Anorexia nervosa is a serious and potentially lethal illness, which may result in death in ten percent of cases. It is characterized by the relentless pursuit of thinness, emaciation and the obsessive fear of gaining weight.
The study conducted by researchers at University of Pittsburgh and University of California, San Diego also reveals that there may be differences in the processing of information related to self-awareness in recovering anorexics compared to those without the illness.
The findings may lead to a better understanding of the cause of this serious and sometimes fatal mental disorder.
For the study, the brain activity of 32 women was measured using functional magnetic resonance imaging (fMRI.) The research team looked at images of the brains of 16 women who had recovered from anorexia nervosa - some of whom had been treated at the Center for Overcoming Problem Eating at Western Psychiatric Institute and Clinic of the University of Pittsburgh Medical Center -and 16 control subjects.
They measured their brains' reactions to pleasant taste (sucrose) and neutral taste (distilled water.) The results of the fMRI study are the first evidence that individuals with anorexia process taste in a different way than those without the eating disorder.
In response to both the sucrose and water, imaging results showed that women who had recovered from anorexia had significantly reduced response in the insula and related brain regions when compared to the control group. These areas of the brain recognize taste and judge how rewarding that taste is to the person.
In addition, while the controls showed a strong relationship between how they judged the pleasantness of the taste and the activity of the insula, this relationship was not seen in those who had recovered from anorexia.
According to Angela Wagner, M.D., University of Pittsburgh School of Medicine, who lead the study, it is possible that individuals with anorexia have difficulty recognizing taste, or responding to the pleasure associated with food.
Since this region of the brain also contributes to emotional regulation, it may be that food is aversive, rather than rewarding. This could shed light on why individuals with anorexia avoid normally pleasurable" foods, fail to appropriately respond to hunger and are able to lose so much weight.
"We know that the insula and the connected regions are thought to play an important role in interoceptive information, which determines how the individual senses the physiological condition of the entire body," said Kaye.
"Interoception has long been thought to be critical for self-awareness because it provides the link between thinking and mood, and the current body state," she added.
This lack of interoceptive awareness may contribute to other symptoms of anorexia nervosa such as distorted body image, lack of recognition of the symptoms of malnutrition and diminished motivation to change, according to Kaye.