Key Facts

Eating disorders are characterised by disturbed eating behaviours, body image distortion, and associated physical and psychological consequences. They are among the most lethal psychiatric conditions.

Epidemiology

Eating disorders affect approximately 1.25 million people in the UK. Anorexia nervosa prevalence ~0.3-0.5%; bulimia nervosa ~1-2%; binge eating disorder ~2-3%. Peak onset in adolescence and young adulthood. F:M ratio approximately 10:1 for anorexia, 3:1 for binge eating disorder. Increasing recognition in males and older adults.

Aetiology

• Biological: Genetic heritability ~50-80% for anorexia; serotonergic and dopaminergic dysfunction; reward pathway alterations
• Psychological: Perfectionism, low self-esteem, body dissatisfaction, need for control, trauma
• Sociocultural: Thin-ideal internalisation, diet culture, social media, occupational pressure (dance, athletics, modelling)
• Family factors: Enmeshment, overprotection, family conflict (though causal role debated)

Pathophysiology

Starvation effects (anorexia nervosa):

• Hypothalamic-pituitary-gonadal axis suppression → amenorrhoea
• Reduced metabolic rate, hypothermia, bradycardia
• Bone loss (osteoporosis) — oestrogen deficiency + cortisol excess + nutritional deficiency
• Cardiac muscle wasting → arrhythmias, QTc prolongation
• Refeeding syndrome risk — phosphate, potassium, magnesium depletion

Purging effects (bulimia):

• Hypokalaemic metabolic alkalosis (vomiting) or metabolic acidosis (laxative abuse)
• Dental erosion (perimolysis), parotid gland enlargement
• Mallory-Weiss tears, oesophageal rupture (rare)

Anorexia Nervosa

• Significantly low body weight (BMI <17.5) through restriction ± purging
• Intense fear of gaining weight despite being underweight
• Body image distortion — overestimation of body size
• Amenorrhoea (no longer required for diagnosis but often present)
• Subtypes: Restricting type vs binge-purge type

Bulimia Nervosa

• Recurrent binge eating (≥1/week for ≥3 months) with compensatory behaviours
• Compensatory: Self-induced vomiting, laxative abuse, excessive exercise, fasting
• Normal or slightly above-normal weight
• Self-evaluation unduly influenced by body shape/weight

Binge Eating Disorder

• Recurrent binge eating without regular compensatory behaviours
• Eating rapidly, until uncomfortable, when not hungry, alone, feeling disgusted/guilty
• Marked distress about binge eating
• Often overweight or obese

Red Flags — Medical Emergency

• BMI <13 or rapid weight loss >1kg/week
• Heart rate <40 bpm, QTc prolongation
• Potassium <2.5 mmol/L or other severe electrolyte disturbance
• Syncope, chest pain, muscle weakness
• Hypothermia (<35°C), dehydration
• Suicide risk (elevated in all eating disorders)

Bedside

• BMI: Weight and height — BMI <17.5 (AN), <15 (severe), <13 (critical)
• Vital signs: HR, BP (lying and standing — postural drop), temperature
• ECG: QTc prolongation, bradycardia, U waves (hypokalaemia)
• SIT-UP-SQUAT-STAND (SUSS) test: Proximal muscle strength

Bloods

• U&Es: Hypokalaemia (vomiting/laxatives), hyponatraemia, raised urea
• FBC: Pancytopenia (bone marrow suppression in severe AN)
• LFTs: Raised in starvation or refeeding
• Phosphate, magnesium, calcium: Refeeding risk assessment
• Glucose: Hypoglycaemia in severe AN
• TFTs: Low T3 (sick euthyroid), exclude hyperthyroidism
• Bone profile + vitamin D: Osteoporosis risk
• Amylase: Elevated in vomiting (salivary amylase)
• LH, FSH, oestradiol: Hypothalamic-pituitary-gonadal suppression

Imaging

• DEXA scan: Osteoporosis assessment if amenorrhoea >12 months or BMI <15
• Echocardiogram: If cardiac symptoms or very low BMI

Special Tests

• EDE-Q: Eating Disorder Examination Questionnaire — measures severity
• SCOFF questionnaire: Screening (5 questions: Sick, Control, One stone, Fat, Food)

Non-pharmacological (NICE NG69)

Anorexia nervosa:

• Children/adolescents: Family-based treatment (FBT/Maudsley model) — first-line; parents take control of feeding
• Adults: Individual eating-disorder-focused CBT (CBT-ED), MANTRA (Maudsley Anorexia Nervosa Treatment for Adults), or SSCM (Specialist Supportive Clinical Management)
• Nutritional rehabilitation: Dietitian-led, gradual increase (avoid refeeding syndrome)
• MARSIPAN guidelines: Medical management of severely ill patients

Bulimia nervosa:

• CBT-BN (CBT for bulimia nervosa): 16-20 sessions — first-line
• Guided self-help: Based on CBT principles — step 1

Binge eating disorder:

• Guided self-help based on CBT — first-line
• Group CBT if guided self-help ineffective

Pharmacological

• Fluoxetine 60mg OD: Evidence for bulimia nervosa (reduces binge-purge frequency) — NOT first-line for anorexia nervosa
• Olanzapine: Small evidence base for weight gain in severe AN (off-label)
• SSRIs: For comorbid depression/anxiety (after weight restoration in AN — SSRIs less effective at low weight)
• Refeeding protocol: Start 10 kcal/kg/day (5 if very high risk); supplement phosphate, K⁺, Mg²⁺, thiamine (Pabrinex)

Referral Criteria

• Suspected eating disorder — specialist eating disorder service
• BMI <15 or rapid weight loss — urgent medical assessment
• Medical complications — may need inpatient medical care
• Under 18 — CAMHS eating disorder service
• Treatment under Mental Health Act — if refusing life-saving treatment and meets criteria

• Anorexia nervosa: Standardised mortality ratio 5-6× expected; ~20% develop chronic course; ~50% fully recover
• Bulimia nervosa: Better prognosis; ~50% recovery with CBT; ~30% partial recovery
• Binge eating disorder: Good response to psychological treatment; often comorbid with obesity
• Cause of death in AN: Cardiac arrhythmia (~30%), suicide (~20%), medical complications (~50%)
• Poor prognostic factors: Late onset, binge-purge subtype, comorbid depression, low BMI, longer duration before treatment
• Duration of illness before treatment is the strongest predictor of outcome — early intervention is key

SCOFF Screening Questionnaire

Medical Complications by System