Aurora, Colo. - Scientists at the University
of Colorado Anschutz Medical Campus have discovered the
neurological reasons why those with anorexia and bulimia nervosa are able to
override the urge to eat.
In a study published last week in the journal Translational
Psychiatry, the researchers showed that normal patterns of appetite
stimulation in the brain are effectively reversed in those with eating
Rather than the hypothalamus, a brain region that
regulates appetite, driving motivation to eat, signals from other parts of the
brain can override the hypothalamus in eating disorders.
“In the clinical world we call this `mind over
matter,’’’ said Guido Frank, MD, lead author of the study and associate
professor of psychiatry and neuroscience at the University of Colorado School
of Medicine. “Now we have physiological evidence to back up that idea.”
Dr. Frank, an expert on eating disorders, set out to
discover the hierarchies of the brain that govern appetite and food intake. He
wanted to understand the neurological reasons behind why some people eat when
they were hungry and others don’t.
Using brain scans, the researchers examined how 26
healthy women and 26 women with anorexia or bulimia nervosa reacted to tasting
a sugary solution.
They discovered that those with eating disorders had
widespread alterations in the structure of brain pathways governing
taste-reward and appetite regulation. The alterations were found in the white
matter, which coordinates communication between different parts of the brain.
There were also major differences in the role the
hypothalamus played in each group.
Among those without an eating disorder, brain regions
that drive eating took their cues from the hypothalamus.
In the groups with an eating disorder, the pathways to
the hypothalamus were significantly weaker and the direction of information
went in the opposite direction. As a result, their brain may be able to
override the hypothalamus and fend off the signals to eat.
“The appetite region of the brain should drive you off
your chair to get something to eat,” said Frank. “But in patients with anorexia
or bulimia nervosa that is not the case.”
According to the study, humans are programmed at birth
to like sweet tastes. But those with eating disorders begin to avoid eating
sweets for fear of gaining weight.
“One could see such avoidance as a form of learned
behavior and more specifically operant conditioning, with weight gain as the
feared `punishment,’’’ the study said.
This behavior could eventually alter the brain
circuits governing appetite and food intake. Researchers now suggest that being
afraid to eat certain foods could impact the taste-reward processing mechanisms
in the brain which could then reduce the influence of the hypothalamus.
“We now understand better on the biological level how
those with an eating disorder may be able to override the drive to eat,” said
Frank. “Next we need to begin looking at children to see when all of this
starts to come into play.”
Frank is the author of a new book entitled “WHAT
CAUSES EATING DISORDERS – AND WHAT DO THEY CAUSE?”
available on Amazon and other outlets.