Altered Insula Response to Sweet Taste Processing in Recovered Anorexia and Bulimia Nervosa: a Matter of Disgust Sensitivity?

To the Editor: In the June issue, the Journal published an interesting study on recovered anorexia nervosa and bulimia nervosa (1). The authors of this research used sweet tastes, with (sucrose) and without (sucralose) caloric content, to interrogate gustatory neurocircuitry involving the anterior insula and related regions that modulate sensory-interoceptive-reward signals in response to palatable foods. In particular, the right anterior insula response to sucrose was diminished in anorexia nervosa and exaggerated in bulimia nervosa relative to comparison subjects.

This abnormal insula response associated with the exposure to sweet compounds led the authors to conclude that there may be a failure to accurately recognize hunger signals. This conclusion is consistent with the suggestion that an altered interoceptive awareness may be a precipitating and reinforcing factor in both populations, although this altered awareness leads to antithetical feeding behaviors.

The neural pattern observed by the authors suggests another, not mutually exclusive, interpretation of the result, which refers to the hypothesis of an altered disgust sensitivity.

As suggested by Chapman and Anderson (2), disgust may be particularly strongly associated with visceral changes, consistent with its apparent origins in defending against the ingestion of contaminated foods. Given the key role of the anterior insula in interoception (3) and disgust processing (4), one could argue that the reported abnormal activity of this neural region in response to sweet tastes may reflect an altered disgust processing at the visceral level.

This suggestion is supported by research examining disgust sensitivity in these clinical populations before recovery. For example, Aharoni and Hertz (5) reported that patients with anorexia nervosa scored consistently higher on all domains of disgust sensitivity, with a particular regard to the food domain. Moreover, Troop et al. (6) reported higher levels of disgust sensitivity to food in bulimia nervosa. On the other hand, Houben and Havermans (7) reported lower disgust sensitivity in overweight individuals.

Given the evidence of this relationship between disgust sensitivity and feeding behavior, an assessment of disgust sensitivity could provide important clues for interpreting the pattern of neural activity reported by Oberndorfer et al. (1) in the anterior insula of patients with recovered anorexia nervosa and bulimia nervosa.