Junk food addiction may be clue to obesity: study

The findings in a study of animals cannot be directly applied to human obesity, but may help in understanding the condition and in developing therapies to treat it, researchers wrote in the journal "Nature Neuroscience."

The study, involving rats, found that overconsumption of high-calorie food can trigger addiction-like responses in the brain and that high-calorie food can turn rats into compulsive eaters in a laboratory setting, the article said.

The scientists also found decreased levels of a specific dopamine receptor -- a brain chemical that allows a feeling of reward -- in overweight rats, as has been reported in humans addicted to drugs, the article said.

"Obesity may be a form of compulsive eating. Other treatments in development for other forms of compulsion, for example drug addiction, may be very useful for the treatment of obesity," researcher Paul Kenny of The Scripps Research Institute in Florida said in a telephone interview.

Obesity-related diseases cost the United States an estimated $150 billion each year, according to U.S. federal agencies. An estimated two-thirds of American adults and one-third of children are obese or overweight.

For the study, Kenny and colleagues headed to the grocery store.

"We basically bought all of the stuff that people really like -- Ding-Dongs, cheesecake, bacon, sausage, the stuff that you enjoy, but you really shouldn't eat too often," he said.

They also bought healthy foods and devised a diet plan for three groups of rats.

One group ate a balanced healthy diet. Another group received healthy food, but had access to high-calorie food for one hour a day. Rats in the third group were fed healthy meals and given unlimited access to high-calorie foods.

The rats in the third group developed a preference for the high-calorie food, munched on it all day and quickly became obese, Kenny said.

The rats in the experiment had also been trained to expect a minor shock when exposed to a light. But when the rats that had unlimited access to high-calorie food were shown the light, they did not respond to the potential danger, Kenny said. Instead, they continued to eat their snacks.

"What we're seeing in our animals is very similar to what you'd see in humans who overindulge," he said. "It seemed that it was okay, from what we could tell, to enjoy snack foods, but if you repeatedly overindulge, that's where the problem comes in."