7.1 Introduction

Eating disorders are conditions in which abnormalities of eating behaviour, driven largely by psychological factors, are severe and persistent enough to impair nutrition, physical health, and social functioning, as well as cause psychological distress for the sufferer and their carers.

Broadly, the disordered eating may be a restriction of the amount, variety, and frequency of food and fluid consumed, or excessive overeating, or alternating episodes of restriction and overeating. In some individuals, there may additionally be efforts to prevent or compensate for the effects of eating, most usually by self-induced vomiting, excessive use of laxatives, or over-exercising. All of these symptoms give rise to significant physical and nutritional problems, which need to be addressed as part of the management of the condition.

7.2 Classification and features

Both the World Health Organization (WHO) and the American Psychiatric Association (APA) have published diagnostic criteria for eating disorders, which are broadly similar (see Tables 7.1, 7.2 and 7.3). The WHO and APA diagnostic criteria both recognise two major eating disorders: anorexia nervosa and bulimia nervosa. In the APA criteria – the Diagnostic and Statistical Manual of Mental Disorders (DSM IV-TR) – anorexia nervosa is divided into two subtypes: restricting and binge–purge. There are additional diagnoses, classified in the DSM as Eating Disorders Not Otherwise Specified (EDNOS), which include partial syndromes and binge-eating disorder.

These criteria demonstrate the difficulties inherent in separating disordered eating from the range and variety of normal eating, and in separating eating disorders from one another. These separations are necessary for precision in communication and research. In practice, it may sometimes be more realistic to regard eating disorders as a spectrum along which individuals can move during the course of their illness. Nevertheless, there are clear differences between the major syndromes, not only in the presenting features but also in the predisposing and maintaining factors, and so it is useful to distinguish between them in examining aetiology, epidemiology and management.

Anorexia nervosa

The central feature of anorexia nervosa is restriction of food intake, which is severe and persistent enough to maintain body weight well below normal. Diagnostic criteria set 15% below normal weight, or body mass index (BMI) 17.5 kg/m², as the cut-off in adults (Table 7.1). Ideally, the normal weight would be the pre-morbid healthy weight for the individual, if this were known, but practitioners often find they must rely on standard body-weight tables for whole populations, or normal BMI ranges. In such cases, care is needed to use standards for the appropriate ethnic group. In children and young people below the age of eighteen, some skill is needed to interpret the comparison of an individual with anorexia with norms shown on standard growth charts, as height as well as weight may be affected by under-nutrition.

Table 7.1 Diagnostic criteria for anorexia nervosa. Reprinted with permission from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, (Copyright 2000). American Psychiatric Association.

Usually, the foods most stringently avoided are those perceived to be most likely to cause weight gain –
typically high-fat and high-sugar foods – and there may be an escalating reduction in the variety of foods eaten as the illness progresses. This may typically begin with exclusion of the high-fat and -sugar foods, then other foods containing fat such as red meat, cheese, and eggs, and at its most severe it can leave little more than fruit and vegetables. Vegetarianism is common.

The restriction is almost always driven by over-valuation of shape and weight as a basis for self-worth, driving a persistent and overwhelming wish to lose weight, in spite of having a body weight below – sometimes severely below – normal. Restriction of food intake may also be driven by a wish for control, often in the context of a life with many stressful and uncontrollable events; by anxiety reduction and seeking of illusory safety; and by perfectionistic pursuit of compliance with rigid rules. There is commonly a distortion of body image, characterised by a conviction of being fat in spite of low body weight; and resistance to accepting that the behaviour is harmful. Occasionally, however, the wish to lose weight is not the primary driver, which may instead be overzealous striving for religious or spiritual purity, an attempt to manage physical symptoms perceived to be food-related – for example, the conviction of having multiple food allergies or sensitivities – or extreme and distorted pursuit of healthy eating.

Female athletes may exhibit the so-called ‘athlete’s triad’ of disordered eating, amenorrhoea, and low bone mineral density, especially in sports where low weight is necessary, such as distance running and gymnastics. Ballet dancers may be similarly affected.

Table 7.2 Diagnostic criteria for bulimia nervosa. Reprinted with permission from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, (Copyright 2000). American Psychiatric Association.

