Anorexia may rewire how the brain responds to taste
A unique difference in how the brain responds to taste may help explain how eating disorders develop in individuals and open the door to potential future treatments according to a new study published in the journal JAMA Psychiatry.
A group of researchers from the University of Colorado Anschutz Medical Campus says they have found evidence that the brains of people with anorexia may respond to taste with high anxiety and a drive for thinness. This suggests their brains may be wired differently and could drive the development of anorexia as they age.
The researchers observed patients with anorexia, as well as a control group, as they tasted sugar during brain imaging.
The scans showed that the brains of those with anorexia responded significantly more than those in a control group, but this response was directly related to high anxiety and less weight gain in those with anorexia.
Interestingly, those with more severe cases of anorexia showed the strongest response. As patients restricted their diet, the researchers observed that brain reward circuits associated with dopamine became more active, triggering food avoidance and anxiety.
“When you lose weight your brain reward response goes up,” said Dr. Guido Frank, MD, associate professor of psychiatry and neuroscience at the University of Colorado School of Medicine. “But instead of driving eating, we believe it elevates anxiety in anorexia nervosa, which makes them want to restrict more. This becomes then a vicious cycle.”
In the study, 56 girls between the ages of 11- and 21-years-old with anorexia underwent brain scans, as well as 52 control participants within the same age group. The researchers instructed the participants to associate colored shapes with either receiving or not receiving a sugary solution. Then, during imaging, some participants were led to expect sugar but did not get anything. In other cases, participants were given the sugary solution when they were not expecting it.
Based on the scans, the patients with anorexia responded much more strongly to the unexpected reception or withholding of the sugary solution. However, the greater the brain response was, the greater the harm avoidance appeared to be in those with anorexia.
Harm avoidance is described as an anxiety measure for excessive worrying and fearfulness. In patients with anorexia, it is also tied to the drive for thinness and body dissatisfaction.
The team of researchers also observed that those with the highest brain responses also gained the least weight during treatment.
As the brain reward response linked to the hypothalamus, an area of the brain responsible for stimulating eating, the team suggests this phenomenon could potentially override or drive off brain signals to eat.
“An enhanced dopamine reward system response is an adaptation to starvation,” the study said. “Individuals vulnerable to developing anorexia nervosa could be particularly sensitive to food restriction and adaptations of reward response during the [mid-adolescence] development period.”
Frank believes that as anorexia progresses, it may alter brain circuits and influence the taste-ward processing mechanisms in the brain. Thus, it makes those with anorexia even more worried about shape and weight than before. Worse, it can make strong feelings of hunger potentially overwhelming or significantly anxiety-inducing.
The findings raise a number of questions about how this rewiring of the brain occurs and whether it precedes the development of eating disorders or if it may be driven by disordered eating behaviors themselves. Still, Frank and his team believe the discovery may lead to potential new treatments for eating disorders in the future.
“I hope we can use these findings to manipulate these biomarkers and design better treatments for this often-deadly disease,” said Frank.