The study, which has been published in the journal Brain, Behavior and Immunity, saw researchers at the University of New South Wales finding that rats fed a diet high in fat and sugar had impaired memory after just a week.
The researchers also found that the results were similarly poor for the rats fed a healthy diet but given access to sugar water to drink.
According to the study, the cognitive impairment was related to place recognition, with the animals showing poorer ability to notice when an object had been shifted to a new location. These animals also had inflammation of the hippocampal region of the brain, which is associated with spatial memory, it said.
“We know that obesity causes inflammation in the body, but we didn’t realise until recently that it also causes changes in the brain,” said Margaret Morris, study author and professor at the UNSW School of Medical Sciences.
“What is so surprising about this research is the speed with which the deterioration of the cognition occurred,” said Morris. “Our preliminary data also suggests that the damage is not reversed when the rats are switched back to a healthy diet, which is very concerning.”
According to the study, some aspects of the animals’ memories were spared, regardless of their diets. All animals were equally able to recognise objects after eating either the “healthy”, “cafeteria” (high in fat and sugar, including cake, chips and biscuits) or “healthy with sugar” regimes.
Without a cue
Researchers said that the change in the animals’ memory appeared even prior to the emergence of weight differences between the animals and that work will be done to establish how to stop the inflammation in the brain of animals with the unhealthy diets.
“We suspect that these findings may be relevant to people,” said Morris. “While nutrition affects the brain at every age, it is critical as we get older and may be important in preventing cognitive decline. An elderly person with poor diet may be more likely to have problems. ”
“Given that high energy foods can impair the function of the hippocampus, if you eat a lot of them it may contribute to weight gain, by interfering with your episodic memory,” she said. “People might be less aware of their internal cues like hunger pangs and knowing when they have had enough,” she said.
This work by was funded by the National Health and Medical Research Council.
Brain, Behavior and Immunity
Jessica Beilharz, Jayanthi Maniam and Margaret Morris