Other diagnostic features result from the starvation itself. The endocrine disorder is mediated by the hypothalamus and the pituitary, affecting the gonads, thyroid, and adrenal glands. The reduction in oestrogen in females results in the cessation of menstruation, which is a diagnostic feature. The reduction in thyroid function contributes to a range of physical abnormalities, including bradycardia, hypotension, and hypothermia. There is failure of growth and pubertal development in children and adolescents.

Some individuals with anorexia nervosa may make additional efforts to reduce body weight by vomiting, especially if an eating is, or is perceived to be, a binge, unplanned, uncontrolled, inappropriate food, or otherwise unacceptable. Laxatives, diuretics, and excessive exercise may also be employed.

In some individuals, there may be persistent cycles of restriction, binge eating, and purging. The DSM distinguishes two subtypes: restricting and binge–purge, though purging behaviour may occur without any bingeing.

Bulimia nervosa

The defining feature of bulimia nervosa is a cycle of restriction of eating, which may be very severe, followed by food craving and uncontrolled excessive eating. This raises anxiety about the possible weight increase the binge might cause, provoking attempts to compensate, most commonly by self-induced vomiting, excessive use of laxatives, or excessive exercise, and further restriction of eating (Table 7.2). This binge–starve cycle is driven by over-valuation of thinness and by attempts to lose weight as a means to improve low self-esteem. BMI must be above 17.5 kg/m², or the diagnosis would be anorexia nervosa. It is most usually in the normal range, but may be above or below normal, and is often erratic.

Table 7.3 Diagnostic criteria for partial syndromes and binge-eating disorder. Reprinted with permission from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, (Copyright 2000). American Psychiatric Association.

EDNOS and binge-eating disorder

As shown in Table 7.3, the DSM IV-TR diagnostic criteria include a number of partial syndromes.

Diagnostic criteria for binge-eating disorder were first proposed and tested by Spitzer et al. (1992). Binge-eating disorder is characterised by repeated episodes of binge eating, without significant compensatory behaviours, though there may be a history of repeated attempts at dieting. There is no objective measure of a binge, though some individuals report eating several thousand calories in a short period of time. Episodes of eating large amounts are a normal response to a period of restricted eating, and are also normal in most cultures as part of social celebration. In binge-eating disorder, the binges do not have these normalising contexts, and are associated with severe distress. Levels of concern about weight and shape are similar to those in the other eating disorders, and higher than in obese people without binge-eating disorder. Binge-eating disorder is usually associated with weight cycling and obesity, which may be severe.

7.3 History

Disordered eating has been described for centuries, though the details of presentation and contemporary interpretations have varied.

From antiquity onwards, there are descriptions of extreme, apparently deliberate, restriction of food intake resulting in severe weight loss. In mediaeval and Renaissance European cultures, this seems to have presented most commonly as overzealous religious fasting. In early modern times, belief in magic and witchcraft was widespread, and regarded as part of the natural order of the world. The appearance of living without eating was viewed as a ‘natural wonder’ in a culture where many such apparent miracles were described, including for example young women giving birth to rabbits and boys vomiting pins. A view of self-starvation as a natural illness emerged at this time, exemplified in Morton’s famous description of a condition recognised as ‘nervous atrophy’. In 1694 he described a young woman unable to eat and losing flesh, which he ascribed to ‘violent passions of the Mind’. This view moved in to mainstream medicine in the late nineteenth century, with descriptions in the medical literature by Lasègue in France and Gull in England. In 1888 Gull coined the term ‘anorexia nervosa’, and by then he clearly considered it a primarily psychological or ‘nervous’ condition. In the twentieth century, pursuit of slimness emerged in Europe and North America as a widespread cultural phenomenon, and as the predominant driver of restriction of eating in anorexia nervosa, to the extent that it has been included as a diagnostic criterion since the 1960s.

Likewise, binge eating associated with loss of control has been described from antiquity. This is arguably a natural and appropriate response to food deprivation, and also social celebration. Self-induced (or doctor-induced) vomiting has also been described for thousands of years, often in attempts to prevent or treat illness.

In 1979, Gerald Russell described a new eating disorder, linking binge eating and purging in the context of a drive for thinness, and coined the term ‘bulimia nervosa’ for it. He described this disorder as characterised by a cycle of restriction of eating, followed by an episode of uncontrolled and extreme overeating, then attempts to prevent the weight-gaining effect of the binge by self-induced vomiting, use of laxatives, over-exercise, or other means. He related it to anorexia nervosa, as he recognised that the disorders share the underlying fear of fatness and over-valuation of thinness. Although Russell viewed it as a variant of anorexia nervosa, it rapidly became clear that bulimia nervosa can occur at any weight, and most usually at or close to normal weight. In later diagnostic criteria, bulimic features in people with a BMI below 17.5 kg/m² are allocated the diagnosis of anorexia nervosa, binge–purge subtype.

