Eating disorders

Authors: Amy Talbot / Editor: Frances Balmer / Codes: / Published: 31/03/2022


Eating disorders are serious conditions with both psychological and physical complications. They are becoming increasingly common. It is estimated that 3.4 million people in the UK are affected by an eating disorder; up to 15% of young women and 5.5% of young men.

The most common age of onset is mid-adolescence, ranging from 15 25 years and so these patients can present to both adult and paediatric emergency services.

Although eating disorders are classified as mental disorders, the physical complications can be life-threatening. Mortality rates for people with eating disorders are almost twice as high compared to the general population. In the adolescent group anorexia nervosa has a higher mortality than other serious adolescent diseases such as asthma or type 1 diabetes.


Eating disorders are complex mental illnesses associated with the disturbance of eating or eating-related behaviours. The types of eating disorder are:

  • Anorexia nervosa restriction of food or behaviour to limit weight gain, often associated with disturbed body image and fear of gaining weight.
  • Bulimia nervosa recurrent episodes of uncontrolled eating of large amounts (binge eating) followed by compensatory behaviours such as self-induced vomiting, laxative abuse or excessive exercise (purging).
  • Binge eating uncontrolled eating of large amounts in short periods without the compensatory behaviours.
  • Avoidant/restrictive food intake disorder (ARFID) avoiding certain food types. This could be a sensory-based avoidance such as taste or smell, or patients may have had a distressing experience, such as vomiting or abdominal pain, creating fear and anxiety around a food
  • Other specified feeding or eating disorder (OSFED) symptoms of an eating disorder that dont meet the diagnostic criteria for other disorders.

The cause of eating disorders is unknown, but it is thought to be a complex combination of genetic, psychological and neurobiological factors.

Risk factors include:

  • Gender 90% females
  • Family history of eating disorder or psychiatric disorder
  • Psychological anxiety, depression, low self esteem
  • Social factors poor support, isolation, household stresses
  • Neurobiological associated with abnormal neurotransmitter activity

Eating disorders have significant psychological impacts for patients, including anxiety, depression, social withdrawal and suicidal ideation.

Physical complications in anorexia nervosa occur due to the malnutrition associated with starvation.


Patients with eating disorders may appear deceptively well, and often try to hide their behaviours, so a collateral history from parents or carers may be appropriate.

The SCOFF questionnaire is an effective screening tool for identifying patients with eating disorder behaviours:

A score of 2 or more is suggestive of eating disorder behaviours.

Patients with eating disorders will not usually seek help for their eating behaviours, but for the physical complications. When taking a history, it is important to ask about:


Key points for examination include:

Weight – It is important to get an accurate weight of the patient, and this can be a sensitive issue. It should be performed in light clothing, without shoes.

BMI – Calculate and plot on BMI chart.

% median BMI – due to variations in weight and height as children and young adolescents grow and go through puberty, calculating % median BMI is advised to give a measurement in context of that patients weight and height.

Cardiovascular – as weight loss impairs cardiac function, a thorough cardiovascular exam is required, including:

Muscle wasting and strength

  • sit-up test sitting up from lying down without using hands
  • squat test rising to standing from a squat position without using hands

General exam

  • Temperature
  • Hydration
  • Abdominal exam
  • Evidence of complications e.g. lanugo hair, dental erosion
  • Evidence of deliberate self harm


Investigations to help decide if a patient requires admission include

ECG all patients should have an ECG. Check for:

  • Bradyarrhythmias
  • Long QTc
  • Non-specific T wave changes
  • Hypokalaemia

Blood tests may be normal unless there are purging behaviours, such as laxatives or diuretics:

  • FBC
  • U&Es may be affected by dehydration, or malnutrition
    • Low sodium suggestive of water loading
    • Low potassium suspicious of vomiting or laxative abuse
  • Glucose hypoglycaemia maybe associated with possible occult infection
  • Calcium
  • Magnesium
  • Phosphate
  • LFTs raised transaminases with malnutrition

Additional investigations may be required, if admission is being considered, to assess nutritional state:

  • Thyroid function tests
  • Amylase
  • Coeliac screen
  • Vitamin D
  • Iron studies, vitamin B12, folate
  • Zinc, copper selenium

Risk stratification

Not all patients require admission, some can be well managed in the community. It is important to consider the trajectory of the eating disorder, any recent stresses or escalated behaviours, support networks that are available, and what may be achieved by admission at this time.

