As we may become addicted to thoughts and behaviors, scientists now believe we can become addicted to foods, which may partially explain the global obesity epidemic.

Canadian researchers reported Wednesday that high-fructose corn syrup may cause behavioral reactions in rats similar to those induced by drugs such as cocaine. Addiction expert Francesco Leri, an associate professor of neuroscience and applied cognitive science at the University of Guelfph, presented the findings at a meeting held in Toronto by the Canadian Association for Neuroscience.

The "Food Addiction" theory builds on recent evidence showing similarities between gluttonous consumption of unhealthy foods and traditional addictive behaviors, such as continued drug or alcohol use despite adverse consequences. Neurobiological research, too, has revealed parallels in the way the brain responds to drugs of abuse and foods that delight the palate. Now, animal studies showing the same are leading researchers to think certain types of food may sometimes trigger addictive processes in those genetically susceptible.

The Yale Food Addiction Scale, developed last year by researchers at Yale University, attempts to quantify the degree to which people become addicted to foods such as soda, ice cream, white bread, and bacon.

To test the theory, Leri studied the response of rats to foods that were artificially pumped with high concentrations of sugar, fats, and taste enhancers such as high-fructose corn syrup, in addition to products like Oreo cookies. He found that not all rats took the bait.

Just as with humans, the availability of unnaturally sweetened and enhanced foods — or drugs of abuse — doesn't necessarily lead to addiction. Only a small percent of people who try cocaine become addicted, after all. "We have evidence in laboratory animals of a shared vulnerability to develop preferences for sweet foods and for cocaine," Leri said.

Susceptibility to addiction to food and cocaine alike might be genetically-based. Leri analyzed the behavioral, chemical, and neurobiological changes observed in rats by consumption of "addictive foods, looking for makers of vulnerability to high-fructose corn syrup."

"We are not rats, but our children do not think too much about the impact of sweets on their brain and behavior," he said. "There is now convincing neurobiological and behavioral evidence indicating that addiction to food is possible."

Leri said the research team hoped to discover the biological predictors of susceptibility to high-fructose corn syrup, with an eye on developing possible preventive treatments for people at risk of obesity and associated health ailments.

The findings may lead to drug therapies for some of the 1.4 billion people worldwide who are classified as overweight, of whom 500 million are obese — more than double the number since 1980.