Study: Eating Disorders May Affect Reward Response Within the Brain

Eating disorders can affect the reward response within the brain which may reinforce the eating disorder itself, based on the results of a recent study funded by the National Institutes of Health.

“The eating disorder behavior sensitizes or desensitizes the dopamine system. How the system responds, with desire or dread response, depends on your cognitive bias,” said the lead investigator of the study Guido Frank, M.D., professor of psychiatry at the University of California, San Diego.

Eating disorders like anorexia nervosa, bulimia nervosa, or binge-eating, involve behaviors such as purging and restricting food intake, which can lead to severe mental and physical health complications, including death.

Frank and researchers of the study wanted to see how behaviors across the eating disorder spectrum affect reward response in the brain, and how changes in reward response alter food intake control circuitry, and if these changes reinforce eating disorder behaviors. 

The study enrolled 197 women with different body mass indices associated with different eating disorder behaviors, such as anorexia nervosa, bulimia nervosa, binge-eating disorder, and other specified feeding and eating disorders, and 120 women without eating disorders.

The researchers used cross-sectional functional brain imaging to study brain responses during a taste reward task. During this task, participants received, or were denied an unexpected, salient sweet stimulus, which was the taste of a sugar solution.

“Most of the time they received the taste they thought that they would be getting, but sometimes they did not. That response elicits brain activation that has to do with the dopamine system,” said Frank.

The researchers analyzed the brain reward response known as “prediction error,” a dopamine-related signaling process that measures the degree of deviation from the expectation, or how surprised a person was receiving the unexpected stimulus. 

A higher prediction error indicates that the person was more surprised, while a lower prediction error indicates they were less surprised. 

“Prediction error response was dependent on low and high body weight between anorexia nervosa versus bulimia and binge eating disorder participants,” said Frank. 

The researchers also investigated whether this brain response was associated with ventral-striatal-hypothalamic circuitry, which is a fear mediated response in the brain that helps interrupt eating when need be.

“The ventral striatal hypothalamic circuitry is important because it interrupts eating if you have to. That happens when you are fearful and have to stop eating. More sensitive dopamine circuits seem to facilitate this circuitry. So, the more sensitive the dopamine circuitry is, the easier it might be to override hanger signals,” said Frank. 

For the group of women without eating disorders, Frank said the direction of the activation of the ventral striatal hypothalamic circuitry was from the hypothalamus to stratum, but this was observed to activate in the opposite direction for the group which had eating disorders. 

Researchers found that in the group of women who did not have eating disorders there was no significant correlation between BMI, eating disorder behavior, and brain reward response.

However, for the group of women with eating disorders, higher BMI and binge-eating behaviors were associated with lower prediction error response. 

Frank said this response may strengthen their food intake-control circuitry, leading these women to be able to override hunger cues. In contrast, the opposite seems to be the case for women with binge-eating episodes and higher BMIs. 

“Eating has become a fear situation, which then helps you override the hunger cue,” explained Frank.

These results suggest that women with eating disorders, eating disorder behaviors, and excessive weight loss or weight gain modulated the brain’s dopamine-related reward circuit response, altering brain circuitry associated with food intake control, and potentially reinforcing eating disorder behaviors. 

“I am not sure that [I] would call it re-wiring, rather a sensitization or desensitization which affects how you respond to things,” said Frank.

Although Frank said it can be difficult to connect the biology and behavior of eating disorders, this study provides a model for how behavioral traits promote eating problems and changes in BMI.

“Eating disorder behaviors, anxiety, mood, and brain neurobiology can interact and reinforce the vicious cycle of eating disorders, making recovery very difficult,” said Frank.

However, while the cycle of an eating disorder might be difficult to break, the study offers new insights for understanding what happens in the brain of those with eating disorders, and possible future treatments. 

“I am looking into all kinds of interventions including psychotherapy, medication and neuromodulation,” said Frank.