This Is Your Brain on Junk Food
Just about everyone indulges in junk food on occasion. Right? It’s hard not to. It’s so convenient. And fast. And satisfying. Junk food is designed—engineered, really—to appeal to our basest impulses. It’s high in calories—usually from sugar or fat, or both—and low in beneficial nutrients of any kind. Throw in some salt and you have perfectly irresistible food.
Surely an occasional indulgence is okay? Maybe. But new research published in Frontiers in Psychology suggests that, in rats at least, a steady diet of junk food dulls the appetite for new—and healthier—foods. The findings imply that eating lots of junk food alters behavior, weakens self-control, and leads to overeating. And that leads to obesity, of course.
The rats demonstrated a troubling phenomenon. Ordinarily, like other animals, including humans, they have a built-in mechanism that helps them avoid over-eating. Especially a single, specific food. This adaptation ensures that the diet will remain healthy and balanced.
But rats raised on a steady diet of junk food lost this ability to prefer novel foods. After just two weeks on a diet that included cafeteria foods (pie, dumplings, cookies, and cake, with 150% more calories) the rats' weight increased by 10 percent and their behavior changed significantly. They no longer showed interest in new foods when the opportunity to sample them arrived. Researchers think the junk food diet caused lasting changes in parts of the rats' brains containing reward circuitry. The orbitofrontal cortex, for example, is an area of the brain responsible for decision-making.
“The interesting thing about this finding is that if the same thing happens in humans, eating junk food may change our responses to signals associated with food rewards,” said Professor Margaret Morris, of the School of Medical Sciences, in a press release. “It's like you've just had ice cream for lunch, yet you still go and eat more when you hear the ice cream van come by.”
Amy C. Reichelt, Margaret J. Morris, R. F. Westbrook. Cafeteria diet impairs expression of sensory-specific satiety and stimulus-outcome learning. Frontiers in Psychology, 2014; 5 DOI: 10.3389/fpsyg.2014.00852