August 10, 2011

Why You Overeat

Three neurobiological processes underlie overeating. What do they tell us about how to stop?

Overweight people often carry the stigma of being "lazy" or not strong enough to resist temptation. But there’s a lot of evidence to suggest that this is a misguided concept. With obesity reaching epidemic proportions, understanding how it works behaviorally and in the brain is important — and now a team of researchers has outlined the three neurobiological processes that underlie how overeating actually works.

We tend to prefer short term rewards (like chocolate cake now) over long term rewards (like losing weight or becoming healthier overall). This process is involved in many addictions.

In the new paper, the team begins by explaining why the current tack that weight loss counselors take to encourage patients to lose weight can actually be detrimental. Suggesting that weight loss is all about personal choice and resisting temptation can lead to "guilt and stigmatization," rather than motivation, in the patient.

Instead they suggest that overeating should be understood in neurobiological terms, and explain the three processes that underlie the behavior.

One process is the brain’s reward circuit, which is involved in many addictions and involves the brain chemical dopamine. This circuit is responsible both for the pleasurable feeling (reward) one gets when eating a satisfying food and for the urge to seek out those foods in the first place. And some people are more sensitive to this mechanism than others.

The second process involves the brain’s prefrontal cortex, which mediates "self-control, planning, and goal-directed behavior." It is also involved in inhibiting one’s urges for "the purpose of self-regulation," as in dieting.

The third circuit that comes into play with overeating is what the authors call "time discounting." We tend to prefer short term rewards (like chocolate cake now) over long term rewards (like losing weight or becoming healthier overall). This process is involved in many addictions: "For some individuals and not others, the immediate rewards of smoking, gambling, and drug use have a more potent influence on decision-making than the long-term social, financial, and physical costs of such behavior."

On a practical level, the authors write that "emphasizing genetically-influenced neurobiological processes that confer vulnerability to overeating in a toxic food environment, the model enables dietetics practitioners to more effectively address obesity… without promoting stigma." In simpler terms, counselors can help patients more by stressing the biological bases for overeating, rather than emphasizing the behavioral side of it, which tends to invoke "character flaws (eg, lack of willpower)." It will be interesting to see how this and other studies on the neurobiology of overeating change the way we view overeating and obesity.

This research took place at the Rush University Prevention Center, and was published in the August 2011 issue of the Journal of the American Dietetic Association.

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