A New Clue to the Link Between Dopamine Receptors and Weight Problems

Science has been searching for the connection between weight problems and our brains for a long time now. New research points to a gene that could prod people to overeat and gain weight. The most recent findings indicate that obese people seem to have fewer dopamine receptors in the brain... giving them less of an ability to feel pleasure in eating and encouraging them to eat more to get the same pleasure.

The research used magnetic resonance imaging (MRI) scans of the pleasure centers of the brain in a group of 53 female university students and 33 teenage girls, looking at the response to food. Subjects were given sips of a chocolate milkshake, and then a tasteless solution. Participants were also checked for the presence of a genetic variant called Taq1A1, linked to a lower number of dopamine D2 receptors in the brain. The body mass index of the subjects was then tracked for one year.

At the end of the follow up, researcher found that subjects whose brain was less activated by the chocolate milkshake and who had the gene variant, were also most likely to have gained weight during the year of follow up. The increase was 3.6%. "This is the first imaging study which found less activation of dopamine receptors in [some] humans," said study lead author Eric Stice, a scientist at the Oregon Research Institute in Portland.

Dopamine is a neurotransmitter that gets released when you eat... bringing that feeling of pleasure. In our distant past, this "pleasure chemical" was a reward to the body for eating a life sustaining meal. The amount of dopamine released is related to the level of pleasure experienced, and it seems that some of us are just genetically predisposed to not have the number of dopamine receptors we need.

Earlier work has shown that obese individuals tend to have fewer D2 receptors than leaner people. This may explain why some can eat anything they want and not gain... and others feel they eat normally and still gain.

This latest work is the result of a collaboration between clinical psychologists from Oregon Research Institute and the University of Texas, and sensory neuroscientists from the John B. Pierce Laboratory and the Yale University School of Medicine. The research was funded by a grant (R1MH64560A) from the National Institutes of Health Roadmap for Medical Research.

"What is new here is that for the first time they have identified the consequences of this genetic polymorphism (type) in how the brain functions," said Dr. Nora Volkow who has worked to identify the role of the D2 gene (the one missing in the ORI subjects) in overeating. Now the director of the National Institute on Drug Abuse, she's worked hard to make the link between addictive behaviors and the human brain. She also makes the connection between lack of dopamine receptors and other abusive behaviors, instances of people doing things like drinking and drugs compulsively, even when they know better.

And while you can't change the genetics of your brain right now, there are things you can do to help yourself fight back against weight problems. Eating a healthy diet, and consuming meals more slowly are important first steps. You'll also want to be sure you're active - getting two to three workouts per week - to help activate the dopamine pathway and reduce the urge to overeat.