Overeating and Drug Addiction Share Molecular Mechanisms

Nutritionists have for a long time been drawing attention to the fact that overeating is one of the main drivers of obesity. People who do not know when to stop nibbling on various types of sodas and snacks, and who continue eating even after their stomach is full, are at a much higher risk of developing the condition, which can in turn favor the development of type II diabetes and other disorders. Scientists have been trying to find out what molecular mechanisms drive this urge to overeat, and they learned that the pathways the brain used were the same as the ones involved in drug addiction.

In the new study, the team, based at the Scripps Research Institute (SRI), basically shows that overeating acts like an addiction. The work, which was conducted by SRI associate professor Paul J. Kenny and his graduate student Paul. M. Johnson, is detailed in a new paper, appearing in the March 28 advanced online issue of the esteemed scientific publication Nature Neuroscience. Details of the research were first presented in October 2009 in Chicago, at a meeting of the Society for Neuroscience.

Though many news outlets covered the connection at the time, the work presented last year was only the abstract to the paper. Now published, the work reveals all of its methods, and the experiments it used. The SRI scientists show how lab rats experience a progressively-deteriorating balance in the levels of chemicals that govern their feelings of reward. The group also demonstrated that the brain circuits involved in this were changed as well, just like they were in the case of people taking drugs such as cocaine, ScienceDaily reports.

The data appear to lend more credence to what obese people have been saying for quite some time, and namely that addiction to junk food is just as difficult to get rid off as addiction to hard drugs. When the reward circuit experiences modifications in the brain, compulsive overeating habits are a direct consequence, at least in lab mice. This implies that junk food is indeed addictive. It took the SRI team about three years to conduct all the experiments needed to validate these results.

“The new study, unlike our preliminary abstract, explains what happens in the brain of these animals when they have easy access to high-calorie, high-fat food. It 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,” Kenny says.