If you have rats in your house, stop feeding them junk food. It's bad for their health, say scientists. And if you have children in your house, you might want to hear what a diet of too much junk food did to the rats, because there's reason to believe it could be doing the same to them.
The story starts when a pair of researchers got together to see what would happen if they fed rats a regular diet consisting of the same sort of crap we humans consume on a regular basis. What they found is that when rats are fed a diet consisting exclusively of junk food, it alters the brain's reward centers, inducing addictive behavior in rats that is similar to that caused by heroin. “This is the most complete evidence to date that suggests obesity and drug addiction have common neurobiological underpinnings,” reported study coauthor Paul Johnson.
The research was conducted by the Scripps Research Institute in Florida. Scientists separated rats into two groups. One was fed a standard low-calorie, highly nutritious chow. The other group got to gorge themselves on an endless supply of junk food: Ho Ho's, sausage, bacon, cheesecake, and pound cake. Predictably, the junk-food fed rats began to eat compulsively and became obese, taking in twice the calories of the rats in the control group. This revelation wasn't all that surprising, but the next one was notable - and worthy of concern.
They then tested both groups' sensitivity towards feel-good stimulation. After a mere five days on the junk food diet, rats in the test group showed “profound reductions” in sensitivity amongst their brain’s pleasure-reward circuitry. In other words, their pleasure circuitry had become habitualized to the joys of junk food, so that it required a bigger jolt of pleasure to obtain the same feelings of reward when it came to other pleasurable experiences in life. This reduction in sensitivity also meant that the obese rats had to eat more in order to get the same pleasure, just like a drug addict needs more and more of the drug to get the same fix as their body becomes habituated to its effects.
The good news is that this imbalance can be corrected, though not easily. In this study, deficits in the brain's reward circuitry lasted for weeks after the rats stopped eating the junk food. The other area of concern: this was only a rather limited time of exposure. Researchers are worried that when such diets persist not for weeks but for months and years, and especially when this occurs during the sensitive period of childhood, the changes in the brain might be permanent.
It's just another reason why early healthy eating habits are so important. Junk food in itself is not the enemy. It's when parents allow a lack of discretion, and junk food begins to comprise the bulk of a child's normal eating habits, where problems arise. A treat here and there will not ruin your child. In fact, denying children reasonable indulgences is not only mean, it can backfire; leading towards an overcorrection towards overindulgence in adulthood. But too much of a good thing just might habituate your child towards unhealthy habits, dulling their reward centers and setting them down the path towards obesity. Balance is the key.
Try to remember this the next time your child is scarfing down the sugar doughnuts you bought them at the convenience store, which will serve as a snack between the lunch at McDonald's and the take-out pizza planned for dinner. A little junk food here and there won't hurt them, but be sure not to make it a regular habit.