Psychiatry
Gastroenterology
High Evidence

Eating Disorders (Anorexia, Bulimia & BED)

Updated 2026-01-04
5 min read

Eating Disorders

1. Clinical Overview

The Spectrum

  1. Anorexia Nervosa (AN): Restriction of energy intake leading to low body weight. Intense fear of gaining weight. Disturbance in body image.
  2. Bulimia Nervosa (BN): Recurrent binge eating + Compensatory behavior (Purging/Laxatives). Normal or overweight.
  3. Binge Eating Disorder (BED): Binges without compensatory behavior. Associated with obesity.

Mortality

  • Anorexia has the highest mortality rate of any psychiatric disorder.
  • Death from: Cardiac Arrhythmia (Hypokalaemia), Suicide, Infection.

2. Epidemiology

  • Anorexia: 0.5% lifetime. F:M 10:1. Peak onset 15-19 years.
  • Bulimia: 1-2% lifetime. Slightly older onset (18-24).
  • Risk Factors: Female, Perfectionism, Childhood obesity, Family history, Media pressure, Ballet/Athletics.

3. Physical Complications (Systemic Review)

The body shuts down non-essential functions to survive.

Cardiovascular

  • Bradycardia (less than 40 bpm is dangerous).
  • Hypotension (Postural drop).
  • Arrhythmia: Prolonged QTc -> Torsades de Pointes (Sudden Death).
  • Mitral Valve Prolapse.

Gastrointestinal

  • Delayed gastric emptying (bloating).
  • Constipation.
  • Dental Erosion (Bulimia - acid wash).
  • Russell's Sign: Calluses on knuckles from inducing vomiting.
  • Parotid Swelling ("Chipmunk cheeks").

Endocrine

  • Amenorrhoea: HPA axis suppression (Low LH/FSH/Oestrogen).
  • Osteoporosis: Low oestrogen + High Cortisol.
  • Hypothermia (Lanugo hair growth to keep warm).

Musculoskeletal

  • Proximal Myopathy (Squat test failure).

4. Investigations

"MARSIPAN" Assessment (Management of Really Sick Patients with Anorexia Nervosa)

Bloods

  • U&E:
    • Hypokalaemia (Vomiting/Laxatives) -> Cardiac Arrest.
    • Hyponatraemia (Water loading to hide weight).
  • FBC: Pancytopenia (Bone marrow starvation).
  • LFT: Elevated (Starvation hepatitis).
  • Glucose: Hypoglycaemia.

ECG (Mandatory)

  • Look for: Bradycardia, QTc prolongation, T wave inversion.

Bone Density (DEXA)

  • If amenorrhoea > 1 year.

5. Management: Anorexia Nervosa

Setting

  • Most managed as outpatients (Family Therapy).
  • Admission Criteria:
    • BMI less than 13.
    • Weight loss > 1kg/week.
    • HR less than 40, BP less than 90/60.
    • Temp less than 35°C.
    • Suicide risk.

Psychological (NICE NG69)

  1. Family Based Treatment (FBT): "Maudsley Model". Parents take control of re-feeding. Gold standard for adolescents.
  2. CBT-ED: Enhanced CBT for adults. Focus on control/perfectionism.
  3. MANTRA: Maudsley Anorexia Nervosa Treatment for Adults.

Pharmacology

  • No specific drug treats Anorexia.
  • Olanzapine sometimes used for distress/weight gain (weak evidence).
  • SSRIs ineffective at low weight (need tryptophan to work).

6. Management: Bulimia Nervosa

Psychological

  1. Bulimia-nervosa-focused family therapy (FT-BN): Children.
  2. CBT-ED: Adults.

Pharmacology

  • Fluoxetine (High dose 60mg).
    • Evidence base is stronger than in Anorexia. Reduces binge impulse.

7. Refeeding Syndrome

Pathophysiology

  • Starvation = Switch to Fat metabolism. Intracellular Phosphate/Potassium/Magnesium depleted (but serum levels normal due to homeostasis).
  • Refeeding (Carbs) = Insulin surge.
  • Insulin drives Phosphate/K/Mg INTO cells.
  • Serum levels crash.

