Mind over matter: The biology of how anorexics and bulimics override normal urges to eat

Scientists have identified neurological differences in the brains of anorexia and bulimia sufferers, which allow them to override the urge to eat. They have found that brain patterns of appetite stimulation that are normally seen in people are reversed in these patients.

Eating disorders remain widely misunderstood by scientists and by the general public. People tend to blame environmental factors for causing anorexia or bulimia, such as social pressure to remain thin.

However, an increasing number of studies have been published in recent years showing that eating disorders, like any other mental health disorders, begin in the brain. Researchers are starting to identify specific brain patterns and neural circuits that underlie these diseases.

In this new study published in Translational Psychiatry, scientists aimed to identify structural and functional brain circuits that could provide a biological insight into both anorexia and bulimia. They wanted to understand how the brain governs appetite and food intake as well as the neurological reasons behind why some people eat when they are hungry and others refrain from doing so.

White matter connectivity

The team, led by Guido Frank, an associate professor of psychiatry and neuroscience at the University of Colorado School of Medicine, recruited 77 young adult women. Twenty-six of them had anorexia, 25 had bulimia nervosa and the rest were healthy controls.

They were given a sweet sucrose solution to drink and used brain scans to assess white matter connectivity strength across the brain circuits that regulate taste-reward and food intake. They found out that people with eating disorders had widespread white matter alterations in these brain pathways – these alterations were similar for bulimia and anorexia.

They also noted an important difference in the role of the hypothalamus, the brain area that normally drives the motivation to eat. As expected, different brain regions that drove eating and taste-reward in healthy controls took their cues from the hypothalamus, but in bulimia and anorexia patients, this was not the case.

The brain patterns that were observed in fact suggested an override of the hypothalamus associated with a rejection of food intake and taste-reward signals – essentially, their brains told these people to stop consuming the sweet solution and refrained their urge to eat.

On the long term, these patterns could definitively alter the brain circuits governing appetite and food intake. It is now important to conduct studies to understand when these pattern arise and how they influence the development of the disorders.

"We now understand better on the biological level how those with an eating disorder may be able to override the drive to eat. Next we need to begin looking at children to see when all of this starts to come into play," Frank concluded.