New research to better understand and treat eating disorders has determined that the brains of people with anorexia and obesity are wired differently.
In the studies, neuroscientists discovered a variety of brain activity across a spectrum of eating behaviors — from extreme overeating to food deprivation. This variation in neurological response influences both the development of an eating disorder and the way in which we respond to a weight loss program.
Eating disorders have the highest mortality rate of any mental illness. Currently, more than two-thirds of the U.S. population are overweight or obese — a health factor associated with cardiovascular issues, diabetes, and cancer.
“This body of work not only increases our understanding of the relationship between food and brain function but can also inform weight loss programs,” said Laura Martin, Ph.D., one of several researchers whose work being presented at a meeting of cognitive neuroscientists in Chicago.
“One of the most intriguing aspects of these studies of the brain on food,” Martin said, is that they show “consistent activations of reward areas of the brain that are also implicated in studies of addiction.”
However, how those reward areas respond to food differs between people depending on their eating behaviors, according to the new brain imaging study by Laura Holsen of Harvard Medical School and Brigham and Women’s Hospital and colleagues.
Holsen’s team conducted fMRI brain scans of individuals with one of three eating conditions — anorexia nervosa, simple obesity, and Prader-Willi syndrome (extreme obesity) — as well as healthy control subjects.
When hungry, those with anorexia, who severely restrict their food intake, showed substantially decreased responses to various pictures of food in regions of their brains associated with reward and pleasure. For those who chronically overeat, there were significantly increased responses in those same brain regions.
“Our findings provide evidence of an overall continuum relating food intake behavior and weight outcomes to food reward circuitry activity,” Holsen says.
Holsen believes her findings are relevant for everyday eating decisions in healthy individuals. “Even in individuals who do not have eating disorders, there are areas of the brain that assist in evaluating the reward value of different foods, which in turn plays a role in the decisions we make about which foods to eat.”
In a related research effort, Kyle Simmons of the Laureate Institute works with fMRI scans to determine the brainâ€™s response when an individual sees food.
The brain scans show an apparent overlap in the brain region called the insula that responds to seeing food pictures, and the region of the insula that processes taste, the “primary gustatory cortex.”
Simmons is currently expanding this work to better understand the differences in taste preferences between lean, healthy individuals and obese ones. “We simply don’t know yet if differences exist between lean and obese participants,” he says.
“And knowing which brain regions underlie inferences about food taste and reward is critical if we are going to develop efficacious interventions for obesity and certain eating disorders, both of which are associated with enormous personal and public health costs.”