PORTLAND, Ore., March 26 (UPI) -- Weight gain produced a blunted response to intake of a chocolate milkshake, suggesting overeating may lead to reduced reward from food, U.S. researchers say.
Eric Stice of the Oregon Research Institute and colleagues including Dana Small from the J.B. Pierce Laboratory in New Haven, Conn., used functional magnetic resonance imaging to compare the neural response to food and monetary reward in lean adolescents at risk for obesity.
The study involved 60 lean adolescents -- high-risk teens were children of two obese or overweight parents, while the low-risk teens had two lean parents. Adolescent children of obese vs. normal-weight parents show a fourfold increase in risk for obesity onset.
"The findings are surprising," Stice says in a statement. "They suggest that the initial vulnerability for overeating may be hyper-responsivity of reward circuitry to food intake. The fact that the same reward regions in the brain showed greater response to monetary reward is novel and implies that individuals at risk for obesity show greater responsivity to reward in general."
The findings seem to challenge the widely accepted theory that it is a reward deficit -- fewer dopamine receptors in the brain -- that increases vulnerability to overeating, Stice says.
The study, published in The Journal of Neuroscience, also found that at-risk youth for obesity showed hyper-responsivity of somatosentory regions to food intake, which plays a key role in sensing the fat content of food suggesting people who are particularly sensitive to detecting high-fat foods may be at unique risk for overeating.