Study: Brain activity on fMRI can predict weight gain, sexual desire

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Overeating, drug addiction relapses and impulsive sexual behavior may have a deeper cause than a simple lack of will power. Researchers have demonstrated a connection between brain responses to food and sexual images measured on functional MRI (fMRI), suggesting heightened reward responsivity may contribute to overeating and sexual activity, according to a study published April 18 in the Journal of Neuroscience.

“The implication of the current research is that there are individual differences in the extent to which cue exposure primes behavior, such that some individuals show more robust reward activity to appetitive cues, which in turn may produce greater behavioral priming,” wrote authors Kathryn E. Demos, PhD, and colleagues from Dartmouth College in Hanover, N.H.

Using fMRI, Demos and colleagues targeted the nucleus accumbens, the brain’s “reward center,” in a cohort of incoming first-year female college students. Fifty-eight were scanned while viewing images of animals, environmental scenes, appetizing food and images of people, some of which were sexual scenes. Participants were weighed and told that it was a necessary part of the scanning procedure.

Six months later, 48 study participants returned, with 10 lost to follow-up. Those who returned were weighed again and asked to complete a questionnaire assessing their sexual behavior.

Results showed that activity in the left nucleus accumbens correlated positively with body mass index (BMI) change. “Importantly, this relationship was unique to the food images. [Nucleus accubens] activity in response to the non-food images did not predict weight gain,” wrote the authors.

Similarly, brain activity when viewing sexual images was positively correlated with sexual desire, while non-sexual image response was not predictive of sexual desire.

"This is one of the first studies in brain imaging that uses the responses observed in the scanner to predict important, real-world outcomes over a long period of time," Todd Heatherton, PhD, a coauthor on the study, said in a statement. "Using brain activity to predict a consequential behavior outside the scanner is pretty novel."

The researchers noted that the first step toward controlling cravings is to become aware of how much they are affected by triggers in the environment. "You need to actively be thinking about the behavior you want to control in order to regulate it," said William M. Kelley, PhD, coauthor. "Self-regulation requires a lot of conscious effort."