Blunted brain activity may spur obesity

When we bite into a favorite food, our pleasure is underscored by a rush of the neurotransmitter dopamine in the reward circuits of the brain. However, a new study shows that this reward response is blunted in obese individuals.

As reported in the October 17 issue of Science, Dana Small, Ph.D., assistant professor of psychiatry, and collaborators gave women samples of a chocolate milkshake while measuring their brain activity. The neural response to the treat was significantly dampened in subjects with a higher body mass index, and especially diminished in subjects carrying a genetic variation associated with lower numbers of dopamine receptors. These latter subjects were also more likely to gain weight over the course of a year. “Our study is exciting,” says Small, “because it demonstrates an association between an abnormal response to food and future weight gain—and it shows that this relationship depends upon your genetic makeup.”