A new study on rats has found that junk diet prevents animals from seeking novel foods.

Eating balanced diet helps maintain a healthy body. The researchers at the University of New South Wales found that greasy, sweet foods not only make rats fat, but also prevent them from enjoying other kinds of food.

The research shows how junk food diet can alter dietary habits and increase risk of obesity and other health complications.

For the study, the researchers trained young male rats to associate sound cues with particular flavour of sugar water - cherry and grape.

Healthy rats that were on a balanced diet stopped linking the sounds to the flavoured water. This behavior helps animals avoid overeating.

In the next part of the study, the rats were fed junk food. The researchers found that the change in diet altered their behavior. The animals became uninterested in seeking novel foods and became indifferent to tastes.

The researchers believe that junk food might later brain circuitry, especially in a region called orbitofrontal cortex, which is associated with decision making abilities of the animal. the team says that the findings might apply to humans as all mammals share the same reward circuitry in the brain.

"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 Margaret Morris, Head of Pharmacology from the School of Medical Sciences, UNSW Australia, according to a news 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."

The study suggests that overweight or obese people might find it hard to resist junk diet because their brains are hard-wired to like a specific group of foods.

"As the global obesity epidemic intensifies, advertisements may have a greater effect on people who are overweight and make snacks like chocolate bars harder to resist," added Dr Amy Reichelt, lead author of the paper and UNSW postdoctoral associate.

The study is published in the journal Frontiers in Psychology.

Related research has shown that junk food can negatively affect sense of smell in mice.