A new report shows that the same molecular mechanisms that drive some of the same brain changes that occur in the drug addicts may also take place in people who overeat.
The scientists fed the rats a diet of modeled after the type that contributes to human obesity--easy-to-obtain, high-calorie, high-fat foods like sausage, bacon, and cheesecake. These animals gained weight quickly.
Study co-author Paul J. Kenny explains that the study “presents the most thorough and compelling evidence that drug addiction and obesity are based on the same underlying neurobiological mechanisms. In the study, the animals completely lost control over their eating behavior, the primary hallmark of addiction. They continued to overeat even when they anticipated receiving electric shocks, highlighting just how motivated they were to consume the palatable food.”
“They always went for the worst types of food,” says Kenny, “and as a result, they took in twice the calories as the control rats. When we removed the junk food and tried to put them on a nutritious diet—what we called the ‘salad bar option’—they simply refused to eat. The change in their diet preference was so great that they basically starved themselves for two weeks after they were cut off from junk food. It was the animals that showed the ‘crash’ in brain reward circuitries that had the most profound shift in food preference to the palatable, unhealthy diet. These same rats were also those that kept on eating even when they are anticipated being shocked.”
Specifically the scientists found that overeating junk food reduces dopamine D2 receptors, a mechanism which also plays a key role in cocaine and heroine addiction.
Nature neuroscience--March 28, 2010