from the intestine have entered the body and liver, their receptors react to the various degradation products and affect their saturation.
How long we are full of food depends on the composition of the food. Carbohydrates saturate quickly, while fats and proteins last long.