Why do many people desire ice cream and pie or some other rich dessert after eating a huge Thanksgiving dinner? This desire is referred to as appetite, which is not the same as hunger. Appetite is a complicated phenomenon, linking biology with environment. It is a biopsychological system, meaning it is the result of both our biology (hunger) and psychology (desires and feelings).
Hunger, on the other hand, is purely biological. It is that nagging, irritating feeling that makes one think about food and the need to eat. It gets stronger the longer one goes without food, and it weakens after eating. Although the physiological reasons people feel hunger have not been clearly identified, the feeling of hunger rises and falls based on the activation of neural circuitry related to eating. There are many chemical agents in the human body that affect the sensation of hunger. Unfortunately for some people, eating behavior is not governed by hunger and satiety (feeling of fullness), but by a variety of other factors. For example, some people eat in response to their feelings of anxiety, depression, or stress. Eating temporarily helps lessen these feelings, and thus tends to become a coping response whenever they have these bad feelings.
Weight gain may occur if people eat for reasons other than hunger. One strategy to help people manage their weight is for them to learn to differentiate between appetite and hunger, to learn to “listen to their bodies,” and to eat only when they are hungry—and to stop when they are full. Hunger-control medications can help reduce the biological need to eat, but people still need to manage their psychological feelings about eating.