Junk Food Diet Keeps Rats from Seeking Out New Foods

It’s no secret that calorie-rich foods are a major contributor to weight gain and obesity. But a junk food diet doesn’t just pack on the pounds, it may reduce a person’s desire to eat a more diverse diet. Brains are wired to not overeat too much of one thing and to seek out different foods.
However, a new study has found that rats on a junk food diet appear to lose the desire for other kinds of food. In a recent study published in Frontiers in Psychology, researchers from Australia showed that rats eating a diet of high-calorie foods like cookies, pie, dumplings, and cake for two weeks not only gained weight but also lost their desire to seek out different foods. A diet of diverse foods is typically a healthier diet because it means that you’re not eating too much of any one item.
Researchers conditioned young male rats to associate different sound cues with either cherry- or grape-flavored sugar water. Healthy rats eventually stopped responding to cues for flavors that they had recently overindulged in. This natural mechanism limits overeating. But when researchers put rats on an unhealthy diet of high-fat foods for two weeks with 150 percent more calories than the healthy diet, the rats became indifferent to diverse foods and would continue to eat the flavored water they had recently indulged in. Even after being put on a healthy diet, these junk food rats didn’t appear to seek out new flavors.