• The diagnosis of an eating disorder is made on the basis of the history and suggestive clinical features. This is supported, where possible, by corroboration from a relative or friend [National Collaborating Centre for Mental Health, 2004]. See:
• Clinical features of anorexia nervosa.
• Clinical features of bulimia nervosa.
• Clinical features of atypical eating disorders.
• Be aware that eating disorders [National Collaborating Centre for Mental Health, 2004]:
• Are often difficult to detect in primary care, as people are slow to present and may only do so when persuaded by concerned family members or friends.
• Can occur in children, men, and those from ethnic minority groups.
• May present with non-specific symptoms, for example fatigue, dizziness, or lack of energy, or physical complications associated with starvation, purging, and vomiting [Wilhelm and Clarke, 1998; Pritts and Susman, 2003; Williams et al, 2008].
• Have a lower threshold for suspecting an eating disorder in [National Collaborating Centre for Mental Health, 2004]:
• Young women with low body mass index (BMI) compared with age norms.
• People consulting with weight concerns who are not overweight, or who are underweight.
• Women with menstrual disturbances or amenorrhoea.
• People with gastrointestinal symptoms.
• People with physical signs of starvation or repeated vomiting.
• Young people with Type 1 diabetes and poor treatment adherence.
• Children with poor growth.
• Women with psychological or psychiatric illness should be considered to be at risk of an eating disorder.
• To help clarify any suspicion that an eating disorder might exist consider:
• Asking the following questions [National Collaborating Centre for Mental Health, 2004]:
• 'Do you think you have an eating problem?'
• 'Do you worry excessively about your weight?'
• Using the SCOFF questionnaire. Two or more positive answers are suggestive of a case and indicate that further interview and examination are required [Morgan et al, 1999; Morgan et al, 2000].
• Do you ever make yourself sick because you feel uncomfortably full?
• Do you worry you have lost control over how much you eat?
• Have you recently lost more than one stone in a 3-month period?
• Do you believe yourself to be fat when others say you are too thin?
• Would you say that food dominates your life?
• Asking further questions which may help elicit behaviour and thought patterns suggestive of an eating disorder [King's College London, 2009]:
• Do you avoid eating with others?
• Which foods feel 'safe' and which do you avoid?
• What do you consider your ideal weight to be?
• How would you feel about gaining weight?
• Do you ever get depressed or feel guilty?
• Has your life become more ritualized?
• Do you have compulsions to do things such as bingeing?
• Do you ever exercise excessively, or abuse laxatives and/or diuretics?

Clinical features of anorexia nervosa include:

• Weight maintained at least 15% below that expected for the person. In adults this normally represents a body mass index (BMI) of less than 17.5 kg/m².
• In people younger than 18 years of age, BMI centile charts should be used. A BMI below the 2.4th centile indicates underweight. In younger people, the diagnosis may be made in those who fail to gain weight during the expected growth spurt of puberty — they can become underweight without actually losing weight.
• Self-avoidance of foods thought to be fattening to achieve weight loss. One or more of the following compensatory behaviours may also be present:
• Self-induced purging (by vomiting or excessive use of laxatives).
• Excessive exercise.
• Use of appetite suppressants.
• Use of diuretics.
• Psychological features, which may include:
• Distortion of body image, with a dread of fatness.
• Over-evaluation of self-worth in terms of weight and shape leading to pursuit of thinness.
• Weight loss viewed as a positive achievement. The person perceives others as mistaken in believing they should gain weight.
• Denial of the seriousness of the weight loss or its impact on physical health.
• Difficulty acknowledging there is a problem and ambivalence about change.
• A widespread endocrine disorder involving the hypothalamic–pituitary–gonadal axis.
• This manifests in women as amenorrhoea (to fulfil the DSM-IV American Classification System criteria this is present for three or more menstrual cycles). It is important to note that monthly bleeding in women taking oral contraceptives is not an indicator of true menstrual status.
• Men may present with loss of libido and potency.
• Before puberty, growth and physical development can be affected.
• Other symptoms, such as constipation, headache, fainting, dizziness, fatigue, and cold intolerance.
• Physical signs, such as cachexia, acrocyanosis (hands or feet are red or purple in colour), dry skin, hair loss, bradycardia, orthostatic hypotension, hypothermia, loss of muscle mass and subcutaneous fat, oedema, and lanugo hair (downy hair on the upper part of the body and face).