7.4 Aetiology

Biological, psychological, and environmental factors interact to increase vulnerability to eating disorders.

There is clear evidence of heritability in all eating disorders, most strongly in anorexia nervosa. It may be that some of the genetic vulnerability is shared with other psychiatric disorders, such as depression, anxiety, obsessive–compulsive disorder, and substance misuse, and many individuals with eating disorders also have these conditions.

The genetic predisposition may be mediated by personality traits. Personality traits are discernible from childhood, and persist after recovery from the illness. Perfectionism, rigid and rule-bound thinking, and compulsivity are associated with eating restraint. Novelty-seeking and impulsivity are associated with binge eating. These traits may arise from genetic influences on brain neurotransmitters, with serotonin of particular interest because of its role both in eating behaviour and in mood. These distinct thinking styles influence the individual’s response to environmental factors such as parenting style, stressful events such as childhood sexual abuse, bereavement and loss, or bullying, and also cultural influences such as the over-valuation of thinness.

Puberty seems to be a particularly vulnerable time for these factors to come together to bring about the development of an eating disorder, as body changes, in particular increase in weight and, for girls, adiposity, interact with increasing social awareness and sensitivity.

Dieting to attempt to reduce body weight is very widespread behaviour among girls in Western cultures, and is a common precursor of eating disorders, often, though not always, in the absence of clinical overweight or obesity. It has been suggested that cultural over-valuation of thinness, especially as promoted by advertising and other media, has a role in promoting eating disorders. It is not clear exactly what this contribution is, but one way it may operate is by increasing the number of young people, especially girls, who diet.

This view of eating disorders arising typically during or shortly after puberty, from a multiplicity of factors, is supported by some elements in the epidemiology, in particular the age of incidence, and the very much higher prevalence in females than in males.

7.5 Incidence and prevalence

Authors considering the epidemiology of eating disorders often urge caution, and suggest that published figures may be underestimates, for a number of reasons, including secrecy about symptoms and reluctance to seek treatment. For example, in one community sample, half of the cases of anorexia nervosa had not been detected by healthcare services. A study of young people in America found that 34% of boys and 43% of girls has some signs of disordered eating. Individuals may move over time from one diagnostic classification to another.

Anorexia nervosa

The highest incidence of anorexia nervosa is at age 15–19. In Europe and the USA, prevalence of anorexia in that age group is around 0.3%, and lifetime prevalence is about 0.6–0.9%. Overall incidence in these populations is at least 8 per 100 000 per year for anorexia nervosa. The female-to-male ratio is generally found to be about 10 : 1, though this difference is less marked in children and adolescents than in adults. Outside Western societies, prevalence is lower, and the exact presentation differs, but there is some evidence that it is increasing with the spread of Western cultural norms.

Bulimia nervosa

Incidence of bulimia nervosa is much higher than that of anorexia nervosa, at about 1–1.5% among young women in Europe and North America. For young men, as in anorexia nervosa, the prevalence is about 10% of that for females. Over whole populations, incidence rates of about 12 per 100 000 per year have been found.

EDNOS and binge-eating disorder

It is likely that partial syndromes are more commonly seen in clinical practice than presentations of disorders meeting the full diagnostic criteria for anorexia or bulimia nervosa. The prevalence of binge-eating disorder is probably about 3% of whole populations in Western societies, with a more even distribution between males and females. It may be as much as 25% among people seeking treatment for severe obesity.

7.6 Medical complications of eating disorders

Starvation and low weight

The malnutrition arising from anorexia nervosa can be severe and life-threatening.

Anorexia has long been recognised as having the highest mortality of any mental disorder. A meta-analysis in 1995 included 42 published studies, and found a crude mortality rate from anorexia nervosa of 5.9%. In 2007, a review of 10 reports found a similar rate of 5.25%. Significant causes of death include suicide and cardiac complications. There are concerns about the risk of death resulting from inappropriate refeeding practice.

There is no organ or tissue that is not affected by the deficient nutrition. Some of these changes cause significant functional impairment. Many reverse quickly with refeeding, though some may have lifelong impact.

Musculoskeletal system

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