Next, the researchers looked for differences within the monozygotic twin pairs, who essentially share a genome. They compared the brain activation of the twin with the higher fat mass with that of the twin with lower fat mass. Instead of seeing the same correlation between higher adiposity and greater brain activation with tempting stimuli, “Suddenly, we lost that relationship between how many calories they would eat and how their brain activated with the food,” said Dr. Rosenbaum. This is a clue, she said, that genetics, rather than simple adiposity, is driving the different responses to food cues.
The study was funded by the National Institutes of Health. Dr. Rosenbaum reported no financial disclosures.