People with anorexia nervosa have extreme weight loss as a result of very strict dieting. In spite of this, they believe they are fat and are terrified of becoming what is in reality a normal weight or shape. A diagnosis of anorexia nervosa is based on:

• Weight, measured as body mass index (BMI) <17.5 kg/m² due to controlled eating.
• Distorted body image and abnormal attitudes to food and weight.
• Amenorrhoea and often other signs of starvation.

Epidemiology

• Estimated mean yearly incidence is 20 per 100,000 people a year in women, and 2 per 100,000 people a year in men.¹
• Anorexia nervosa affects women more than men (ratio 10:1). But men are more likely to be underdiagnosed, misdiagnosed and under-referred.
• The typical age of onset is during mid-adolescence.
• Family history: 55% concordance in monozygotic and 5% in dizygotic twins.
• People with low self esteem or who are perfectionists are more vulnerable.

Presentation

• The defining clinical features are:
  • Deliberate weight loss with restriction of food intake.
  • Weight below 85% of predicted (body mass index below 17.5 kg/m²).
  • Have a dread of gaining weight and overevaluate their shape and weight.
  • Amenorrhoea for three months or longer (unless they are taking an oral contraceptive).
• Other features include:
  • Physical: includes fatigue, hypothermia, hypotension, slow pulse, peripheral oedema, gaunt face, lanugo hair, scanty pubic hair, arrhythmias. Delay in secondary sexual development if pre-puberty.
  • Symptoms of depression and obsession.
  • Preoccupation with food; enjoyment of cooking for other people.
  • Social withdrawal; few interests.
  • Enhanced weight loss by over-exercise, diuretics, laxatives and self-induced vomiting.

Physical risk

• The Institute of Psychiatry has produced a guide to the assessment of medical risk for eating disorders.³
• The following parameters are a guide to the need for urgent referral and appropriate medical intervention. Risk increases with degree of abnormality and patients may need immediate referral, assessment and treatment:
  • Nutrition: BMI below 14; weight loss more than 0.5 kg per week.
  • Circulation: Systolic BP below 90; diastolic below 70; postural drop greater than 10 mmHg.
  • Squat test: unable to get up without using arms for balance or leverage.
  • Core temperature below 35 degrees.
  • Blood tests: Low potassium, sodium, magnesium or phosphate. Raised urea or liver function tests. Low albumin or glucose.
  • ECG: pulse rate below 50; prolonged QT interval.

Investigations

• An ESR and thyroid function tests are a useful screen for other causes of weight loss.
• Other tests will depend on the individual presentation.
• In patients with eating disorders, frequent testing for FBC, ESR, urea, electrolytes, creatinine, glucose, liver function tests and thyroid function tests is required.

Management⁴

• Mild anorexia nervosa (body mass index above 17 kg/m²) and no significant co-morbidities can be managed in primary care with support and monitoring.
• But if patients don't respond within eight weeks you should make a routine referral to specialist services.
• Refer patients with moderate anorexia nervosa (body mass index 15-17 kg/m²) and no significant co-morbidities non-urgently to specialist services.
• Refer patients with severe anorexia nervosa (body mass index less than 15 kg/m²), rapid weight loss, or evidence of system failure urgently to specialist services, or a medical unit if the physical status of the patient is life threatening.
• Self help (with or without guidance from a therapist) may have some utility as a first step in treatment and may have potential as an alternative to formal therapist-delivered psychological therapy.⁵
• Psychological treatments of anorexia nervosa include cognitive analytic therapy, cognitive behaviour therapy, interpersonal psychotherapy, focal psychodynamic therapy and family interventions focused explicitly on eating disorders.
• Family interventions that directly address the eating disorder should be offered to children and adolescents with anorexia nervosa. Family members, including siblings, should normally be included in the treatment of children and adolescents with eating disorders. Family therapy is one of the few therapies with good evidence of benefit.¹
• There is a very limited evidence base for the pharmacological treatment of anorexia nervosa.⁶ Medication for co-morbid conditions such as depressive or obsessive-compulsive features should be used with caution as they may resolve with weight gain alone, and side effects of drug treatment (in particular, cardiac side effects) should be carefully considered because of the compromised cardiovascular function of many people with anorexia nervosa.
• Managing weight gain:
  • In most patients: an average weekly weight gain of 0.5-1 kg in inpatient settings and 0.5 kg in outpatient settings should be an aim of treatment (this requires about 3500 to 7000 extra calories a week).
  • Regular physical monitoring.
  • Multi-vitamin and mineral supplements.
• Managing risk:
  • Risk should be very closely monitored.
  • If all efforts of discussion and concordance break down and essential treatment is refused, then very occasionally there is a need to use the Mental Health Act, or the right of those with parental responsibility to override the young person's refusal, or even legal advice may be needed in order to consider proceedings under the Children Act 1989.

Complications

• Hypokalaemia: common and may cause fatal arrhythmias
• Hypotension
• Anaemia
• Cardiac failure
• Hypoglycaemia
• Osteoporosis: restoring the patient's weight is the best treatment. The value of hormone replacement therapy is not clear, and may cause the epiphyses to fuse prematurely.
• Infections
• Acute renal failure
• Alcoholism (chronic illness)

Prognosis

• Anorexia nervosa has a variable prognosis.
• About four out of ten people with fully established anorexia nervosa make a full recovery.
• Mortality rate in long-term studies is 15-20%. Most deaths result from suicide or direct medical complications.
• Poor prognosis is predicted by a long duration of illness prior to presentation and onset in adulthood.

Document references

1. Eating disorders, NICE (2004); Core interventions in the treatment and management of anorexia nervosa, bulimia nervosa and related eating disorders
2. Wentz E, Gillberg IC, Anckarsater H, et al; Adolescent-onset anorexia nervosa: 18-year outcome. Br J Psychiatry. 2009 Feb;194(2):168-74. [abstract]
3. Institute of Psychiatry; A Guide to the Medical Risk Assessment for Eating Disorders.
4. Guidelines for the nutritional management of anorexia nervosa, Royal College of Psychiatrists (2005)
5. Perkins SJ, Murphy R, Schmidt U, et al; Self-help and guided self-help for eating disorders. Cochrane Database Syst Rev. 2006 Jul 19;3:CD004191. [abstract]
6. Claudino AM, Hay P, Lima MS, et al; Antidepressants for anorexia nervosa. Cochrane Database Syst Rev. 2006 Jan 25;(1):CD004365. [abstract]
7. Morris J, Twaddle S; Anorexia nervosa. BMJ. 2007 Apr 28;334(7599):894-8.

Internet and further reading

• Eating disorders, Clinical Knowledge Summaries (October 2009)
• The National Centre for Eating Disorders; Counselling, Self Help, Professional Training and Support.
• Eating Disorders Association; For patients and professionals.
• Royal College of Psychiatrists; Eating Disorders.
• Eating Disorders Research, Institute of Psychiatry; Resources for health professionals.

Acknowledgements