Eating disorders are incredibly complex and not fully understood. While many consider eating disorders to be 100 % psychological in origin, increasing evidence suggest that have a strong physiological basis. Bulimia and anorexia are perhaps the most well studied eating disorders, but many other eating disorders exist. Increasingly, it is being accepted that certain cases of obesity may also involve a component of both psychological changes relating to an underlying physiological component, and as such may also be considered eating disorders. Anorexia nervosa is an eating disorder characterised by a significant reduction in energy intake coupled to a perception that body weight is too high despite substantial weight loss. Anorexia nervosa has been suggested to be related to the development of anhedonia, or a reduction in the ability to experience reward from eating. Therefore an indifference to food develops through an inhibition of the normal reward pathway, and this reduces total food intake.
Comparison of healthy individuals with those with anorexia nervosa shows that when exposed to sensory stimulation by highly palatable foods, healthy people respond with activation of certain areas of the brain, termed the cephalic response. However, subjects with anorexia nervosa show reduced activation of these same areas. In addition, those with anorexia respond positively to images relating to thinness and to images of underweight females, whereas normal healthy individuals show indifference to these signals. This suggests a difference in the way the brain is wired to respond to certain signals in those with anorexia nervosa. In particular, a dysfunction in the cannabinoid reward system has been suggested as a possible causative factor in the development of anorexia nervosa. Researchers have investigated the role of endogenous cannabinoids in the development of anorexia nervosa using cannabinoids and endocannabinoids in subjects suffering from anorexia nervosa and in healthy subjects.
In one study1, researchers measured circulating levels of cannabinoids and endocannabinoids in subjects suffering from anorexia nervosa and compared the levels to healthy subjects. This was performed after consumption of a number of favourite and non-favourite foods. The results of the study showed that in healthy subjects levels of one endocannabinoid compound decreased after both types of meal, but were significantly higher when a favourite meal was consumed. However in anorexia nervosa patients, the same endocannabinoid did not show observable changes following consumption of either favorite or non-favourite foods. In anorexia nervosa subjects that had restored their weight, the levels of the same endocannabinoid also differed to health controls following consumption of favourite and non-favorite foods. Slight differences in a number of other endocannabinoid-related compounds were also found between healthy and anorexia nervosa sufferers in response to favourite or non-favourite food consumption.
RdB