That said, patients with eating disorders can appear deceptively well and it is important to have a low threshold to consider admission.

Those patient who should be admitted include:

  • Patients at high risk from their eating disorder. These patients may require admission to a psychiatric unit. The Mental Health Act 1983 (amended 2007) allows for compulsory admission and treatment.
  • Patients with another psychiatric disturbance such as self-harm or suicidal ideation will need a mental health review with a view to possible admission.
  • Patients with physical complications may require admission if medically unstable. The Royal College of Psychiatrists (RCPSYCH) have produced the MARSIPAN guidelines, to assist clinicians assessing patients with eating disorders.

MARSIPAN: Management of Really Sick Patients with Anorexia Nervosa

For patients under 18yrs the Junior MARSIPAN guidelines provide a detailed traffic light system to aid risk assessment. There is also a Junior MARSIPAN app which contains a quick risk assessment tool and percentage median BMI calculator.

Junior MARSIPAN: Management of Really Sick Patients under 18 with Anorexia Nervosa

Table 1: Summary of high-risk factors which indicate admission for medical input may be required.

As an inpatient

1) Early nutritional rehabilitation is key to improving the patients condition. Food is the best medicine for a patient with an eating disorder, in the same way antibiotics are the best treatment for a patient with a bacterial infection. This includes

  • Meal plans with dietician input
  • Oral supplements of phosphate, thiamine, vitamin B and multivitamins

2) Regular psychiatric review

3) Management of any medical complication arising from the eating disorder, such as electrolyte abnormality, dehydration or a concurrent illness.

4) Bed rest

5) Regular monitoring

  • Continuous ECG monitoring if abnormalities present
  • Regular blood sugars
  • Regular weights
  • Refeeding bloods

Patients should be closely monitored for refeeding syndrome. When feeding recommences suddenly after a prolonged period of starvation, the increase in electrolyte requirements as metabolism shifts can be potentially fatal. Phosphate levels can drop quickly during the first week, so daily blood tests are required for this period.

  • Patient with eating disorders can appear deceptively well, and often try to conceal their eating behaviours or underplay the severity of their condition.
  • Patients may try to falsify their weight by drinking excess water or having heavy items in pockets.
  • It is important to do a cardiovascular examination with a patient in a relaxed state. A low heart rate on examination may drop even further.
  • Daily electrolyte monitoring is needed when refeeding is started, to monitor for refeeding syndrome.
  • There is a high correlation of eating disorders with abuse or neglect. Dont be afraid to ask about home life or any other worries.
  1. National Institute for Health and Care Excellence. Resource impact report: Eating disorders: recognition and treatment. NICE guideline (NG69). May 2017.
  2. Royal college of Psychiatrists. Position statement on early intervention for eating disorders (PS03/19). May 2019
  3. National Institute for Health and Care Excellence. Clinical Knowledge Summaries. Eating Disorders. NICE CKS. Last reviewed July 2019.
  4. BEAT. Learn about eating disorders (internet).
  5. Allison E, Dawson N, et al. Fifteen minute consultation: A structured approach to the management of children and adolescents with medically unstable anorexia nervosa. Arch Dis Child Educ Pract Ed. 2017 Aug;102(4):175-181.
  6. Royal College of Psychiatrists. Junior MARSIPAN: Management of Really Sick Patients under 18 with Anorexia Nervosa. 2012.
  7. Royal College of Psychiatrists. MARSIPAN: Management of really sick patients with anorexia nervosa 2nd edition. 2014.
  8. Morgan, JF, Reid F, Lacey JH. The SCOFF questionnaire: assessment of a new screening tool for eating disorders. BMJ. 1999;319:1467 1468.

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