The brains of individuals with bulimia nervosa react differently to food rewards, researchers at UC San Diego (UCSD) have found.
“Our study suggests that adults with bulimia nervosa may have elevated reward-related brain activation in response to taste," said Alice V. Ely, PhD, principal author of the study in the Department of Psychiatry at UCSD School of Medicine, in a statement.
Bulimia nervosa (BN) is an eating disorder that leads to frequent periods of binge eating followed by efforts of purging to avoid weight gain, according to university officials. The findings show how specific brain mechanisms involved in the eating disorder could lead to new treatment therapies.
"This altered neural response may explain why these individuals tend to remain driven to eat even when not hungry,” said Ely.
Part of the drive to eat stems from two different brain mechanisms. That includes metabolic, which is actual hunger, and hedonic, which is the desire for a reward.
According to researchers, the findings -- published July 10 in the Journal of Abnormal Psychology -- made progress on understanding how the interaction of both mechanisms produces the disorder.
“We found that the areas of the brain that differed in the two study groups were the left insula, putamen and amygdala, which determine how rewarding a taste might be and how emotionally important it is," said Ely. "That information is then sent to parts of the brain that motivate eating."
There were 26 patients with BN and 22 without the disorder participating in the study, said researchers. The group was given water and a sucrose solution every 20 seconds, for about 13 minutes.
The solution was given after the patients either fasted for 16 hours or ate a standard breakfast.
“We wanted to see how their brains reacted to different tastes and hunger states,” said Ely.
The group without the disorder would enjoy food rewards more after they had fasted and were very hungry. Interestingly, the group with the disorder would respond the same way to food rewards after eating or fasting.
“Brain activation in the left amygdala was actually significantly greater in the group with a history of bulimia nervosa than in the control group when fed, indicating that taste response in these individuals may be insensitive to the effects of energy metabolism, exaggerating the value of food reward,” said Ely.
“If you’re full and your brain is telling you to keep eating, it could contribute to loss of control," added Ely.
Nearly five million women and two million men in America suffer from BN, said researchers. The current treatment options are effective for about 30 to 50 percent of patients.
“Our study results may contribute to identifying neural mechanisms that will open the door to the use of new medications or other brain-based behavioral treatments,” said Ely. “This is promising and hopeful news to those who suffer from eating disorders.”