UPTON, NY — A brain imaging study at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory reveals a subtle difference between ordinary obese subjects and those who compulsively overeat, or binge: In binge eaters but not ordinary obese subjects, the mere sight or smell of favorite foods triggers a spike in dopamine — a brain chemical linked to reward and motivation. The findings — published online on February 24, 2011, in the journal Obesity — suggest that this dopamine spike may play a role in triggering compulsive overeating.
“These results identify dopamine neurotransmission, which primes the brain to seek reward, as being of relevance to the neurobiology of binge eating disorder,” said study lead author Gene-Jack Wang, a physician at Brookhaven Lab and the Mount Sinai School of Medicine. Previous studies conducted by Wang’s team have identified a similar dopamine spike in drug-addicted individuals when they were shown images of people taking drugs, as well as other neurochemical similarities between drug addiction and obesity, including a role for dopamine in triggering desire for drugs and/or food.
Food stimulation with methylphenidate significantly increased dopamine levels in the caudate and putamen regions of the brain in binge eaters but not in the non-binge eaters. Subjects with the most severe binge eating disorder, as assessed by psychological evaluations, had the highest dopamine levels in the caudate.
Dopamine levels did not rise significantly in other brain regions or under any other condition (neutral stimulation with or without methylphenidate, or food stimulation without methylphenidate) in either group, and were not correlated with body mass index of the research subjects. Assessments of the levels of receptors for dopamine also did not differ between the two groups.
“So the key difference we found between binge eaters and non-binge eating obese subjects was a fairly subtle elevation of dopamine levels in the caudate in the binge eaters in response to food stimulation,” Wang said.
“This dopamine response is in a different part of the brain from what we’ve observed in studies of drug addiction, which found dopamine spikes in the brain’s reward center in response to drug-associated cues. The caudate, in contrast, is believed to be involved in reinforcement of action potentially leading to reward, but not in processing of the reward per se. That means this response effectively primes the brain to seek the reward, which is also observed in drug-addicted subjects,” Wang said.
Inasmuch as binge eating is not exclusively found in obese individuals, the scientists believe further studies are warranted to assess the neurobiological factors that may differentiate obese and non-obese binge eaters.
This study was funded by the National Institutes of Health through the Intramural Program of the National Institute on Alcoholism and Alcohol Abuse and the General Clinical Research Center of Stony Brook University, using infrastructure supported at Brookhaven Lab by DOE’s Office of Science.
Read the full report here: http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=1233&template=Today