In the small pilot study, 13 obese and overweight participants were assigned to a control or intervention group. Those in the intervention group took part in a version of the I Diet, which involved portion control, an emphasis on low-glycemic foods, and 19 support meetings delivered over 24 weeks. Participants in this group also received individualized emails from their nutritionists for support. Control participants eventually got the I Diet intervention as well, but were waitlisted for six months while this study took place.
All participants also got a functional magnetic resonance imaging (fMRI) scan before and after the six months were up. While in the machine, they were shown 40 food and 40 non-food control-image cues. The food cues, such as sandwiches and french fries, included both high- and low-calorie options. The non-food cues were images that sorta-kinda looked similar to the food cues — but were definitely not food (e.g. a wallet, or pencils).
The researchers focused their scans on each participant's striatum, an area that's often associated with the brain's dopamine-rich reward processes. They found significantly higher average amounts of activation in this area for the low-calorie food images than high-calorie foods, but only in participants who had already been through the I Diet program. The control participants showed the opposite: more activation in the striatum for high-calorie foods. This suggests that changing what we eat eventually changes what we crave.
However, like all fMRI results, these are indirect measurements of neural activity; they're based on secondary factors (such as changes in blood oxygen levels) rather than on actual imagery of the brain area and its activation level. And, yeah, 13 people is a pretty tiny number to make big, sweeping statements about. So, while these results certainly make sense — and anecdotal evidence shows we can think of carrots as dessert if we stop eating sugar for long enough — this study doesn't provide firm proof of that. It is, however, the first evidence that behavioral intervention can change brain activation to favor healthy over unhealthy food. Which somehow seems less laughable than those ridiculous brain training games.