Craving Control

It’s easy to train your brain to crave healthy food, a new study shows – all you’ve got to do is learn to pay attention to the right things.

As shown here, the adorable kitty PFC is mostly "nom"-oriented.

When we’re thinking about what to snack on, one particular brain region – the ventral medial prefrontal cortex (vmPFC) – leaps into action, helping us consider which tastes and textures we’d most enjoy. But a neaby region, the dorsolateral prefrontal cortex (dlPFC), lights up when we focus our attention on other aspects of the food, like its protein content, or the pond of grease that surrounds it.

In short, the vmPFC is the frontal cortex’s “nom nom nom” area, and the dlPFC is its “for your health!” area.

The study, which was published in the Journal of Neuroscience, says this data makes a lot of sense, because we already know that the dlPFC’s modulation of the vmPFC is involved in processes like self-control and attention-switching:

These findings suggest that the neural mechanisms used in successful self-control can be activated by exogenous attention cues, and provide insights into the processes through which behavioral therapies and public policies could facilitate self-control.

To test the effects of this prefrontal machinery on food choices, a team led by Caltech neuroscientist Antonio Rangel followed up their previous research – which had already confirmed the roles of the vmPFC and dlPFC in valuation and self-control tasks – by showing volunteers photos of food, and asking them to say “yes” or “no” to each one while they lay in an fMRI scanner.

This experiment’s new twist, though, is that after every ten photos, the volunteers were given instructions to “consider the healthiness,” “consider the tastiness,” or to “make decisions naturally.” After the food quiz was over, the scientists then asked the volunteers to rate the same food photos, this time in terms of tastiness and healthiness. These ratings would enable them to correlate the subjects’ food ratings with the fMRI data they’d gathered.

As you might expect, if the food in the photo was both healthy and tasty, the volunteers always tended to rate it highly all ’round. But there were some other cool results, too: thinking about healthiness not only made the subjects less likely to say “yes” to unhealthy foods – it also made them less likely to rate them as “tasty.”

That’s right: thinking of healthiness doesn’t so much shift our attention away from tastiness as it helps us think healthy foods are more tasty!

The next step in the research was to match up the volunteers’ food ratings with their fMRI results:

The vmPFC was, as predicted, more responsive to the healthiness of food in the presence of health cues. And, as the [researchers] had seen previously, the robustness of that response was due to the influence of the dlPFC — that bastion of self-control — which was much quieter when the study’s subjects were thinking about taste or their own personal choice than when they were asked to throw healthiness into the equation.

On a personal note, I’ve definitely found this to be true – I’ve been on a high-protein, low-sugar diet since last year, and (after the first few cranky weeks) I’ve found that I naturally crave meat a lot more than carbs or sugar when I’m hungry – and that I don’t find sugary treats nearly as tasty as I used to. My lust for bacon springs eternal, though.

For the future, the researchers wonder if other unhealthiness signals, like warnings on cigarette labels, might activate the dlPFC in similar ways. I, for one, would be really interested in a study that examined the dlPFC’s role in people’s choices of casual sex partners and long-term mates.

Also, it seems that other cultural influences, like TV commercials and friends’ tastes, would play a big part in determining what we think of as tasty (or otherwise worth partaking in).

Still, leading scientists remain baffled about why anyone thinks this tastes good.

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