Sydney, Aug 28 (IANS): A fast food diet can not only make you obese but also reduces your appetite for normal, balanced diets.

According to Australian researchers, excessive consumption of junk food can change behaviour, weaken self-control and lead to over-eating.

In lab experiments, they found that a diet of junk food reduced rats' appetite for novel foods, a preference that normally drives them to seek a balanced diet.

"If the same thing happens in humans, eating junk food may change our responses to signals associated with food rewards," said professor Margaret Morris from University of New South Wales Australia.

During the study, the team taught young male rats to associate sound cues with different flavours of sugar water -- cherry and grape.

But after two weeks on a diet that included pies, dumplings, cookies and cakes, the rats' weight increased by 10 percent and their behaviour changed dramatically.

They became indifferent towards their food choices and no longer avoided the sound advertising the over-familiar taste.

"This indicated that they had lost their natural preference for novelty. The change even lasted for some time after the rats returned to a healthy diet," Morris added.

The study was published in the journal Frontiers in Psychology.