People with eating disorders are able to avoid food because they have trained their brains to override its own appetite signals, new research suggests.

A study published in Translational Psychiatry shows that in people with anorexia and bulimia, the “normal patterns of appetite stimulation in the brain are effectively reversed,” according to a statement from the University of Colorado Anschutz Medical Campus. Scientists from that university studied how both healthy women and women with anorexia or bulimia reacted to tasting a sugary solution and found that while in an average brain the hypothalamus motivates people to eat, the brains of women with eating disorders send signals from other regions that override the hypothalamus. The latter group of women had “widespread alterations in the structure of brain pathways” that are related to taste-reward and regulating appetite, specifically in the white matter, which is involved in communication between different regions of the brain.

 

In both anorexia and bulimia, people have a distorted body image and fear gaining weight. The eating disorders show numerous similarities, such as excessive exercise, but stand apart in one key way: People with anorexia severely restrict their food intake, or even starve themselves, and have a low body weight; those with bulimia have a tendency to eat large amounts of food in secret, known as binging, and then purge that volume, often through vomiting.

With this new research, it seems the transformation of people with eating disorders is both inside and out — the study showed that instead of different brain regions taking cues on eating from the hypothalamus, the signals were going in the opposite direction, and along weakened pathways. “As a result, their brain may be able to override the hypothalamus and fend off the signals to eat,” the university said. The disorders, which make their victims fear eating certain foods, conditioned the brain to make it respond differently to taste-reward and appetite. Dr. Guido Frank, the lead author of the study and an eating disorder expert, compared it to the idea of “mind over matter.”

“The appetite region of the brain should drive you off your chair to get something to eat,” he said in the university statement. “But in patients with anorexia or bulimia nervosa that is not the case.”

The findings reveal a neurological reason why some people eat when they are hungry, but those with eating disorders may not.