The majority of cases of obesity are caused by a combination of constitutional and social factors that encourage overeating. It is relatively infrequent for psychological causes to be involved. However, even when obesity is not due to definite psychological causes, it may itself produce a psychological reaction of depression and tension, particularly if attempts by the patient to lose weight are repeatedly ineffective.
Behavioural methods of treatment that make use of positive rewards for weight loss or for behaviour likely to lead to a reduction of weight have been attempted, but their efficacy is doubtful.
The main clinical criteria for diagnosis are:
• A body weight more than 25% below the standard weight
• An intense wish to be thin
• A morbid fear of fatness
• Amenorrhoea in women
Clinical features may include:
• Onset usually in adolescence
• A previous history of chubbiness or fatness
• A relentless pursuit of low body weight
• Usually a distorted image of own body size
• The patient generally eats little
• Particular avoidance of carbohydrates
• Vomiting, excessive exercise and purging
• Amenorrhoea-an early symptom; in 20% it precedes weight loss
• Binge eating
• Usually a marked lack of sexual interest
The physical consequences of anorexia include sensitivity to cold, constipation, hypotension and bradycardia. In most cases, amenorrhoea is secondary to the weight loss. Vomiting and abuse of purgatives may lead to hypokalaemia and alkalosis.
Case register data suggest a rate ranging from 1 to 10 per 100000 females aged between 15 and 34 years. Surveys have suggested a prevalence rate of 1-2% among schoolgirls and university students. However, many more young women have amenorrhea accompanied by less weight loss than the 25% required for the diagnosis. The condition is much less common among men. The onset in women is usually between 16 and 17 years of age and it seldom occurs after 30 years.
GENETIC. Six to ten per cent of siblings of affected girls suffer from anorexia nervosa; there is an increased concordance amongst monozygotic twins suggesting a genetic predisposition.
HORMONAL. There could be a disturbance of hypothalamic function in that:
• Amenorrhoea can precede weight loss in 20% of sufferers.
• Hormonal disturbances include low luteinizing hormone levels with impaired response to luteinizing hormone releasing hormone and to clomiphene. However, such findings could be due to the effect of prolonged fasting as they resolve after weight gain. Psychological factors
INDIVIDUAL. Patients usually have:
• A disturbance of body image
• Dietary problems in early life
Anorexia is seen as an escape from the emotional problems of adolescence and a regression into childhood.
FAMILY. The specific pattern of relationships described is characterized by:
• Lack of conflict resolution
Anorexia serves to prevent dissension in families. However, evidence in favour of such patterns is conflicting.
There is a higher prevalence in higher social classes, and a high rate in certain occupational groups (e.g. ballet students and nurses) and in societies where cultural value is placed on thinness.