Anorexia Nervosa

Professional Reference 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 maintain a low body weight as a result of a preoccupation with weight, construed as either a fear of fatness or a pursuit of thinness[1]. 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 features including low body weight, rapid weight loss, weight loss measures (particularly extreme dieting), and psychological features (usually including distorted body image), along with physical and endocrine sequelae. Anorexia nervosa can cause widespread physical and psychological morbidity and it can result in death.

  • Estimated mean yearly incidence of anorexia nervosa is 0.4 in 1,000 per year in females, and 9 in 1,000 females will experience the condition at some time in their lives.
  • 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 early adolescence to mid-adolescence.
  • Although not common in the general population, eating disorders as a whole are thought to be the third most common chronic illness in adolescent females (after asthma and obesity)[2].

The aetiology of anorexia nervosa is thought to be multifactorial, involving biological, psychological, developmental and sociocultural factors[3]. 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[4]. It may be that cultural, social and interpersonal elements can trigger onset, and changes in neural networks can sustain the illness[5].

The main risk factors are thought to be:

  • Female gender.
  • Age.
  • Living in a Western society.
  • Family history of eating disorder, depression or substance misuse. Results of twin studies are inconclusive, with some suggesting a strong link, and others none.
  • Premorbid experiences. These include:
    • Sexual abuse.
    • Dieting behaviour within family or personal experience.
    • Occupational or recreational pressure to be slim (dancers, gymnasts, jockeys, models).
    • Onset of puberty.
    • Criticism or perceived criticism about weight or eating behaviour.
  • Personal characteristics:
    • Perfectionism.
    • Low self-esteem.
    • Obsessional traits.
    • Premorbid obesity.
    • Early menarche.
    • Difficulty with resolving conflict.
    • Anxiety.
    • Emotionally unstable personality disorder (formerly borderline personality disorder).

Suspicion and diagnosis are based on history, suggestive clinical features and often concerns raised by a relative or friend. No single measure such as body mass index (BMI) can be used for either diagnosis or a decision about the need for treatment.

Clinical features include:

  • Refusal to maintain a normal body weight for age and height.
  • Weight below 85% of predicted. This means in adults a BMI below 17.5 kg/m2. For those under 18 years of age, BMI centile charts should be used. In young people there may be a lack of appropriate weight gain, rather than weight loss.
  • Dieting or restrictive eating practices. Friends or family may report a change in eating behaviour.
  • Rapid weight loss.
  • Having a dread of gaining weight.
  • Disturbance in the way weight or shape is experienced, resulting in over-evaluation of size. Disproportion in concern about weight or shape.
  • Denial of the problem.
  • Lack of desire for intervention, or resistance to it.
  • Social withdrawal; few interests.
  • Enhanced weight loss by over-exercise, diuretics, laxatives and self-induced vomiting.
  • Problems managing pre-existing chronic diseases which involve dietary control, such as diabetes or coeliac disease.

Other physical features include:

  • In women, amenorrhoea for three months or longer. This was part of the defining criteria in the Diagnostic and Statistical Manual of Mental Disorders fourth edition (DSM-IV) classification, but was removed as being essential for a definition with the advent of DSM-5 in 2013.
  • Gastrointestinal symptoms are common, such as constipation, a feeling of fullness after meals, dysphagia and abdominal pains, and may hinder diagnosis and treatment[8].
  • Symptoms such as fatigue, fainting, dizziness and intolerance of cold.
  • Delay in secondary sexual development if pre-puberty.

Examination[1]

Examination should include:

  • Height, weight and BMI.
  • Core temperature.
  • Peripheral examination - circulation, oedema.
  • Cardiovascular examination - pulse, blood pressure, check for postural hypotension.
  • Testing of muscle power by using:
    • Sit up test - lay the person flat and ask them to sit up without using their hands.
    • Squat test - ask the person to squat and then stand up without using their hands.

Examination can be normal but findings could include bradycardia, hypotension, peripheral oedema, gaunt face, lanugo hair, scanty pubic hair, and acrocyanosis (hands or feet are red or purple).

