Anorexia nervosa is a complex eating disorder with three key features. It's only human to wish you looked different or could fix something about yourself. But when a preoccupation with being thin takes over your eating habits, thoughts, and life, it's a sign of an eating disorder.Refer this link to know more on this:
http://www.helpguide.org/mental/anorexia_signs_symptoms_causes_treatment.htm