Scientists have discovered that in overweight people, the brain’s pleasure center may not experience satiation causing some to compensate by overeating.

The brain’s sluggish reaction to food may be caused by a shortage in the amount of nerves that respond to dopamine, the brain chemical that senses pleasure and has the ability to control impulses. The presence of Taq1A1, a gene that is linked to the body having fewer dopamine receptors, may also be the cause.

“This paper takes it one step farther,” says Nora Volkow, MD, a dopamine specialist and Director of the National Institute of Drug Abuse. “It takes the gene associated with greater vulnerability for obesity and asks the question why. What is it doing to the way the brain is functioning that would make a person more vulnerable to compulsively eat food and become obese.”

Research results showed that a dopamine-rich area of the brain was far less active in those who were overweight and those who carried the Taq1A1 gene. Also, women who had the gene were more likely to gain weight over time. Researchers hope to determine which children carry the at-risk gene so they can encourage them to take part in recreational sports and eating healthy foods earlier in their lives.