  • An ESR and TFTs are useful screens for other causes of weight loss.
  • Other tests will depend on the individual presentation.
  • U&Es should be checked in all those with behaviours such as vomiting, taking laxatives or diuretics or water loading.
  • In patients with eating disorders and BMI below 15, a history of purging or high risk markers, frequent testing for FBC, ESR, U&Es, creatinine, glucose, LFTs and TFTs is required.[9]
  • Consider a dual-energy X-ray absorptiometry (DXA) scan after a year of being underweight in those below 18 years of age (earlier if fractures or bone pain) and after two years in adults. Consider ongoing monitoring with DXA scans if they remain underweight, but no more often than every year.
  • An ECG may show bradycardia or a prolonged QT interval in those with more severe anorexia.

The Management of Really Sick Patients with Anorexia Nervosa (MARSIPAN and MARSIPAN Junior) documents from the Royal Colleges of Psychiatrists, Physicians and Pathologists set out a risk assessment framework[10, 11].

Adults

In those aged 18 years or over, the following parameters suggest severe anorexia, and 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 of 13-15 conveys medium risk; a BMI <13 is high risk. Note that BMI alone is not an adequate marker of  medical risk.
  • Rate of weight loss: more than 0.5 kg per week[9].
  • Pulse rate: below 40 beats per minute.
  • Blood pressure (BP): systolic BP below 90 mm Hg; diastolic BP below 70 mm Hg; postural drop greater than 10 mm Hg[9].
  • Squat test: unable to get up from squatting or lying down without using arms for balance or leverage.
  • Core temperature below 35°C.
  • Blood tests: low potassium, sodium, magnesium or phosphate. Raised urea, creatinine or transaminases. Low albumin or glucose.
  • ECG: prolonged QT interval, T-wave changes, bradycardia.

Under-18s

In children and young people the risk parameters need adjustment for age and gender. Physiological measurements such as pulse and blood pressure differ from adults and by age, and BMI alone is an inadequate measure. MARSIPAN guidelines advocate using percentage BMI, which is measured as BMI/median BMI for age and gender x 100. Measuring this requires checking standard centile charts for the median BMI[12].

Signs of moderate and severe risk, suggesting the need for urgent or immediate referral include:

  • BMI: medium risk is 70-80% of median BMI (0.4th to 2nd centile) and high risk is <70% (below the 0.2nd centile).
  • Rate of weight loss: medium risk is suggested by recent loss of weight of 500-999 g per week for two consecutive weeks; high risk is 1 kg or more over the same time frame.
  • Pulse rate: medium risk if the pulse rate whilst awake is below 50 beats per minute; high risk below 40 beats per minute.
  • Blood pressures: figures  are dependent on age and gender but below the 2nd centile confers medium risk and below the 0.4th centile high risk.
  • Cardiovascular symptoms: a history of syncope and/or postural drops in blood pressure suggests higher risk.
  • ECG: an increase in the QT interval of 460 ms for girls or 400 ms for boys suggests medium or high risk, particularly in the presence of other rate or rhythm change.
  • Core temperature: <36°C suggests medium risk; <35.5°C high risk.
  • Blood tests: low potassium, sodium, calcium, phosphate, albumin or glucose.
  • Behaviour: severe restriction of calorie intake, moderate to high levels of excessive exercise, fluid restriction, vomiting, purging, poor insight, violent rebellion against parental input, suicidal behaviour and self-harm.
  • Squat test: unable to get up from a lying down position or from squatting without using arms for balance or leverage.

The National Institute for Health and Care Excellence (NICE) recommends that if an eating disorder is suspected, immediate referral be made to a community-based, age-appropriate eating disorder service for further assessment or treatment. The role of the GP is early detection, risk assessment, initial coordination of care, and sharing of ongoing monitoring. Latest guidelines stress the importance of early referral. Helping people with anorexia to reach a healthy body weight or BMI for their age is the key goal. The weight gain is central and is necessary to support any other treatments or changes which may be required in management of the condition.

