The Clinical Hour

Through a basic understanding of human behavior, Freud coined the term Pleasure Principal which he understood as our natural drive to seek pleasure and to avoid pain. Today’s research shows that not only do we seek pleasure but we do it despite pain.

A recent study found that our brains deteriorate the same way when we overeat just as it would if we were addicted to a drug. Researchers at the Scripps Research Institute tested this hypothesis with rats. They separated the rats into three groups. They gave one group an all you can eat buffet that included nutritional food as well as foods high in fat and other deliciousness (officially referred to as calorically dense food). The second group had limited access to the buffet of goodies. A third group was fed a balanced meal. After a period of time, the researchers even began to punish the rats for eating the non-nutritious food however the rats kept choosing the non-healthy food over the healthy options. Researchers observed that the more bad food the rats ate, the less likely they would choose nutritious food. This resulted in a tripling of their necessary caloric intake. The limited buffet access group only consumed 66 percent of their daily nutritional requirements, and a whopping 5 percent for the unlimited access group despite the over-consumption of food.

As this became a daily habit for the rats, researchers measured brain activity (particularly dopamine d2 receptors). The study shows that as these rats became obese, there was a progressive deterioration with the pleasure centers in the brain (the replica of neuroscience’s understanding of how drug addiction occurs). So as those pleasure centers become less responsive, consumption of fatty foods increase. Paul Kenny, lead researcher says “The body adapts remarkably well to change — and that’s the problem. When the animal over stimulates its brain pleasure centers with highly palatable food, the systems adapt by decreasing their activity. However, now the animal requires constant stimulation from palatable food to avoid entering a persistent state of negative reward.”

Neuroscientist studied this phenomenological comparison (substance abuse and overeating) by measuring what science has explained as the reason for experiences of “being high.” Dopamine is a chemical in the brain that is associated with feeling good and is naturally released during pleasurable experiences. D2 receptors are the regulators of how much Dopamine should be floating around. When someone uses a drug such as cocaine, D2 is prohibited to regulation Dopamine so that it fills the brain, creating an intense pleasurable experience. After a period time in which dopamine has ran high and wild, the drive increases to subdue D2 receptors to maintain and attempt to achieve the previous high. For example, when the researchers in this study took away the all you can eat buffet from the chubby rats and offered them regular rat chow, they refused to eat for so long they almost starved.

Kenny explains, the reward pathways in the brain have been so over stimulated that the system basically turns on itself, adapting to the new reality of addiction, whether its cocaine or cupcakes. He goes on to say “These data are, as far as we know, the strongest support for the idea that overeating of palatable food can become habitual in the same manner and through the same mechanisms as consumption of drugs of abuse.”

Source: Nature Neuroscience
Published online ahead of print, doi: 10.1038/nn.2519
“Dopamine D2 receptors in addiction-like reward dysfunction and compulsive eating in obese rats”
Authors: P.M. Johnson, P.J. Kenny
A full copy of the paper is freely available here.

Written by:  Julie Barbour,  LCSW owner and founder of Clinical Hour, LLC

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