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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Significantly low body weight (BMI <17.5 kg/m²) maintained through dietary restriction, excessive exercise, purging, or laxative use
- Intense fear of gaining weight + distorted body image (perceives self as overweight despite being underweight)
- Two subtypes: restricting type and binge-purge type
- Highest mortality of ANY psychiatric disorder (~5–20% over 20 years) — death from malnutrition, cardiac arrhythmia, or suicide
- First-line for children/adolescents: family-based therapy (FBT/Maudsley approach). Adults: individual eating-disorder-focused CBT (CBT-ED) or MANTRA
- Refeeding syndrome risk: hypophosphataemia, hypokalaemia, hypomagnesaemia when reintroducing nutrition in severely malnourished patients
Overview
Anorexia nervosa is a serious eating disorder characterised by restriction of energy intake leading to significantly low body weight (BMI <17.5 kg/m² or <85% expected weight), an intense fear of weight gain, and persistent disturbance in body image. Two subtypes exist: restricting type (weight loss through dieting, fasting, and/or excessive exercise) and binge-eating/purging type (episodes of binge eating and/or purging — self-induced vomiting, laxatives, diuretics). Anorexia nervosa has the highest mortality rate of any psychiatric disorder, with deaths resulting from medical complications of starvation (cardiac arrhythmia, renal failure) and suicide. It is classified in ICD-11 as a feeding and eating disorder.
Epidemiology
Anorexia nervosa affects approximately 0.3–1% of young women in the UK. The female:male ratio is approximately 10:1, although male cases are increasingly recognised. Typical onset is in adolescence (14–19 years). Risk factors include female sex, family history of eating disorders, perfectionism, high academic achievement, occupations with weight focus (ballet, modelling, athletics), childhood adversity, and social media exposure. It is more common in higher socioeconomic groups. Mortality rate is approximately 5% per decade of illness, making it the deadliest psychiatric condition.
Clinical Features
Symptoms
Severe dietary restriction — detailed food rules, calorie counting, avoiding food groups
Fear of weight gain and distorted body image — perceives self as overweight despite emaciation
Excessive exercise — compulsive, continued despite illness or injury
Purging behaviours: self-induced vomiting, laxative/diuretic misuse
Amenorrhoea (in females) or loss of libido (in males) — secondary to hypothalamic suppression
Cold intolerance, fatigue, dizziness, syncope
Constipation, bloating, abdominal pain
Suicidal ideation — significant risk factor
Signs
Significantly low BMI (<17.5 kg/m²). Severe: <15. Extreme: <13
Lanugo hair (fine downy hair on face, arms, trunk)
Bradycardia, hypotension, hypothermia
Peripheral oedema (hypoalbuminaemia)
Russell sign: calluses on knuckles from self-induced vomiting
Parotid gland enlargement (if purging)
Dental erosion (from vomiting — palatal surface of upper teeth)
Investigations
First-line
BMI calculationBMI <17.5 kg/m² = anorexia. Severe: <15. Extreme: <13. Also assess rate and extent of weight loss
BloodsFBC (leucopenia, anaemia), U&Es (hypokalaemia from purging), LFTs, glucose, calcium, magnesium, PHOSPHATE (refeeding risk), albumin
ECGBradycardia, prolonged QTc, arrhythmia (hypokalaemia-related). Mandatory if BMI <15 or rapid weight loss
Second-line
TFTsLow T3 (sick euthyroid syndrome) — adaptive response to starvation
Hormonal assessmentLow oestrogen/testosterone, low LH/FSH (hypothalamic suppression), raised cortisol
DEXA scanBone mineral density — if amenorrhoea >6–12 months or history of fractures. High risk of osteoporosis
Specialist
EchocardiogramIf severe bradycardia or cardiovascular compromise — assess for mitral valve prolapse, pericardial effusion
1
Children and adolescents
- First-line: anorexia nervosa-focused family therapy (FT-AN/Maudsley approach) — family manages refeeding
- If family therapy declined/ineffective: individual eating-disorder-focused CBT (CBT-ED)
- Aim for weight restoration with structured meal support
2
Adults
- First-line: individual eating-disorder-focused CBT (CBT-ED), MANTRA (Maudsley Anorexia Nervosa Treatment for Adults), or SSCM (specialist supportive clinical management)
- Weight restoration target: BMI ≥20 kg/m² (or above 95th centile in children)
- Multidisciplinary approach: psychiatrist, dietitian, psychologist, GP
3
Medical stabilisation and refeeding
- Admit if: BMI <13, rapid weight loss, cardiovascular compromise (HR <40, QTc prolonged), severe electrolyte disturbance, acute medical complication
- Refeeding syndrome prevention: start calories low (10–20 kcal/kg/day in severe cases), increase gradually
- Monitor phosphate, potassium, magnesium DAILY during refeeding. Supplement prophylactic thiamine (Pabrinex) and phosphate
- Refeeding syndrome: hypophosphataemia → cardiac failure, arrhythmia, confusion, seizures. Life-threatening
4
Pharmacotherapy
- No drug treatment for anorexia nervosa itself (NICE NG69)
- Treat comorbid depression/anxiety AFTER weight restoration — SSRIs less effective in malnourished state
- Do NOT offer appetite stimulants or nutritional supplements as sole treatment
Complications
- Cardiac: Bradycardia, arrhythmia (hypokalaemia, hypomagnesaemia), cardiac failure, sudden death
- Refeeding syndrome: Hypophosphataemia, hypokalaemia, hypomagnesaemia, fluid overload — life-threatening in early refeeding
- Osteoporosis: Oestrogen deficiency + malnutrition → reduced bone mineral density. May be irreversible
- Endocrine: Amenorrhoea, infertility, growth retardation (if onset pre-puberty), hypothermia
- Renal: AKI from dehydration, chronic kidney damage from prolonged malnutrition
- Suicide: Second leading cause of death (after medical complications) in anorexia nervosa
UKMLA Exam Tips
- 1Anorexia = BMI <17.5 + fear of weight gain + body image distortion. Highest mortality of ANY psychiatric disorder
- 2Refeeding syndrome: hypoPHOSPHATAEMIA is the hallmark. Monitor phosphate, K⁺, Mg²⁺ daily. Start feeds slowly, give thiamine
- 3Family-based therapy (Maudsley approach) is first-line for children/adolescents. CBT-ED or MANTRA for adults
- 4Russell sign (knuckle calluses) and dental erosion (palatal surface) = evidence of self-induced vomiting
- 5Lanugo hair, bradycardia, hypothermia, amenorrhoea = classic physical signs of starvation
- 6No medication is recommended for anorexia nervosa itself. Treat comorbidities AFTER weight restoration
- 7Sick euthyroid (low T3) is adaptive — do NOT treat with levothyroxine. It normalises with weight restoration
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