Eating disorders

Anorexia nervosa was first described by William Gull in 1868 and is characterised by deliberate and extreme weight loss. In bulimia nervosa, episodes of overeating are followed by self-induced purging, usually in the form of vomiting. There is considerable overlap between these two eating disorders.

Anorexia nervosa

Concerns about weight, and dieting in order to lose weight are extremely common in the general population, particularly among young women. Anorexia nervosa represents an extreme form of this behaviour. Fear of being fat leads to the adoption of a starvation diet. Weight falls to at least 15% below normal, so that the body mass index (BMI) is 17.5 or less (Fig. 1). Despite this, anorexics continue to believe they are overweight, even when faced with their emaciated reflection in the mirror. This distorted body image drives them to continue to lose weight, and they may adopt other methods such as excessive exercise, self-induced vomiting or abuse of laxatives, diuretics or appetite suppressants such as amphetamine. They may become preoccupied with food, hoarding it, or becoming very interested in cookery, creating elaborate meals for their family while still refusing to eat. Amenorrhoea occurs in the early stages of weight loss and is an indication of a widespread endocrine disorder. Figure 2 shows the signs and symptoms found in anorexia nervosa.

Fig. 1 Body mass index (BMI).

Fig. 2 Signs and symptoms of anorexia nervosa.

Bulimia nervosa

In bulimia nervosa there is also a fear of fatness, but the characteristic symptom is binge eating. ‘Binges’ are the consumption of huge quantities of food at a single sitting, particularly carbohydrate-rich items such as biscuits, cakes and bread. They often take place in secret, and away from meal times. Some bulimics will eat normally at other times, although calorie-controlled diets are common. A small number also have anorexia nervosa. In bulimia nervosa, binges provoke feelings of guilt and disgust and a sense of being out of control. These feelings lead to a desire to get rid of the food, usually achieved by putting fingers down the throat to induce vomiting. Many bulimics are eventually able to spontaneously vomit. As in anorexia, laxative and diuretic abuse may be further threats to health. Despite a dread of weight gain, many maintain a normal weight and may even be overweight. Menstruation is often normal.

Epidemiology

Bulimia is more common than anorexia nervosa. Anorexia nervosa usually starts in adolescence, and bulimia a few years later. Surveys of young women have found a prevalence of 3–4% for bulimia and 1–2% for anorexia nervosa. Both are more common in women than men. Occupations that depend upon keeping a low body weight, such as ballet dancing and modelling, have a particularly high risk of anorexia.

Aetiology

The aetiology for both anorexia nervosa and bulimia nervosa is similar. There are many factors thought to be important and most cases will be due to a combination of causes.

Predisposing factors

Cultural factors. Anorexia nervosa and bulimia nervosa are disorders of the food-rich developed world. Western society has developed a stereotyped view of physical attractiveness which equates ‘thin’ with ‘beautiful’, and promotes negative attitudes about obesity. The media bombard us with idealised images of underweight models alongside advertisements for confectionery. Adolescents are particularly vulnerable to these cultural pressures to conform and to be attractive.

Genetic factors. Twin studies have shown that genetic factors do play a role, probably by creating a vulnerability to weight loss so that in the presence of environmental pressures an eating disorder may develop.

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