Healthy people eat when they are hungry and stop when they are satisfied. Those with eating disorders do not have the same contact with their real hunger and satisfaction feelings. They eat or starve when their feelings are unbalanced. It is difficult for them to separate hunger from other unpleasant sensations. A bulimic might also eat compulsively when starved, because of previous starvation or vomiting. More.
When different feelings cannot be separated, the necessary information for managing the underlying problems properly is unobtainable. In normal people, thoughts, feelings and physical signals tell us what must be done in order to function as well as possible. Those who get the wrong information become confused and can't use their knowledge and feelings in order to manage their problems correctly.