Management for those under the age of 18 years[13]

Anorexia-nervosa-focused family therapy (FT-AN) for children and young people is currently considered first-line treatment for children and adolescents. This typically involves 18-20 sessions over a year and consists of three phases. It makes the role of the family key in the individual's recovery and gives control of the young person's eating in the first phase to the parents or carers. This allows individual tailoring of diets and eating regimes within the normal context of the young person. No blame should be attributed to either the person or their family. In the second phase, once weight has been restored, the person with anorexia is encouraged to take back some independence in managing their eating habits, and in the final phase planning is made to maintain recovery and prevent relapse. There is evidence for efficacy of this treatment.

Individual cognitive behavioural therapy (CBT) or adolescent-focused psychotherapy are alternatives if family therapy is inappropriate or ineffective.

Management for adults

Psychological treatment options for adults include:

  • Individual eating-disorder-focused cognitive behavioural therapy (CBT-ED). This typically involves 40 sessions over 40 weeks, starting more often than once per week.
  • Maudsley Anorexia Nervosa Treatment for Adults (MANTRA). This usually involves 20 sessions, weekly for the first ten weeks, then depending on response.
  • Specialist supportive clinical management (SSCM). This also involves 20 or more weekly sessions with a specialist practitioner.

If one of these options is ineffective or inappropriate, the others should be tried. An alternative is eating-disorder-focused focal psychodynamic therapy (FPT). A 2015 Cochrane review failed to find enough evidence to recommend one type of therapy over another and advised that larger trials are needed[14].

Management of physical complications

  • Monitoring of U&Es and regular ECGs may be required in severe cases.
  • Oral supplementation may be required to correct abnormal electrolyte balance, or IV if severe.
  • Advise regular assessment by a dentist if the person is vomiting regularly.
  • Seek specialist advice if reduced bone mineral density is diagnosed on DXA scan. Oestrogen treatment is not advised routinely for females with anorexia by NICE, but may be considered for girls aged 13-17 years who have long-term low body weight and low bone mineral density with a bone age over 15, and in physiological dosage in those with delayed puberty and a bone age under 15. Bisphosphonates may be useful in adults.

Management of those who are severely ill[10, 11]

Urgent admission may be required if there is:

  • Electrolyte imbalance or hypoglycaemia.
  • Severe malnutrition.
  • Severe dehydration.
  • Evidence of incipient organ failure.
  • Bradycardia (below 40 beats per minute) or a prolonged QT interval on the ECG.
  • Very low BMI. Levels of risk are detailed above. BMI alone is not usually enough as a measure of high risk and other factors should be taken into consideration.
  • Rapid weight loss (eg, more than 1 kg per week for more than two consecutive weeks).
  • Need for medical stabilisation and refeeding.
  • Inability or incapacity of parents or carers to provide the support needed.
  • Significant suicide risk.

Admission is ideally to a specialist eating disorder unit with expertise to avoid deaths particularly from under-feeding or refeeding syndrome. Guidelines for safe refeeding exist as the MARSIPAN and Junior MARSIPAN documents. Where admission to a medical unit is required, staff need to be aware that these patients are potentially at very high risk, and there will need to be liaison between medical and psychiatric specialists. In some cases admission under the Children Act 1989 or Section 3 of the Mental Health Act may be required.

A clear plan and objectives are needed for treatment and the future for community follow-up after discharge, developed in collaboration with the person with anorexia and their family.

Other considerations for the management of anorexia nervosa

  • Age-appropriate multivitamin-and-mineral supplements should be advised as long as diet is inadequate to provide all necessary nutrients.
  • Dietary advice should be given as part of the multidisciplinary specialist approach.
  • Medication is not advised as the sole treatment for anorexia.
  • Advise avoidance of excessive exercise.
  • There is no evidence for efficacy of physical therapy options such as transcranial magnetic stimulation, acupuncture, weight training, yoga or warming therapy.
  • Collaboration between specialists may be needed where there is comorbid physical or mental illness.
  • 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).
  • Anorexia nervosa has a variable prognosis.
  • Anorexia nervosa has the highest mortality of all psychiatric conditions. This is due to medical complications, and the increased risk of suicide.
  • Approximately 50% of those with anorexia nervosa make a full recovery. 33% improve and 20% have a chronic eating disorder. Where onset is in adolescence, the recovery rate is thought to be higher at 70-80% or more[15].
  • Relapse is common but estimates of relapse rates vary due to non-consistent definitions of relapse. There is said to be a more than 50% relapse rate within a year of successful inpatient treatment[16].
  • Mortality rate is estimated to be 2.8% over an 11-year follow-up. Long-term follow-up studies put this figure as high as 18%[16].
  • Poor prognosis is predicted by a long duration of illness prior to presentation, the need for hospitalisation and onset in adulthood[5, 15].
  • There is a high risk of comorbid or subsequent psychiatric conditions, such as anxiety disorders, obsessive-compulsive disorder (OCD), depression and substance abuse.
  • Early detection may improve prognosis[7].