[WHO, 1992; DSM-IV, 1994; Pritts and Susman, 2003; National Collaborating Centre for Mental Health, 2004]

Clinical features of bulimia nervosa include:

• Recurrent episodes of binge eating (eating, in a defined period of time, much more than most people would eat under similar circumstances) which occur with feelings of loss of control over how much is being eaten.
• Compensatory behaviour (any one or a combination of vomiting, purging, fasting, or excessive exercise) in order to prevent weight gain. Misuse of laxatives, diuretics, thyroxine, amphetamines, or other medication may occur.
• The World Health Organization stresses that purging behaviour (which encompasses self-induced vomiting and laxative misuse) should be categorized as bulimia nervosa. However, the DSM-IV American Classification System criteria distinguish between bulimia nervosa with purging behaviour and the non-purging type (excessive exercise or fasting occur, but not vomiting or laxative misuse). The DSM-IV criteria state that binge eating and inappropriate compensatory behaviours both occur, on average, at least twice a week for 3 months.
• Body mass index maintained above 17.5 kg/m² in adults, although there may be a history of an earlier episode of anorexia nervosa.
• Psychological features, which typically include:
• A fear of gaining weight, with a sharply defined weight threshold set by the individual. Self-evaluation is unduly influenced by weight and body shape.
• Mood disturbance and symptoms of anxiety and tension.
• Other associated psychological symptoms including persistent preoccupation and craving for food and feelings of guilt and shame about the behaviour. Self-harm, often by scratching or cutting, is common.
• Physical symptoms such as bloating, fullness, lethargy, gastro-oesophageal reflux, abdominal pain, and sore throat (from vomiting).
• Physical signs in severe cases, such as knuckle calluses (from inducing vomiting; Russell's sign), dental enamel erosion, and salivary gland enlargement. In practice these are not seen in the majority of people presenting in primary care with bulimic disorders.

[WHO, 1992; DSM-IV, 1994; Pritts and Susman, 2003; National Collaborating Centre for Mental Health, 2004]

• Most eating disorders encountered in the community are atypical.
• An eating disorder is described as atypical if it has features that closely resemble anorexia nervosa or bulimia nervosa but does not meet the precise diagnostic criteria for either, for example:
• The person's weight may be just above the diagnostic threshold for anorexia nervosa.
• If the body mass index is less than 17.5 kg/m², the woman may still be menstruating.
• Binge eating and purging may occur infrequently.
• Over-concern with weight and shape is generally present.
• Many people with atypical eating disorders have experienced anorexia or bulimia nervosa in the past, or may subsequently go on to develop the full syndrome.
• Atypical eating disorders are relatively commonly diagnosed in childhood, partly because it is difficult to strictly apply existing diagnostic criteria for anorexia nervosa and bulimia nervosa to children.
• Atypical eating disorders are also known as 'eating disorders not otherwise specified' under the DSM-IV American Classification System.
• Binge eating is an example of an atypical eating disorder.
• A large amount of food is eaten over a short period of time, along with feelings of loss of control.
• Binge eating episodes are associated with three or more of the following:
• Eating more rapidly than normal.
• Eating until feeling uncomfortably full.
• Eating large amounts of food when not physically hungry.
• Eating alone or in secret through embarrassment at the amount that is being eaten.
• Feeling disgust or extreme guilt after overeating.
• Marked distress regarding binge eating is present and social avoidance is common. Depressive features and dissatisfaction with shape are common, though over-evaluation of the importance of weight and shape is less marked than in bulimia nervosa.
• Many people with binge eating disorder are obese. They experience recurrent episodes of bingeing, similar to that in bulimia nervosa but without the extreme compensatory behaviours seen in people with bulimia nervosa. People tend to be older and there are more men with this disorder than is the case with the other eating disorders.

[WHO, 1992; DSM-IV, 1994; National Collaborating Centre for Mental Health, 2004]

• Laboratory investigations may be useful as part of a further assessment once a specific diagnosis is suspected. Tests that may help to exclude an alternative diagnosis of amenorrhoea and weight loss include thyroid function tests, follicle stimulating hormone, luteinizing hormone, and prolactin [National Collaborating Centre for Mental Health, 2004].

There are a large number of causes of weight loss or amenorrhoea, but in practice eating disorders should be relatively easy to differentiate from other causes when the time is taken to explore the history, including corroborative information and the person's attitude to the weight loss.

• Differential diagnosis of weight loss
• Malabsorption (for example coeliac disease, inflammatory bowel disease).
• Cancer.
• Illicit drug use or alcoholism.
• Infection (for example tuberculosis).
• Autoimmune disease.
• Endocrine disorder (for example hyperthyroidism).
• Differential diagnosis of amenorrhoea (see the CKS topic on Amenorrhoea).
• Pregnancy.
• Primary ovarian failure.
• Polycystic ovary syndrome (see the CKS topic on Polycystic ovary syndrome).
• Pituitary prolactinoma.
• Hypothalamic causes.
• Psychiatric differential diagnosis
• Depression (see the CKS topic on Depression).
• Obsessive-compulsive disorder.
• Psychosis (rare).

[National Collaborating Centre for Mental Health, 2004]