Anorexia Nervosa

oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

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.

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  • 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). However, 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.
  • It is not known whether a neurobiological vulnerability predisposes to anorexia nervosa or if this is associated with maintenance of symptoms once the illness develops. Further research is needed to examine the degree to which abnormalities are a consequence of starvation or are caused by an anorexia nervosa endophenotype.[2]
  • Cultural, social, and interpersonal elements can trigger onset and changes in neural networks can sustain the illness.[3]
  • The defining clinical features are:
    • Deliberate weight loss with restriction of food intake.
    • Weight below 85% of predicted (BMI below 17.5 kg/m2).
    • Having a dread of gaining weight, and over-evaluating 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.

Early diagnosis[1]

  • Detecting the problem early improves prognosis.[4] Furthermore, early admission may also improve prognosis.[4]
  • Target groups for screening should include young women with low BMI, patients consulting with weight concerns who are not overweight, women with menstrual disturbances or amenorrhoea, patients with gastrointestinal symptoms, patients with physical signs of starvation or repeated vomiting, and children with poor growth.
  • One or two simple screening questions can be used. For example: 'Do you think you have an eating problem?' or 'Do you worry excessively about your weight?'. The SCOFF questionnaire (below) is a useful screening tool. Two or more positive answers should prompt a more detailed history:
    • Do you ever make yourself S ick because you feel uncomfortably full?
    • Do you worry you have lost C ontrol over how much you eat?
    • Have you recently lost more than O ne stone in a three-month period?
    • Do you believe yourself to be F at when others say you are too thin?
    • Would you say that F ood dominates your life?
  • The Section of Eating Disorders at the Institute of Psychiatry has produced a guide to the assessment of medical risk for eating disorders.[5]
  • 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 BP below 70; postural drop greater than 10 mm Hg.
    • Squat test: unable to get up without using arms for balance or leverage.
    • Core temperature below 35°C.
    • Blood tests: low potassium, sodium, magnesium or phosphate. Raised urea or LFTs. Low albumin or glucose.
    • ECG: pulse rate below 50; prolonged QT interval.
  • An ESR and TFTs 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, U&Es, creatinine, glucose, LFTs and TFTs is required.
  • A dual-energy X-ray absorptiometry (DEXA) scan may be performed in those who have had amenorrhoea for more than six months.
  • An ECG may show bradycardia or a prolonged QT interval in those with more severe anorexia.
  • Mild anorexia nervosa (BMI above 17 kg/m2) and no significant comorbidities can be managed in primary care with support and monitoring.
  • However, if patients don't respond within eight weeks, you should make a routine referral to specialist services.
  • Refer patients with moderate anorexia nervosa (BMI 14-17 kg/m2) and no significant comorbidities non-urgently to specialist services.
  • Refer patients with severe anorexia nervosa (BMI less than 14 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.[7]
  • Psychological treatments of anorexia nervosa include cognitive analytic therapy, cognitive behavioural 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.
  • There is some evidence to suggest that family therapy may be effective compared to treatment as usual in the short term. However, a recent Cochrane review showed that there appears to be little advantage of family therapy over other psychological interventions. [8]
  • There is a very limited evidence base for the pharmacological treatment of anorexia nervosa.[9]
  • Medication for comorbid 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.
  • Risedronate has been shown to increase spinal bone mineral density when given for one year.[10]
  • 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 3,500 to 7,000 extra calories a week).
    • Regular physical monitoring.
    • Multivitamin 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.
Tips for non-specialists:[11]
  • Recovery takes years (not weeks or months). Patients must accept attainment of normal weight (re-feeding alone has a higher relapse rate).
  • Monitor by weighing (but this needs to be managed skilfully as it can cause difficulties).
  • Risk is affected by many factors, not just BMI.
  • Substance misuse carries a high risk, particularly alcohol misuse. Deliberate overdoses, or misuse of prescribed drugs (especially insulin) also increase risk.
  • Weight fluctuations and binge-purge methods (rather than pure restriction) increase risk.
  • Depression, anxiety, and family arguments are probably secondary to the disorder (not underlying causes). It is therefore important to treat the anorexia first.
  • Medication has little benefit in anorexia (there is high risk of dangerous side-effects in malnourished patients).
  • Try to involve the family and encourage a calm but firm and assertive approach to care.
  • Hypokalaemia: common and may cause fatal arrhythmias.
  • Hypotension.
  • Anaemia.
  • Cardiac failure.
  • Hypoglycaemia.
  • Osteoporosis: restoring the patient's weight is the best treatment. Bone loss may never recover completely even once weight is restored.
  • Infections.
  • Acute renal failure.
  • Alcoholism in some patients.
  • Anorexia nervosa has a variable prognosis.
  • Anorexia nervosa has the highest mortality of all psychiatric conditions.
  • 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.

Further reading & references

  1. Eating disorders - core interventions in the treatment and management of anorexia nervosa, bulimia nervosa and related eating disorders; NICE (2004)
  2. Hay PJ, Sachdev P; Brain dysfunction in anorexia nervosa: cause or consequence of under-nutrition? Curr Opin Psychiatry. 2011 May;24(3):251-6.
  3. Treasure J, Claudino AM, Zucker N; Eating disorders. Lancet. 2010 Feb 13;375(9714):583-93.
  4. Wentz E, Gillberg IC, Anckarsater H, et al; Adolescent-onset anorexia nervosa: 18-year outcome. Br J Psychiatry. 2009 Feb;194(2):168-74.
  5. A Guide to the Medical Risk Assessment for Eating Disorders - Professor Janet Treasure, King's College London, 2009
  6. Guidelines for the nutritional management of anorexia nervosa, Royal College of Psychiatrists (2005)
  7. 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.
  8. Fisher CA, Hetrick SE, Rushford N; Family therapy for anorexia nervosa. Cochrane Database Syst Rev. 2010 Apr 14;(4):CD004780.
  9. Claudino AM, Hay P, Lima MS, et al; Antidepressants for anorexia nervosa. Cochrane Database Syst Rev. 2006 Jan 25;(1):CD004365.
  10. Miller KK, Meenaghan E, Lawson EA, et al; Effects of risedronate and low-dose transdermal testosterone on bone mineral J Clin Endocrinol Metab. 2011 Jul;96(7):2081-8. Epub 2011 Apr 27.
  11. Morris J, Twaddle S; Anorexia nervosa. BMJ. 2007 Apr 28;334(7599):894-8.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Colin Tidy
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
1806 (v24)
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