An eating disorder is a complex compulsion to eat in a way which disturbs physical and psychological health. The eating may be excessive (compulsive over-eating); too limited (restricting); may include normal eating punctuated with episodes of purging; may include cycles of binging and purging; or may encompass the ingesting of non-foods.

The best-known eating disorders are Anorexia nervosa and Bulimia nervosa. The most widely and rapidly spreading eating disorder is compulsive overeating or Binge eating disorder. The three most common eating disorders are anorexia, bulimia and binge eating disorder. All three have severe consequences to a person's health and can even cause death. There are numerous theories as to the causes and mechanisms leading to eating disorders.