The number of adolescent patients with anorexia nervosa is increasing. In addition, an increase in pre-adolescent patients with premenarchal onset has also been recognized. Detection of the disease in childhood and adolescence, however, is not always easy because the symptoms are not characteristic during this period. This study was performed to investigate detection of anorexia nervosa in children/adolescents by comparing energy and nutrient intake between patients with anorexia nervosa and healthy thin persons.