fMRI reactivity on a delay discounting task predicts weight gain in obese women

Obesity can be accompanied by abnormalities in executive function and related neural circuitry. A useful task for studying executive function is delay discounting (DD), in which an individual chooses between sooner and delayed, but greater, amounts of money or other commodities. We previously found that obese compared to normal-weight women made more immediate choices on a monetary DD task, or had greater delay discounting. In the present study, we performed functional magnetic resonance imaging (fMRI) of obese women during performance of a DD of money task. Confirming the results of previous studies, we found that more difficult compared to easy DD trials resulted in activation in putative executive function areas of the brain, the middle and inferior frontal gyri, and medial prefrontal cortex. Most interestingly, we also found that less activation in executive function areas such as the inferior, middle, and superior frontal gyri on difficult vs. easy DD trials predicted a greater rate of weight gain over the subsequent 1.3-2.9 years. These results suggest that suboptimal functioning of executive function areas such as prefrontal cortex contributes to the progression of obesity.