Rats whose diet consists primarily of junk food become fat and lose their appetite for a balanced diet, a new study shows. The fast food diet decreases the desire among rats to eat a balanced diet, according to the study, which was published in the open-access journal Frontiers in Psychology.

The study helps to explain the result of consuming excessive amounts of junk food, which may alter behavior, weaken an individual’s self-control, and promote overeating and obesity.

The team of researchers, which was led by Professor Margaret Morris, Head of Pharmacology from the School of Medical Sciences, UNSW Australia, taught young male rates to associate cherry and grape-flavored sugar water with two different sound cues.

Healthy rats that consumed a healthy diet stopped responding to the sound cues that were linked to a flavor which they had recently overindulged in. This instinctive mechanism, which is widespread among animals, offers protection against overeating while promoting a healthy and balanced diet.

After two weeks following a diet that included cafeteria food such as pie, cake, dumplings, and cookies, the rats experienced a 10 percent weight increase along with a drastic change in behavior, including indifference in food choices.

Morris said in a statement, “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.” She continued, “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.”

According to the Centers for Disease Control and Prevention, over one third, or 78.6 million, of adults in the U.S. are obese.

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