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Self-control and weight: reading between the lines

Posted May 03 2009 10:04pm
I first read this article, titled " Mechanisms of Self-control Pinpointed in Brain," after seeing some people mention it on Twitter (are you on Twitter? Click here to follow ED Bites!). Of course, given the population both of who I follow on Twitter and the popular connotations of "self-control," I knew the article would be about obesity and weight loss.

I was right.

The actual science of the research was interesting. The study participants--all self-reported dieters--were asked to rate 50 foods on how good they would taste, and the health benefits of the foods. The researchers selected an "index food," which fell midway on both the tastiness and health benefits scale, and picked one of the other 50 foods at random. The dieters, situated in an fMRI scanner, had to then select and eat either the index food or the random item. According to a press release,

...the researchers were able to pick out 19 volunteers who showed a significant amount of dietary self-control in their choices, picking mostly healthy foods, regardless of taste. They were also able to identify 18 additional volunteers who showed very little self-control, picking what they believed to be the tastier food most of the time, regardless of its nutritional value.

Previous studies have shown that value-based decisions--like what kind of food to eat--are reflected in the activity of a region in the brain called the ventromedial prefrontal cortex, or vmPFC. If activity in the vmPFC goes down, explains Todd Hare, a postdoctoral scholar in neuroeconomics and the first author on the Science paper, "it means the person is probably going to say no to that item; if it goes up, they're likely to choose that item."

In the non-self-controllers, Rangel notes, the vmPFC seemed to only take the taste of the food into consideration in making a decision. "In the case of good self-controllers, however, another area of the brain--called the dorsolateral prefrontal cortex [DLPFC]--becomes active, and modulates the basic value signals so that the self-controllers can also incorporate health considerations into their decisions," he explains. In other words, the DLPFC allows the vmPFC to weigh both taste and health benefits at the same time.

(the links were my addition)

Which, okay, fine. Even aside from the obesity hysteria angle, I do find this idea quite intriguing. I think it would also be very interesting to see how people with eating disorders (clinical and so-called subclinical, recovered and actively ill) would act in this study, whether this "self-control" region would be activated or a fear region or something else entirely.

BUT...

Holy leaping assumptions, Scooby!

First of all, there's the idea that it takes self-control to choose "healthy" foods. The idea that fruits and veggies are gross is typically an idea that accompanies dieting. Some veggies, of course, I wouldn't touch with a ten foot pole (cauliflower). Others, however, are absolutely yummy if cooked right.

Then, there's the idea that people who lose weight have more self-control than people who can't. Conversely, fat people must have no self control at all. Which is total crap. Most dieters desperately want to lose weight, even if they don't want to be a Size Zero. I highly recommend Gina Kolata's book Rethinking Thin to learn more about this. Eye-opening and chock-full of good science and humanity.

There's also the simple fact that humans generally suck at self-control, and that we have a limited amount of self-control to work with. This is likely why dieters exhibit a range of impulsive behaviors that you don't normally see when they aren't dieting.

Lastly, there's the idea that you're "supposed" to ignore how a food tastes when deciding what to eat. I mean, if you eat something because it tastes good, you don't have any self-control (according to the researchers' conclusions). But if you can relax and let go of those values you have attached to foods (Snickers=bad, lettuce=good), perhaps deciding what to eat won't be a matter of self-control. It will be a matter of what tastes good and what does my body need? There are days when I sometimes feel like a candy bar for lunch. But I know this isn't the nutritionally balanced lunch my body needs, so I have something else with it. Or I eat the Snickers as a snack. If you constantly deny your taste buds, there will be hell to pay.
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