The brain reward systems of women with anorexia may work differently from those of women who are obese, a new study suggests.
Researchers from the University of Colorado School of Medicine found that women who are anorexic have sensitized brain reward circuits, while women who are obese have desensitized brain reward circuits.
"It is clear that in humans the brain's reward system helps to regulate food intake," study researcher Dr. Guido Frank, M.D., assistant professor director of the Developmental Brain Research Program at the University of Colorado School of Medicine, said in a statement. But "the specific role of these networks in eating disorders such as anorexia nervosa and, conversely, obesity, remains unclear."
The study, published in the journal Neuropsychopharmacology, included 63 women who were either obese or anorexic. The researchers conducted fMRI brain scans on them, as well as on women of normal weight.
The researchers conditioned the study participants to look at shapes and then link those shapes with either a sweet-tasting liquid or a nonsweet-tasting liquid. Then, the participants were given either the sweet or nonsweet liquids as the researchers looked at their brain activity.
In the women who were anorexic, the reward systems in their brains had higher neural activation. Meanwhile, in women who were obese, the brain reward systems had lower neural activation.
Previously, a 2008 study in mice in the FASEB Journal showed that there is an association between problems with brain signaling for dopamine -- the chemical messenger in the brain linked with pleasure -- and obesity.
"Baseline dopamine levels were 50 percent lower and stimulated dopamine release was significantly attenuated in the brain reward systems of obesity-prone rats, compared with obesity-resistant rats," study researcher Emmanuel Pothos, Ph.D., an assistant professor in pharmacology at Tufts University School of Medicine, said in a statement.
Pothos added that other studies have shown that when you eat food, the brain releases more dopamine to the brain circuits that "mediate the pleasurable aspects of eating." Similarly, when the body doesn't get enough food and therefore experiences a decrease in weight, dopamine levels go down.
"Therefore, increased food intake may represent a compensatory attempt to restore baseline dopamine levels," Pothos said in the statement.