The Consequence

  • Hypophosphataemia: No ATP. Respiratory failure, Rhabdomyolysis, Seizures, Heart Failure.
  • Hypokalaemia: Arrhythmia.

Prevention (NICE)

  • Start low (10-20 kcal/kg/day). Increase slowly.
  • Supplement: Thiamine (Pabrinex), Phosphate (Sandoz), Potassium.
  • Monitor bloods daily.

Mental Health Act

  • Can you force feed? YES.
  • Anorexia is a mental disorder. Refusing food is a manifestation of the disorder.
  • Can treat under Section 3 (Medical treatment for mental disorder).
  • Caveat: Nasogastric feeding under restraint is a last resort ("high intensity").

9. Clinical Case Study: The "Monster Resource" Viva

Presentation

A 16-year-old female collapses at school. BMI 12.5. HR 38. She admits to running 10km daily and throwing away lunch.

Clinical Decision Points (Viva Style)

Q1: Assessment priority? A: Medical Stabilization.

  • ECG (QTc/Bradycardia).
  • Bloods (K+).
  • Glucose.

Q2: She refuses admission. Can you keep her? A: Yes.

  • She lacks capacity (Clouded by starvation/anorexia voice).
  • Use Mental Health Act (Section 2) if refusal persists. Risk of death is imminent.

Q3: You start feeding. On Day 3 she becomes breathless and confused. Phosphate is 0.3. Diagnosis? A: Refeeding Syndrome.

  • Action: Stop/reduce feed. IV Phosphate/Electrolyte replacement. Cardiac monitor.

Q4: Long term complication to warn about? A: Infertility and Osteoporosis.

  • "If we don't fix this, your bones will break like an 80-year-old's".

10. References (High-Yield List)

  1. NICE NG69 (2017). Eating disorders: recognition and treatment.
  2. MARSIPAN Guidelines (RCPath 2014). Management of Really Sick Patients with Anorexia Nervosa.
  3. Treasure J et al. Eating disorders. Lancet. 2010.
  4. Lock J et al. Randomized clinical trial comparing family-based treatment with adolescent-focused individual therapy for adolescents with anorexia nervosa. Arch Gen Psychiatry. 2010.
  5. Mehanna HM et al. Refeeding syndrome: what it is, and how to prevent and treat it. BMJ. 2008.
  6. Attia E et al. Olanzapine versus placebo for outpatients with anorexia nervosa. Am J Psychiatry. 2019.
  7. Fairburn CG et al. Psychotherapy and bulimia nervosa. Arch Gen Psychiatry. 1993.
  8. Arcelus J et al. Mortality rates in patients with anorexia nervosa and other eating disorders: a meta-analysis of 36 studies. Arch Gen Psychiatry. 2011.

11. Examination Focus (Monster Mode)

Common Exam Questions

  1. "Russell's Sign?" → Calluses on knuckles (Bulimia).
  2. "ECG finding in Anorexia?" → Sinus Bradycardia, QTc prolongation (Electrolyte disturb).
  3. "Refeeding Syndrome marker?" → Hypophosphataemia.
  4. "Drug for Bulimia?" → Fluoxetine 60mg.
  5. "Squat test?" → Proximal myopathy (starvation).

"Do Not Miss" Red Flags

  1. Hypoglycaemia: Can be asymptomatic. Sudden death risk.
  2. Water Loading: Check Sodium. Seizure risk.
  3. Concealed weights: Weigh in underwear. Check pockets.

Examiners' Pearls

  • Lanugo Hair: Fine downy hair on back/arms. The body trying to insulate itself.
  • Sialadenosis: Swollen parolids. Often mistaken for Mumps. It's Bulimia.
  • SCOFF Questionnaire: Screening tool. (Sick, Control, One stone, Fat, Food).

Medical Reviewer: Dr. P. Psych, Consultant Psychiatrist (Jan 2026) Last Updated: 2026-01-04