Scientists have uncovered the brain circuits that may underlie binge eating disorder and related conditions. The neural wiring is the same as that tied to psychiatric conditions such as drug addiction and obsessive-compulsive disorder.
The work could lead to new ways to understand and treat eating disorders, says Rebecca Boswell, a clinical psychologist at Princeton University who was not involved with the study. Indeed, she says, some of the same drugs and strategies that seek to reverse detrimental habits in other compulsive disorders might work for binge eating.
About one in every 80 women and one in 250 men binge eat in the United States. They devour large quantities of food in one sitting (even if they’re full and it causes discomfort), they often do it alone, and they have a hard time stopping. In another form of binge eating, bulimia nervosa, people don’t keep the food down; they force themselves to expel it via vomiting or laxatives. Both disorders typically begin in early adulthood, yet scientists don’t know exactly what changes in the brain cause them.
Scientists have wondered whether binge eating is an extreme habitual behavior—an automatic, repetitive action that continues regardless of whether the desired outcome is achieved, like drug addiction and other compulsive behaviors. In habitual behaviors, instead of being driven by a goal, such as eating to feel full, an action is driven by external factors or emotions, such as feeling sad.
In the new study, Stanford University scientists recruited women from their Northern California community and used criteria from the Diagnostic and Statistical Manual of Mental Disorders—the gold standard for psychiatric diagnoses—to determine whether they had either binge eating disorder or bulimia. Then the researchers examined their brain activity using functional magnetic resonance imaging (fMRI).
The scientists saw stronger connections between two brain regions—the sensorimotor putamen and the motor cortex, which are involved in promoting habits and making decisions regarding body movements, respectively—than in individuals without eating disorders, they report today in Science Translational Medicine. Connections between the sensorimotor putamen and the anterior cingulate cortex, which is involved in emotion regulation, among other things, and is also implicated in habit learning, were weaker. Similar patterns have been seen in individuals with drug addiction and compulsive disorders such as hoarding and excessive hand washing.
The findings make sense given that researchers have suspected both binge eating and bulimia are compulsive habits, says co-author Allan Wang, a medical student. “It fits nicely with what we think that these circuits should be doing.”
Another brain scanning method, positron emission tomography, revealed something else: In the people with eating disorders, the fewer receptors they had for the neurotransmitter dopamine, which plays a critical role in reward and habit learning, the more likely they were to engage in binge eating behaviors. This suggests pharmacological treatments that target dopamine in the sensorimotor putamen could help combat these conditions, Boswell says.
An approved drug for binge eating disorder called Vyvanse works by increasing the levels of dopamine throughout the brain. “This research would support the use of similar classes on medication for binge eating disorders,” Boswell says. Vyvanse can only be used for short periods of time because of its addictive potential, she notes, underlining the need for alternatives.
Given that the study was only conducted on women, scientists will need to repeat the work on men, Boswell says. She says it’s also unclear whether the brain circuitry the team identified causes these eating disorders, or the disorders themselves alter the brain circuitry. “Is it the chicken or the egg?”
Wang and his colleagues hope to explore this next. They also want to see whether the same brain circuits are involved in eating disorders more broadly, including in anorexia. “[This study] opens up further areas of investigation that we can look into,” Wang says. -science.org
