INTRODUCTION AND OVERVIEW

Eating disorders are characterised by a preoccupation with thoughts about body weight, food, eating or exercise and a need for the person to control their weight or eating or exercise in order to stop intense negative feelings. These thoughts interfere with all aspects of the person’s daily life. This description could also include people who are very obese (BMI > 35 kg/m²) as they cannot tolerate the feeling of energy restriction that would be consistent with gentle weight loss, and it includes the third of obese people who binge eat.

The content of this chapter is limited to anorexia- and bulimia-like disorders. These eating disorders are characterised by the use of inappropriate behaviours to control body weight and feelings, as evidenced by low body weight, high body weight, extreme weight-control behaviours such as vomiting and starvation, excessive exercise and binge eating.

Eating disorders can also be thought of as ‘weight disorders’ as body weight is the major preoccupation, or ‘energy control disorders’ as they are associated with inappropriate energy control behaviours that may be associated with high, normal or low body weight. There may be only one eating disorder rather than the three or four cited by the American Psychiatric Association, as the differences are often based on artificial divisions, such as body weight or the frequency of the behaviours employed. It is often easiest to communicate about patients by describing their behaviours and their body weight. For example:

BACKGROUND

Anorexia nervosa was first described by Sir William Withey Gull in 1873, although he mistakenly assumed that the emaciated woman he discussed had no appetite. Binge eating among anorexia nervosa patients was described in 1979 and the first diagnostic criteria for bulimia nervosa was proposed in 1979. The prevalence of eating disorders is not increasing but the awareness of these problems by lay people and healthcare professionals has risen exponentially in the past 40 years. The presentation of patients can be slightly different in different cultures and appears to be changing. The emphasis on body image, with adolescent women wanting to be like skinny models and film stars, is declining. Currently the governments and public health professionals in most developed countries are attempting to educate people to try to combat the increasing incidence of obesity in all age groups of people. As a result, more adolescents presenting with eating disorders are aiming to ‘eat healthily and exercise more’, in contrast to ‘lose weight for a perfect body image’.

PREVALENCE

Current information suggests that the figures in Box 47.1 give a reasonable estimate of the prevalence of the eating disorders in women aged 13–30 years. Not all these people have sought treatment for their eating disorder and the majority are not assessed and treated by eating disorder specialists.

The eating disorders occur mostly in post-pubertal women. Approximately 1 in 15 eating-disordered people are male, although an increasing number of young males are being diagnosed with the condition in recent years. Onset is usually during adolescence or early adulthood; the peak incidence of anorexia nervosa is between 14 and 18 years, and the peak incidence for bulimia nervosa is from 18 to 25 years. Later appearance suggests that the onset is secondary to another psychiatric or medical illness.

The estimated prevalence of anorexia-nervosa-like problems is probably 3–4% and bulimia-nervosa-like 6–8%. These women are included in the EDNOS prevalence in Box 47.1. The prevalence of binge-eating disorder is thought to be 1–4%, with one in three being male, but this may not include older men and women, and may include adolescent sufferers of any or all of the other eating disorders.

AETIOLOGY

There is no consensus on why eating disorders occur. There are many explanations and these include genetic, physiological, social and psychological perspectives (Fig 47.1) and involve theories relating to childhood and adolescent development. Weight loss precedes the onset of the eating disorder. The initial weight loss may be intentional and in response to post-pubertal weight gain in women, or it may occur for other reasons such as illness or change in exercise routine.

FIGURE 47.1 Psychological factors associated with being in a negative energy balance

After a woman loses weight, particularly if there is a genetic sensitivity or the woman feels ‘good’ when she experiences the energy-deprived state, she can become preoccupied with thoughts of body weight, eating, food and exercise. She may feel unable to accept the feelings experienced while gaining body weight back to a ‘normal’ healthy range and continue to lose weight, or she may experience an overwhelming urge to eat—no matter how hard she tries to resist eating, she cannot, and binge eating occurs, only to be replaced by further attempts to lose weight. Being in a negative energy state (too little in or too much expended) helps to control negative moods and feelings.

PERPETUATING FACTORS

Factors associated with the beginnings of the eating disorder may not be those that cause it to continue for more than a brief period and possibly to become chronic (Fig 47.2). Simple examples are receiving attention from people, achieving what others cannot, being able to eat anything and not put on weight, or being a scapegoat for family problems.

FIGURE 47.2 The psychological circle of binge eating

Some behaviours appear to be self-perpetuating. Being at low weight, self-induced vomiting and excessive exercise are behaviours that become entrenched and may require considerable treatment and even hospitalisation to change. There may be a physiological basis. This is seen for starvation when a certain breed of rat is put into a running cage—as long as it has been well fed, the rat will run and eventually stop when it is tired and the novelty of the activity has decreased; if the rat is starved before being put in the running cage it will keep running until it collapses and dies. It is understood that the changes in brain chemistry associated with starvation result in the animal continuing activity in order to find food at the expense of further energy consumption. Excessive exercise may also be understood in a similar way. Self-induced vomiting is perhaps the most addictive of all and is associated with a poor outcome of treatment; it is thought that the ease of inducing vomiting has a genetic component. In all these cases it is likely that we will understand these behaviours much better when we know more about the neuropeptide neurotransmitter substances of the brain, and the appetite and feeding hormones involved in the energy balance of the body, when these behaviours are present.

All the behaviours are associated with temporary decreases in anxiety and dysphoric moods.

EATING DISORDERS IN MALES AND AMONG CHILDREN

Anorexia nervosa occurs in males and begins in the same way, and its clinical characteristics and its course are identical to that in females. Why males should pursue thinness so relentlessly is obscure, as adolescent men seek to be muscular rather than thin. Unlike women, men do not experience a rapid unwanted increase in body weight in early adolescence (they lose body fat and gain more muscle) or the accompanying loss of self-esteem. This may explain why males are older at onset of their eating disorder. Compared with female eating disorder, men who are at low weight are more likely to induce vomiting and binge-eat, and men who are at any weight are more likely to exercise excessively than women with eating disorders. Males suffering from eating disorders are likely to have additional problems including obsessive-compulsive disorder, alcohol and substance abuse and personality disorder.

A few male and female children develop eating disorders well before puberty, and again this appears to follow weight loss.

ASSESSMENT

Assessment consists of a thorough physical examination and clinical history. The typical clinical history includes:

It is helpful to see the family or partner.

The risk factors, trigger factor and perpetuating factors involved in the development and maintenance of the eating disorders (Fig 47.3) give a guide to the history. Family medical and psychiatric histories are necessary.

FIGURE 47.3 Risk factors, trigger factors and perpetuating factors involved in the development and maintenance of the eating disorders

PSYCHOLOGICAL AND PHYSICAL SYMPTOMS

The psychological changes that may accompany low weight are seen in people during starvation (Box 47.2