"Eating disorder" is when a person eats, or refuses to eat, in
order to satisfy a psychic need and not a physical need. The person
doesn't listen to bodily signals or perhaps is not even aware of them. A normal person eats when hungry and stops eating when the body doesn't need more, when he feels the signal of satisfaction.
Eating disorders are usually classified as
anorexia nervosa
,
bulimia nervosa
or
binge eating disorder
in accordance with the symptoms. However, a person may have an
eating disorder without belonging exactly to any of these
categories.
Those who lose weight because of illness, e.g., cancer, are not considered to have an eating disorder.