This question was asked by Rachel Goldman PhD and her research group from New York University. To provide an answer, they conducted a study on 40 individuals who underwent MRI brain imaging after having received bariatric surgery for obesity.
According to Goldman, clinical experience with patients who receive bariatric surgery shows that some patients lose less weight than what was expected, and others may actually gain weight back after their surgery, although most patients do lose weight. Until now, there was no clear understanding of what causes this differential response.
In this study, brain scans after surgery showed the difference between patients who did lose a significant amount of weight and those who did not was a different pattern of neural responsiveness to food cues in several sections of the brain. The interpretation by Goldman of these data was that patients who are successful in losing weight demonstrate a resistance to craving for food. She commented, “obese individuals may have heightened arousal to food cues.”
More support for this idea would come from doing a repeat experiment similar to the one described, but looking at arousal patterns in the brain before and after bariatric surgery, to see if the surgery changes these patterns at all.
Source: MedPage Today