the criteria have been met for a sustained period of time.
Specify current severity:
The minimum level of severity is based, for adults, on current body mass index (BMI) (see
below) or, for children and adolescents, on BMI percentile. The ranges below are derived
from World Health Organization categories for thinness in adults; for children and adoles-
cents, corresponding BMI percentiles should be used. The level of severity may be in-
creased to reflect clinical symptoms, the degree of functional disability, and the need for
supervision.
Mild:  BMI ≥ 17 kg/m2 
Moderate: BMI 16–16.99 kg/m2 
Severe:  BMI 15–15.99 kg/m2 
Extreme:  BMI < 15 kg/m2
Subtypes
Most individuals with the binge-eating/purging type of anorexia nervosa who binge eat
also purge through self-induced vomiting or th e misuse of laxatives, diuretics, or enemas.
Some individuals with this subtype of anorexia nervosa do not binge eat but do regularly
purge after the consumption of small amounts of food. 
Crossover between the subtypes over the c ourse of the disorder is not uncommon;
therefore, subtype description should be used to describe current symptoms rather than
longitudinal course.
Diagnostic Features
There are three essential features of anorexia  nervosa: persistent en ergy intake restriction;
intense fear of gaining weight or of becoming  fat, or persistent behavior that interferes
with weight gain; and a disturbance in self-perceived weight or shape. The individual main-
tains a body weight that is below a minimally normal level for age, sex, developmental tra-
jectory, and physical health (Criterion A). In dividuals’ body weights frequently meet this