Brain counts calories, or maybe not? | Day 67

Instead of talking about wonderful or fascinating science, today it’s time for something I think is pretty lousy.

A team of scientists in Canada decided to see whether people are willing to pay more for high calorie foods when presented with a simulated auction-type scenario. In the paper, published in Psychology Science, they describe their intent thus: “Understanding the attributes of foods that predict value, and the influence of learned attributes of food, may provide information on how food choices are made in an increasingly obesogenic food environment.”

To dress the study up, they strapped people into fMRI machines to look at some brain scans for good measure, while determining their willingness to pay for food items depicted.

Here’s the method in a nutshell: 29 healthy people were asked to look at pictures of 50 familiar foods, both low-calorie, such as fruit and veg, and high-calorie, such as sweet and savoury junk foods. I think it’s safe to assume these were the food categories included, but the paper doesn’t provide a list of food items. Oh, well.

So, these people were asked to rate how much they liked each food on a scale from 1-20, and estimate the caloric content of said food item. The results showed that in general their estimates were not very good.

On a separate day, the same participants were asked to come back and this time bid, while getting a brain scan, on the foods they would want to eat. Apparently, the amount participants were willing to pay correlated with the foods that had a higher caloric density. It didn’t, however, correlate with what foods they liked.

Are you confused yet?

Here’s a quote about the results of the brain scan part of the study:

Results of functional brain scans acquired while participants looked at the food images showed that activity in the ventromedial prefrontal cortex, an area known to encode the value of stimuli and predict immediate consumption, was also correlated with the foods’ true caloric content.

In other words, people gravitated towards foods with a higher caloric content, even though they didn’t know this caloric content precisely.

The researchers used this as evidence to claim that “an internal calorie counter of sorts is also evaluating each food based on its caloric density.”

However, what keeps us from concluding that people are willing to pay more for a chocolate than, say, a kale leaf? Regardless of whether they even like kale, or chocolate, or being strapped into an fMRI machine while feeling increasingly hungry?

I conclude that the study design is so baffling it’s hard to conclude anything. Or did I miss something? Oh great, now I’m hungry, too.

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