Eating disorders

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An eating disorder is a compulsion to change you eating habits in such a way that it adversely affects your physical or mental health. There are only really two eating disorders - anorexia nervosa and bulimia nervosa.

Anorexia Nervosa


This man does not have anorexia

Anorexia nervosa is characterised by low body weight and poor body image with an overvalued idea of how much the patient weighs, resulting in obsessively trying to shed weight.

(NB: although the condition is colloquially referred to as 'anorexia', strictly speaking this simply means 'reduced appetite'.)


90% of sufferers are women and 10% are men. It has an incidence of 8-13/100000 of the population per year and a prevalence of around 0.3%. The condition generally affects adolescent and young adult females, 40% of cases being 15-19 year old females.

Risk Factors

Genetics has a significant influence in predispostion, twin studies showing it is about 50% of the cause. There are also a variety of biological, psychological, social and cultural factors.

Clinical Features

The primary diagnostic criteria are:

  • Refusal to maintain body weight (above 85% of expected)
  • Obssessive fear of gaining weight
  • Poor insight
  • Amenorrhoea (at least three absent periods)


  • Growth Hormone - high due to low carbohydrate intake
  • FSH, LH - maybe reduced
  • Prolactin - usually reduced at night but not during the day
  • TFTs - T3, T4 and TSH (do not treat hypothyroidism as it is secondary to anorexia)
  • Cortisol - high/normal
  • ESR - low/normal (elevation suggests organic disease)


Treatment of anorexia nervosa is primarily psychological and supportive. Although there is little evidence that pharmocological therapies work, medication may be prescribed for comorbid conditions but care needs to taken as the poor physical state may be affect or be affected by medication.

Psychological Therapy

CBT is the primary psychological therapy in anorexia treatment. Other therapies include interpersonal therapy and a variety of other talking therapies.

Managing Weight Gain

Roughly 0.5kg-1kg per week should be the aim (0.5kg outpatient). This requires between 3500 and 7000 extra calories a week. Regular physical monitoring is also required.

Bulimia Nervosa


Bulimia nervosa is a disorder characterised by binge-eating and extreme dietary restraint (usually starving or self-induced vomiting).


It has a prevalence of approximately 1-2% in the Western female population and is seen primarily in caucasians.

Risk Factors

Predisposing factors include:

  • female adolescence
  • history of obesity
  • low self-esteem
  • history of depression
  • positive family history for eating disorders

Precipitating factors include general stresses and pressures to conform.

Clinical Features

Although the main features are binge-eating and subsequent vomiting, bulimia has a much wider clinical picture. The symptoms can be split into two main categories - psychological and physical.


  • concerns about body image
  • urge to overeat
  • isolated binges
  • binge eating followed by feelings of disgust and subsequent self-induced vomiting
  • depressed mood (> in anorexia nervosa)
  • social withdrawal (< in anorexia nervosa)
  • impaired concentration


These are primarily the complications of repeated vomiting:

  • potassium depletion (and its sequelae)
  • erosion of dental enamel
  • knuckle callouses (from scraping on teeth whilst inducing vomiting)
  • swollen salivary glands


  • U&E's - hypokalaemia due to vomiting, electrolyte disturbance in general.


Although it is a psychiatric disorder, understandably has physical consequences. As such, it's management is split into psychological, pharmacological and physical management.


  • Self-help programmes
  • CBT


SSRIs (generally fluoxetine) are the treatment of choice in bulimia and have been shown to reduce frequency of binges. Success will usually become apparently quickly.

Physical Management

This very important in people who abuse laxatives or vomit frequently. Fluid and electrolyte balance must be assessed. Although it should be avoided as a matter of course, if medical intervention is required, it should be given orally in the absence of contraindications.