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Eating disorders 

Eating disorders

Eating disorders

Christopher G. Fairburn


November 28, 2012: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

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date: 30 March 2017

Eating disorders affect about 5% of adolescent girls and young adult women. They are much less common among men. They typically begin in adolescence and may run a chronic course, interfering with psychological, physical, and social functioning.

Three eating disorders are distinguished: (1) anorexia nervosa; (2) bulimia nervosa; and (3) a residual diagnostic category—the most common seen in routine clinical practice— termed ‘eating disorder not otherwise specified’ (eating disorder NOS). They all share a distinctive ‘core psychopathology’, the overevaluation of shape and weight, and patients frequently move between the categories, hence a case may be made for adopting a ‘transdiagnostic’ perspective.

The aetiology of the eating disorders is complex and ill-understood: there is a genetic predisposition, and some specific environmental risk factors have been implicated.

Clinical features and diagnosis

In anorexia nervosa the pursuit of weight loss leads patients to engage in a severe and selective restriction of food intake, with foods viewed as fattening being avoided. The same eating habits are seen in patients with bulimia nervosa, the main distinguishing feature being that the attempts to restrict food intake are punctuated by repeated episodes of binge eating. Three subgroups within eating disorder NOS may be recognized: (1) those that just fail to meet diagnostic criteria for anorexia nervosa or bulimia nervosa; (2) those that are mixed in character between anorexia nervosa and bulimia nervosa; and (3) binge eating disorder.

Aside from low body weight (body mass index <17.5), a wide range of physical abnormalities is present in anorexia nervosa, some of which can be life-threatening, e.g. cardiac arrhythmia. These appear to be largely secondary to the disturbed eating habits and compromised nutritional state: most are reversed by restoration of healthy eating habits and sound nutrition. The weight of most patients with bulimia nervosa is in the healthy range (body mass index 20–25) due to the effects of the undereating and overeating cancelling each other out.

The diagnosis of an eating disorder is made on positive grounds by using the history and mental state examination to detect the characteristic behavioural and attitudinal features—not by simply ruling out possible physical causes.


Eating disorders are difficult to treat and impose a significant burden on health services.

Bulimia nervosa—in this condition: (1) the most effective treatment is a specific type of cognitive behaviour therapy (CBT) that focuses on modifying the specific behaviours and ways of thinking that maintain these conditions; (2) antidepressant drugs have an ‘antibulimic’ effect; and (3) no consistent predictors of outcome have been identified.

Anorexia nervosa—there is little evidence on which to base treatment, but it would generally be agreed that the following aspects are important: (1) patients need to be helped to see that they need change; (2) weight needs to be restored; (3) patients’ overevaluation of shape and weight, their eating habits, and their general psychosocial functioning all need to be addressed, perhaps in younger patients by family-based treatment.

Eating disorder NOS—there is very little information regarding treatment, but an adaptation of the CBT for bulimia nervosa appears to be useful.

Prevention—the idea of trying to stop schoolgirls from developing eating disorders is clearly attractive, but there is a danger of magnifying concerns about shape and weight rather than reducing them, and there is potential for conflict between emphasis on the risks of undue dieting and advice directed at the prevention of obesity.

Acknowledgement: Christopher G Fairburn is supported by a Principal Research Fellowship (046386) from the Wellcome Trust.

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