We all know how difficult it is to say no to junk food. Fries, chips, cakes, cookies, burgers, pizza (drool) all stare at us in the supermarket, making the salad bar look infinitely less appealing. But being delicious is not the only reason that we want to eat junk food.
Overindulging in unhealthy food for a prolonged period of time can cause excessive activation of the brain’s reward system for high-calorie food cues, which makes us more likely to choose that oozy chocolate pudding over an apple when a selection is available. However, all may not be lost for us. A new pilot study, published in Nutrition & Diabetes, suggests that it may be possible to gradually train the brain to prefer healthy foods over junk foods, reversing the addictive power of unhealthy food.
It’s been known for some time that obesity is associated with abnormalities in the reward circuit of the brain. Whether this is plastic and can therefore be reversed, however, was unknown. To shed light on this area, Tufts University researchers enrolled 13 healthy, adult, overweight or obese men and women into the study. Eight of the participants took part in a specific weight loss program designed by the researchers, whereas the remaining five acted as controls and were placed on a waiting list for the program.
The intervention group was given portion-controlled menus, recipe suggestions and high-satiety menu plans. The recipes had specific compositions designed to reduce hunger, such as providing 25% energy from protein and fat and 50% from low GI carbs. They were also given information on snack selection and evenly spacing meals.
To investigate whether the program could alter neural circuitry, the researchers took functional magnetic resonance imaging (fMRI) scans before the participants were randomized into groups, and did this again six months later. The scans were used to investigate activity in a brain region called the striatum which is thought to be critical for reward processing.
When the participants were presented with images of healthy, low-calorie foods, they found that those in the diet group showed significantly more activity in their reward centers compared to the control group. Reward center activation also significantly decreased in the diet group when images of unhealthy, high-calorie foods were shown. According to the researchers, this suggests the participants experienced an increased reward and enjoyment of healthy food.
“The weight loss program is specifically designed to change how people react to different foods, and our study shows those who participated in it had an increased desire for healthier foods along with a decreased preference for unhealthy foods, the combined effects of which are probably critical for sustainable weight control,” study author Sai Krupa Das said in a news release. “To the best of our knowledge, this is the first demonstration of this important switch.”
I’m sure many have already noticed that this study is very small, therefore it is difficult to be confident about the results. Furthermore, baseline dietary restraint was different between the two groups of participants, which they acknowledge could have affected the outcome. However, larger studies in the future would address these issues and hopefully make the results more watertight.