University of New South Wales researchers have found yet another side-effect of junk food. Apart from contributing to a bulging waistline, even a short-term junk food consumption could have a significant impact on the brain's cognitive ability.

The finding is based on experiments conducted on lab rats. For the study, the researchers compared performance of rats on a sugar and fat high diet to rodents on a healthy diet.

The researchers found that rats on a diet rich in fat and sugar displayed poor memory after just a week. The rats were unable to detect when an object was displaced to another site. Plus, they had inflammation in the hippocampal region of the brain, which is associated with memory forming and storage. The rats who had highest inflammation suffered from severe memory loss.

"What is so surprising about this research is the speed with which the deterioration of the cognition occurred," research co-author Professor Margaret Morris from UNSW Medicine said in a statement.

Rats, who were exposed to healthy diet and sugar water, also suffered similar consequences.

"It suggests you don't need to be eating high fat to get it, you can be eating high sugar,"  Morris said.Sky News reports. 

The researchers also observed that the memory damage was not reversed when the rats were switched back to healthy diets.

"The animals of course weren't obese after just six days on the diet. So the changes in cognition, the loss of memory, happened well before there was any weight change," Morris said, ABC News Australia reports.

The study also noted that some parts of the memory were out of danger, irrespective of their diets. All the animals were equally able to identify objects after being fed with either the 'healthy,' 'cafeteria' (high in fat and sugar, including cake, chips and biscuits) or 'healthy with sugar' diets.

The finding has been published in the journal Brain, Behaviour and Immunity.