Box 10 Anorexia nervosa (without low weight)

Anorexia nervosa (without low weight; also referred to as ‘atypical anorexia nervosa’; see “Background to eating disorders and how they occur” section for definition) is a diagnosis under the OSFED category in DSM-5. This requires all criteria for anorexia nervosa are met ‘except that despite significant weight loss, the individual’s weight is within or above the normal range.’ ‘Significant weight loss’ in this context has been defined in adult men and women as 5% or more of body weight accompanied by cognitive concerns about eating and weight [175]. Significant weight loss for adolescents, however, may be less according to developmental stage [19].

Anorexia nervosa (without low weight) is commonly, but falsely, perceived as being less severe than low weight anorexia nervosa. People with anorexia nervosa (without low weight) may be just as physically compromised and experience similar or higher levels of psychopathology compared with their peers with low weight anorexia nervosa [19, 20, 176]. For people with anorexia nervosa (high or low weight) requiring hospital admission, recent and total weight loss have been shown to be stronger predictors of many physical complications, such as bradycardia, than admission weight [19].

Behaviours and outcomes that are viewed as concerning in people of low weight, such as severe restriction and weight loss, are often praised and encouraged for people with higher weight and viewed as ‘helpful’ to the achievement of a weight loss goal. All people who have lost a significant amount of weight, either recently or in total, should be assessed for an eating disorder regardless of their weight. Clinicians should be cognisant that weight gain, regardless of BMI range, may be necessary as a part of recovery (see “Nutritional and medical management” section Malnutrition). Furthermore, the use of the broader ICD-11 diagnosis of anorexia nervosa without weight criterion (as is used in this guideline) is encouraged.