Differences in brain chemistry between people who are obese and those who are not may help explain what triggers overeating in response to food cues such as the aroma of popcorn at the movies. To arrive at this conclusion, researchers at the National Institutes of Health (NIH) looked at 43 men and women with varying amounts of body fat. The investigators found that, compared to the study’s lean participants, those who were obese tended to have more dopamine activity in the brain’s habit-forming region and less activity in the brain area controlling rewards. (Dopamine is a chemical messenger in the brain that influences reward motivation and habit formation.) The finding suggested that the brain differences observed might result in obese people being more susceptible to environmental food cues than those who are lean. At the same time, the action of dopamine in other areas of the brain may make food less rewarding to the obese. During the study, all participants were on the same eating, sleeping and activity schedule. The researchers determined the tendency to overeat from the participants’ responses to detailed questions and to PET (positron emission tomography) scans that looked at sites in the brain where dopamine action can occur. The study didn’t prove cause and effect but did reveal a link between dopamine activity and the urge to overeat.
Kevin D. Hall et al “Striatal dopamine D2-like receptor correlation patterns with human obesity and opportunistic eating behavior.” Molecular Psychiatry, 2014; DOI: 10.1038/mp.2014.102