Anorexia Nervosa
Summary
Anorexia nervosa (AN) is a serious eating disorder characterised by persistent restriction of energy intake leading to significantly low body weight, an intense fear of gaining weight or becoming fat, and a disturbed perception of body weight or shape. It has the highest mortality rate of any psychiatric disorder (5-10% over 10 years), primarily from medical complications and suicide. Treatment involves nutritional rehabilitation, psychological therapy (family-based therapy for adolescents, CBT-ED for adults), and close medical monitoring. Refeeding syndrome is a dangerous complication requiring careful management.
Key Facts
- Definition: Restriction of energy intake → significantly low body weight + fear of weight gain + body image disturbance
- Prevalence: 0.5-1% (females); 0.1% (males)
- Mortality: Highest of any psychiatric disorder — 5-10% over 10 years
- Subtypes: Restricting type, Binge-eating/Purging type
- Severity (BMI): Mild ≥17, Moderate 16-16.99, Severe 15-15.99, Extreme <15
Clinical Pearls
"Refeeding Syndrome Kills": When restarting nutrition in malnourished patients, monitor phosphate, potassium, magnesium daily. Supplement thiamine before feeding.
"SUSS Criteria": Signs of medical instability: Symptomatic hypoglycaemia, Unreliable fluid/nutrition intake, Severe bradycardia (<40 bpm), Symptomatic hypotension.
"BMI Can Be Deceptive": Patients with rapid weight loss are at high risk regardless of absolute BMI.
Why This Matters Clinically
AN is a life-threatening condition requiring a multidisciplinary approach. Medical complications are common and can be fatal. Early intervention improves outcomes, but many patients experience a chronic course.
Prevalence
| Measure | Value |
|---|---|
| Lifetime Prevalence (F) | 0.5-1% |
| Lifetime Prevalence (M) | 0.1% |
| Peak Age of Onset | 14-18 years |
| Female:Male | 10:1 |
Risk Factors
| Factor | Details |
|---|---|
| Genetics | 50-80% heritability |
| Personality | Perfectionism, obsessionality, low self-esteem |
| Trauma | Childhood abuse/neglect |
| Occupational | Ballet, modelling, athletics, gymnastics |
| Family | Diet culture, parental eating disorders |
Starvation Effects
| System | Effects |
|---|---|
| Cardiac | Bradycardia, hypotension, cardiomyopathy, arrhythmias |
| Endocrine | Amenorrhoea (↓GnRH), ↓T3, ↑cortisol |
| Bone | Osteoporosis (early, may be irreversible) |
| GI | Delayed gastric emptying, constipation |
| Haematological | Pancytopenia |
| Neurological | Brain atrophy (reversible), peripheral neuropathy |
| Dermatological | Lanugo, dry skin, hair loss |
Symptoms
Physical Signs
| Sign | Details |
|---|---|
| Lanugo | Fine downy hair on body |
| Bradycardia | HR <60 (severe <40) |
| Hypotension | Postural drop |
| Hypothermia | Core temp <36°C |
| Peripheral Oedema | From hypoalbuminaemia |
| Russell's Sign | Calluses on knuckles (purging) |
| Dental Erosion | Purging type |
| Parotid Enlargement | Purging type |
Red Flags
[!CAUTION] Medical Emergency Indicators:
- HR <40 bpm
- BP <90 systolic
- Temperature <35°C
- K+ <3.0 mmol/L
- Symptomatic hypoglycaemia
- QTc prolongation
Physical
- Weight, height, BMI
- Vitals: HR, BP (lying and standing), temperature
- Signs of malnutrition
- SUSS test (Sit Up, Squat, Stand)
Mental State
| Domain | Findings |
|---|---|
| Appearance | Emaciated, cold, layered clothing |
| Mood | Low, anxious |
| Thought Content | Overvalued ideas about weight/shape |
| Insight | Variable (often impaired) |
| Test | Purpose |
|---|---|
| FBC | Pancytopenia |
| U&E | K+, Na+, renal function |
| Phosphate, Mg, Ca | Refeeding risk |
| Glucose | Hypoglycaemia |
| LFTs | Liver dysfunction |
| TFTs | Sick euthyroid |
| ECG | Bradycardia, QTc |
| DEXA | Osteoporosis |
Medical Stabilisation
- Refeeding syndrome prevention
- Electrolyte monitoring and correction
- Gradual caloric increase
Psychological
| Population | Therapy |
|---|---|
| Adolescents | Family Therapy for AN (FT-AN) |
| Adults | CBT-ED, MANTRA, or SSCM |
Pharmacology
- No specific medication for AN
- SSRIs for comorbid depression (after weight restoration)
| Complication | Notes |
|---|---|
| Cardiac | Arrhythmias, cardiomyopathy |
| Refeeding Syndrome | Hypophosphataemia, cardiac failure |
| Osteoporosis | Early and potentially irreversible |
| Infertility | From hypothalamic suppression |
| Suicide | Significant cause of mortality |
| Death | 5-10% mortality over 10 years |
Course
| Outcome | Rate |
|---|---|
| Full Recovery | ~50% |
| Partial Recovery | ~30% |
| Chronic Course | ~20% |
| Mortality | 5-10% over 10 years |
Prognostic Factors
| Good | Poor |
|---|---|
| Shorter duration of illness | Longer duration |
| Younger age at onset | Older age at onset |
| Higher BMI at presentation | Very low BMI |
| Good family support | Comorbid psychiatric illness |
Key Guidelines
-
NICE NG69: Eating disorders (2017)
-
MARSIPAN Guidelines (Royal Colleges, 2022)
Evidence Strength
| Intervention | Level | Notes |
|---|---|---|
| FT-AN for adolescents | 1a | Best evidence |
| CBT-ED for adults | 1b | Recommended |
What is Anorexia Nervosa?
Anorexia nervosa is a serious eating disorder where you eat very little to lose weight, even when already underweight. It's not about vanity — it's a mental health condition that affects how you see your body.
What are the symptoms?
- Severe weight loss
- Intense fear of gaining weight
- Seeing yourself as overweight when you're not
- Missing periods (in women)
- Feeling cold, tired, dizzy
- Hiding eating habits
How is it treated?
- Medical care: Restoring weight safely, monitoring heart and blood tests
- Therapy: Talking therapies help change thoughts and behaviours about food and weight
- For teenagers: Family-based therapy
- For adults: CBT for eating disorders
- Support: Dietitian input, regular monitoring
What to expect
- Recovery is possible, but often takes time
- The earlier treatment starts, the better the outcome
- Many people make a full recovery
Primary Guidelines
-
National Institute for Health and Care Excellence. Eating disorders: recognition and treatment (NG69). 2017. nice.org.uk/guidance/ng69
-
Royal College of Psychiatrists, et al. MARSIPAN: Management of Really Sick Patients with Anorexia Nervosa. 2022. rcpsych.ac.uk
Further Resources
- Beat Eating Disorders: beateatingdisorders.org.uk
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Anorexia nervosa is a medical emergency — seek help immediately if concerned.