• Tue, Sep 20 2011

Junk Food Photos Elicit Different Responses in Brains of Obese, Non-Obese

There was a time when people thought body-size was all about willpower—control what you eat, exercise, and you’ll be thin; over-indulge or sloth around, and you won’t. Of course, we know now that it’s much more complicated than that—so many other factors, like genetics, metabolism, environment and the type of calories consumed (to name just a few) play a role in weight and body size. Lately, however, researchers have been coming back to the issue of ‘self-control’ in weight management—only this time, scientists are looking at its biological basis.

Maybe lack of impulse control does play a role in why some people are overweight seems to be the thinking, but it’s no longer seen as some sort of moral failing. Instead, it’s explained via differences in obese individuals’ brain chemistry or structure. Publishing in the Journal of Clinical Investigation, researchers from Yale University and the University of California explained how, in a study of five obese and non-obese patients, pictures of high-calorie foods stimulated increased activity in the area of the brain associated with reward in all subjects when their blood sugar levels were low. When blood sugar was normal, however, non-obese patients viewing the fatty-food photos showed increased activity in the prefrontal cortex—the part of the brain associated with impulse control; obese patients exhibited no such prefrontal action. This is just one small study, of course. But this past summer, German neuroscientists found similar results—obese women show structural differences in the brain regions linked to impulse-control compared to woman with normal-range BMIs.

What does it all mean? I don’t think anyone’s quite sure. Do these differences in brain activity and structure cause some people to become obese? Or are they a response to accumulative diet differences on the brains of obese individuals? And doesn’t it somehow feel very un-PC to say obese people react differently to pictures of cheeseburgers? I know science has no regard for political correctness—but science has also been known, at times, to conform to the expectations of the researchers. Think of all those evolutionary psychology and/or neuroscience studies showing how women are just innately better at doing grocery shopping and laundry …

Perhaps more important than the differences between obese and non-obese patients in this most recent study are the similarities: Everyone was more susceptible to craving bad foods when blood sugar was low. That’s more evidence that the best way to resist unhealthy food binges is to not let your blood sugar get low in the first place—in other words, to eat healthy snacks between meals or throughout the day, and avoid high-sugar, high-carb foods that will lead to blood sugar spikes and then crashes.

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