Eating Disorders (Including anorexia nervosa and bulimia nervosa)

1. How common are eating disorders?

Eating disorders are much more common in female, with a female-to-male ratio of 10:1, but there is an increasing trend for men and boys. About 1 out of 200 school girls suffer from anorexia nervosa, but the prevalence is up to 6% among ballet dancers or models. Bulimia nervosa is about 5-10 times more common than anorexia nervosa. About 2-3% of young women suffer from bulimia nervosa.

2. What are the features of anorexia nervosa?

Most of us are concerned about our body weight, so we would pay attention to our diet and do physical exercise for managing body weight. Anorexia nervosa happens when the concern on body weight has gone to extreme, leading to a relentless pursuit of thinness and subsequently malnutrition and physical ill-health.

In anorexia nervosa, the patient reduces her body weight by dieting, vomiting, excessive physical exercise, or use of medication (e.g. appetite suppressant, laxative and diuretics). The behaviour is driven by an extreme fear about being fat or from a strong desire to be thin. So, the patient does not lack a sense of hunger; actually the patient cannot stop thinking about the food. However, the utmost fear about fatness and the intense desire on thinness prohibit her from eating. The patients might be engaged in making food for others or pushing others to eat, while she avoids eating in front of others, over-report what they have eaten.

As a result, the patient loses much body weight. Since appropriateness of body weight takes body height into account, a body mass index (BMI) is used to relate weights to height. Body mass index = weight (kilograms)/height (metres)2. A normal BMI for Chinese is 18-23 kg/m2. In anorexia nervosa, the BMI is below 17.5kg/m2. Apart from loss of body weight, muscle strength and bone strength, the hormone function was disturbed, and the most notable change is the stopping of menstruation in female or loss of impotency in men.

3. What are the clinical features of bulimia nervosa?

In bulimia nervosa, the patient is preoccupied with food and feels losing control over eating. Like a patient with anorexia nervosa, she dreads fatness. She binge eats, and feel shame and guilt after the binge-eating. To counteract the calorie gain from the binge eating, she self-induces vomiting, takes laxative or excessively exercises. As a result, she is caught in a cycle of binge-eating and purging. Therefore, unlike anorexia nervosa, a patient with bulimia nervosa usually does not have a low body weight.

4. What are the causes of eating disorders?

The biological dysfunction in brain causing the mental symptoms of eating disorders is still unknown. Genetic factors are implicated; there is a 7-12-fold increase in the risk if there is a family history of eating disorder. Abnormality in the function of serotonin, a neuro-transmission, is believed to be involved. Serotonin is important in the regulation of food consumption.

More is known about the possible environmental factors of eating disorders. The notion of “thinness as beauty” prevails in the Western culture, and the promotion of dieting and body weight reduction programme in the mass media influence young girls’ perception of body image. Nonetheless, a cultural or societal influence alone seems to be inadequate to explain why some girls develop an incredibly strong dread of fatness and strong will to relentlessly reduce their body weight.

Some common characteristics are observed in the family of anorexia nervosa patients; the families are characterized by overprotection (e.g. a mother immediately takes on any problem her daughter find difficult to manage, without giving her a chance to try on her own), conflict avoidance (e.g. the father chooses to change the subject or to put off a discussion until later, whenever there is a disagreement in the family) and enmeshment.

Enmeshment in a family means that the family members are overly involved with and reactive to one another, i.e. a lack of inter-personal boundary which is essential for all healthy relationship. It is certainly natural that parents love and protect their children and their children need their parents’ emotion support. A sense of togetherness is good in a family in which the members love one another. No matter how close they are, each family member is an individual who should have their personal affair and emotion. Excessive emotional involvement interferes with the children’s development of autonomy and a sense of identity, and it is particular a problem when the children step into adolescence. In an enmeshed family, a personal issue of a family member will echo throughout the whole family, and any act of autonomy is taken as a crisis which threatens the cohesiveness of the family. One reason for parents to be emotionally over-involved with their children is that the parents, more commonly mothers, feel threatened by the emerging sense of autonomy, and therefore act in the ways to prolong the parent-child cohesion which has been giving them a sense of security.

Facing difficulty in striving for autonomy and building her self-esteem, the adolescent takes the weight loss as an achievement which boosts their self-esteem. Gaining a tight control over their body weight gives them a sense of autonomy.

Another explanation for the adolescent onset of anorexia nervosa is that the patient fails to cope with the challenges in sexual maturity in adolescence, and therefore tries to avoid the body shape changes and menstruation by excessive dieting.

5. What are the treatments for eating disorder?

The treatment of eating disorder addresses both the mental illness itself and the physical complication. Restoration of normal body weight and establishment of a healthy eating habit is the first goal of treatment. This can be treated in an outpatient clinic if it is mild. In-patient treatment will be necessary for those with very low body weight or with physical complication. The physical complication in eating disorder can be life-threatening, for example, the electrolyte imbalance (particularly a mineral called potassium, as low blood potassium can have fatal affect on heart) and tears on esophagus and consequent severe bleeding due to self-induced vomiting. Refeeding, if introduced too rapidly can be very dangerous. Therefore, carefully controlled refeeding and close monitoring of physical condition along the process is essential.

Long term management of eating disorders, particularly anorexia nervosa, relies heavily on the therapeutic alliance and the involvement of family in the treatment programme. The ambivalence towards the illness and the complicated psychological condition (long-standing psychological difficulty accumulated from childhood, and concurrent mental symptoms such as depression and anxiety) makes engaging the patients in treatment difficult. The role of psychotropic medication is limited in eating disorder. Selective serotonin-reuptake inhibitors have some use in managing depression and binge-eating.

Numerous non-pharmacological treatments show benefit. Apart from psycho-education about nutrition and body weight, Cognitive Behavioural Therapy can address issues of control and self-esteem; Interpersonal Therapy focuses on improving social functions and interpersonal skills. Family Therapy is particularly useful for young patients who are living with their parents and have onset of illness before adulthood.