New Genetic Risk for Obesity continued...
"Of course it is a vicious circle," says Pothos. "A person says, 'I do not get pleasure from high-energy food, so I am eating even more but getting less pleasure, I don't know what to do. So obesity and weight gain may result from what we may call addiction to high-energy food."
The term "addiction" isn't a metaphor. Stice and Pothos note that the same vicious circle, involving the same brain circuits and the same underlying genetic susceptibility, occurs in people addicted to drugs.
However, both researchers are quick to point out that a dysfunctional pleasure system is only half the answer to the puzzle of obesity. Metabolic functions that control body weight also play a major role.
"We don't want to say obesity is an addictive disorder and not a metabolic disorder. We just want to say, 'Pay attention to both,'" Pothos says.
Stice is now looking at whether obese people who switch to a healthy diet can reset their pleasure circuitry. He finds that when obese people stop eating energy-dense foods, their craving for such foods goes down, not up.
"If we can get obese people to improve the quality of their diets and stay the course for long time, eventually they do much better in craving and their pleasure circuits should go back to their old balance," he says.
Pothos and colleagues are looking at whether parents' unhealthy eating behavior has an effect on children -- even before they are born.
"How did the obesity epidemic happen? Something is passed from parents to their offspring," he suggests.
Stice and colleagues report their findings in the Oct. 17 issue of the journal Science. Stice's colleagues included researchers from Yale University and the University of Texas at Austin.