Eating Disorders

Eating disorders are a group of psychiatric conditions characterised by persistent disturbance of eating behaviour and associated distressing thoughts and emotions about food, weight and body shape.

They include anorexia nervosa, bulimia nervosa, binge eating disorder, avoidant restrictive food intake disorder, pica and rumination disorder.

The physical and psychological consequences frequently overlap substantially regardless of subtype, so recognition, initial assessment and medical risk principles are shared across the group.

Accurate diagnosis and specialist informed early intervention are directly relevant to long term outcome.

Classification and shared principles

• Restrictive eating disorders (anorexia nervosa and avoidant restrictive food intake disorder) share the core feature of inadequate energy intake relative to requirement. The risk is malnutrition and its medical complications.
• Avoidant restrictive food intake disorder is characterised by food avoidance or restriction not driven primarily by weight or shape concerns, which distinguishes it from anorexia nervosa.
• Binge purge pattern disorders (bulimia nervosa, and the binge purge subtype of anorexia nervosa) are characterised by recurrent binge eating followed by compensatory behaviours. These are self induced vomiting, laxative misuse, excessive exercise, or misuse of other medications including diuretics or, in individuals with diabetes, deliberate insulin omission.
• The medical risk in binge purge disorders relates predominantly to the specific compensatory behaviours employed.
• Binge eating disorder is characterised by recurrent binge eating episodes without the regular compensatory behaviours of bulimia nervosa. Its medical risk profile relates more closely to the metabolic consequences of the binge eating pattern itself.

• Behavioural and psychological features vary by subtype (see the individual conditions). Shared features frequently include preoccupation with food, weight and body shape, disturbed body image, and significant distress or functional impairment.
• Medical complications depend on the pattern of disordered eating behaviour.
• Severe caloric restriction produces bradycardia, hypotension and amenorrhoea (see anorexia nervosa). With sufficiently severe or prolonged restriction there is a significant risk of refeeding syndrome on nutritional rehabilitation.
• Purging behaviours produce electrolyte disturbance, dental erosion and oesophageal injury (see bulimia nervosa).
• Eating disorders frequently coexist with other psychiatric conditions, particularly depression, anxiety disorders and obsessive compulsive disorder. Assess carefully and sensitively for these.
• The suicide risk associated with this group is significant and well recognised. Enquire explicitly and directly.
• Presentation may occur across a wide age range and in any gender. Onset most classically occurs in adolescence and young adulthood. Presentation is increasingly recognised in older adults, in men, and across the full spectrum of body weight.
• This includes normal weight and higher weight individuals with significant restrictive or purging behaviour. The historical assumption that eating disorders are confined to visibly underweight individuals is now recognised as inaccurate. It has contributed to diagnostic delay and undertreatment in patients without this stereotyped appearance.

• Diagnosis rests on a detailed, sensitively conducted clinical history. Explore eating patterns, compensatory behaviours, body image concerns, and their impact on daily functioning. Use validated screening tools where indicated to support structured assessment.
• Every assessment includes physical assessment: weight and height with body mass index, vital signs (specifically bradycardia and postural hypotension), and a general physical examination.
• Interpret body mass index with caution, in the context of the individual's own weight history and trajectory, not as an isolated diagnostic threshold. Clinically significant, high risk eating disorders occur across the full weight spectrum.
• Baseline laboratory investigation supports medical risk assessment: full blood count, a full electrolyte panel, and renal and liver function. Pay specific attention to potassium, magnesium and phosphate, which are particularly relevant to purging related and refeeding related risk.
• In individuals with amenorrhoea, assess bone density where restriction has been prolonged.
• Electrocardiography is essential in any patient with significant weight loss, bradycardia, or electrolyte disturbance, because of the risk of cardiac arrhythmia in this population.
• Use an appropriate, validated risk stratification framework, incorporating physical and biochemical findings and the behavioural pattern, to structure medical risk assessment.
• The result guides the urgency of intervention and the setting of care (outpatient, day patient, or inpatient medical or specialist eating disorder unit admission).

• Management requires a coordinated, multidisciplinary approach integrating medical, nutritional and psychological or psychiatric treatment. Individualise the balance and intensity of each component to the diagnosis, severity and medical risk level.
• Medical stabilisation takes priority where significant medical risk is identified. Hospital admission is indicated for severe bradycardia, significant postural hypotension, significant electrolyte disturbance, or other markers of high medical risk (see anorexia nervosa and refeeding syndrome for the critical considerations in nutritional rehabilitation).
• Psychological therapy is the core, definitive treatment across the eating disorder spectrum. Evidence based approaches include family based treatment, particularly effective in adolescent anorexia nervosa, and cognitive behavioural therapy adapted for eating disorders, effective across several subtypes including bulimia nervosa and binge eating disorder.
• Nutritional rehabilitation, guided by specialist dietetic input, is essential for restrictive eating disorders. Individualise its pace and approach, because avoiding refeeding syndrome in significantly malnourished individuals is critical (see refeeding syndrome).
• Referral to a specialist eating disorder service, where available, is generally appropriate for confirmed or strongly suspected cases, given the complexity of these conditions and their medical and psychiatric risk.
• Primary care or general medical teams provide initial medical risk assessment and ongoing physical health monitoring. They also provide interim supportive care while awaiting specialist input, which is particularly relevant given typical waiting times for specialist psychological treatment.
• Involve and support family and carers where appropriate and with the patient's consent.
• Engage the patient collaboratively and without judgement, because ambivalence toward treatment is frequently significant, particularly in anorexia nervosa.
• Provide ongoing, longitudinal follow up, because the course is frequently prolonged and sometimes relapsing and remitting.