Finally, participants were given access to a buffet meal and allowed to eat as much as they chose; consumption was measured. Before and after each meal and scan, and at various points during the day, the investigators also obtained blood samples and asked participants to rate their hunger on a visual analog scale.
“When compared with how much fat mass they had, there was no relationship between how hungry or full they were when they were fasting, how hungry or full they were with a snack, or when they ate the buffet. It just didn’t matter how much fat mass they had” for subjective reporting of hunger and fullness, said Dr. Rosenbaum.
However, there was a direct correlation between fat mass and amount consumed at the ad libitum buffet. Additionally, the fMRI analysis showed that “the brain activation that we would expect to go down, didn’t seem to go down as much if you had more adiposity,” she said.
As fat mass went up, areas of the brain implicated in appetite and reward showed more activity when participants were presented with the tempting images of high calorie foods, regardless of the calories consumed. These areas include the ventral and dorsal striata, the amygdala, the insula, the ventral tegmental area, and the medial orbitofrontal cortex.