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  • Costa MB, Melnik T; Effectiveness of psychosocial interventions in eating disorders: an overview of Cochrane systematic reviews. Einstein (Sao Paulo). 2016 Apr-Jun 14(2):235-77. doi: 10.1590/S1679-45082016RW3120.
  1. Eating disorders; NICE CKS, October 2014 (UK access only)
  2. Herpertz-Dahlmann B; Adolescent eating disorders: update on definitions, symptomatology, epidemiology, and comorbidity. Child Adolesc Psychiatr Clin N Am. 2015 Jan 24(1):177-96. doi: 10.1016/j.chc.2014.08.003. Epub 2014 Oct 7.
  3. Rikani AA, Choudhry Z, Choudhry AM, et al; A critique of the literature on etiology of eating disorders. Ann Neurosci. 2013 Oct 20(4):157-61. doi: 10.5214/ans.0972.7531.200409.
  4. Hay PJ, Sachdev P; Brain dysfunction in anorexia nervosa: cause or consequence of under-nutrition? Curr Opin Psychiatry. 2011 May 24(3):251-6.
  5. Treasure J, Claudino AM, Zucker N; Eating disorders. Lancet. 2010 Feb 13 375(9714):583-93.
  6. Eating disorders: recognition and treatment; NICE Guideline (May 2017)
  7. Yeo M, Hughes E; Eating disorders - early identification in general practice. Aust Fam Physician. 2011 Mar 40(3):108-11.
  8. Malczyk Z, Oswiecimska JM; Gastrointestinal complications and refeeding guidelines in patients with anorexia nervosa. Psychiatr Pol. 2017 Apr 30 51(2):219-229. doi: 10.12740/PP/65274. Epub 2017 Apr 30.
  9. Professor Janet Treasure; A Guide to the Medical Risk Assessment for Eating Disorders, King's College London, 2009
  10. MARSIPAN - The management of really sick patients with anorexia nervosa; Royal College of Psychiatrists. 2nd Edition October 2014
  11. Junior MARSIPAN - management of really sick patients under 18 with anorexia nervosa; Royal College of Psychiatrists (Jan 2012)
  12. Body Mass Index (BMI) charts for girls and boys age 2-18; Royal College of Paediatrics and Child Health and Dept of Health.
  13. Rienecke RD; Family-based treatment of eating disorders in adolescents: current insights. Adolesc Health Med Ther. 2017 Jun 1 8:69-79. doi: 10.2147/AHMT.S115775. eCollection 2017.
  14. Hay PJ, Claudino AM, Touyz S, et al; Individual psychological therapy in the outpatient treatment of adults with anorexia nervosa. Cochrane Database Syst Rev. 2015 Jul 27 (7):CD003909. doi: 10.1002/14651858.CD003909.pub2.
  15. Jagielska G, Kacperska I; Outcome, comorbidity and prognosis in anorexia nervosa. Psychiatr Pol. 2017 Apr 30 51(2):205-218. doi: 10.12740/PP/64580. Epub 2017 Apr 30.
  16. Khalsa SS, Portnoff LC, McCurdy-McKinnon D, et al; What happens after treatment? A systematic review of relapse, remission, and recovery in anorexia nervosa. J Eat Disord. 2017 Jun 14 5:20. doi: 10.1186/s40337-017-0145-3. eCollection 2017.
Author:
Dr Mary Harding
Peer Reviewer:
Dr Jacqueline Payne
Document ID:
1806 (v27)
Last Checked:
24 July 2017
Next Review:
23 July 2022

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