Scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory (BNL) conducted a study to differentiate obese form binge eaters. The sight or smell of favorite foods triggers a spike in dopamine in binge eaters, but not in the "normal" obese. The findings are published online in the journal Obesity and suggest that the dopamine spike may play a role in triggering compulsive overeating.
The main scientists, Dr. Gene-Jack Wang, said:"These results identify dopamine neurotransmission, which primes the brain to seek reward, as being of relevance to the neurobiology of binge eating disorder." A similar dopamine spike has been shown in drug addicts' brains when shown images of drugs. Wang said that dopamine spikes were associated with people feeling a pike in hunger.
The subjects were 10 obese people with a clinical diagnosis of binge eating disorder, based on evaluations at St. Luke's-Roosevelt Hospital, and 8 non-binging obese subjects. The scientists used positron emission tomography (PET) to scan the subjects' brains after injecting a radiotracer designed to bind to dopamine receptors in the brain. Subjects fasted for 16 hours prior to the study. They were scanned 4 times in 2 days. Heated food, which subjects could taste with swabs, made up the food stimulation condition. For the neutral stimulation scans, non-food-related pictures and inanimate objects such as toys were displayed for subjects to see and smell.
The subjects who had the highest binge eating levels also experienced the highest dopamine spikes. The amount of dopamine receptors between the two groups did not differ significantly. Dompamine spikes were present in the caudate region of the brain, which is involved in the in reinforcement of action potentially leading to reward, but not in processing of the reward.
"That means this response effectively primes the brain to seek the reward, which is also observed in drug-addicted subjects," Wang said.
In contrast, dopamine spikes in drug addicts were found in the brain's reward center.
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