WASHINGTON: Just a few days of eating a diet high in saturated fat could be enough to cause memory problems and related brain inflammation in older adults, a new study in rats suggests.
Researchers fed separate groups of young and old rats the high-fat diet for three days or for three months to compare how quickly changes happen in the brain versus the rest of the body when eating an unhealthy diet.
As expected based on previous diabetes and obesity research, eating fatty foods for three months led to metabolic problems, gut inflammation and dramatic shifts in gut bacteria in all rats compared to those that ate 'normal chow', while just three days of high fat caused no major metabolic or gut changes.
Notably, 'Normal chow' is a term used to describe a standard diet for laboratory animals that is made from grains, cereals, and animal by-products.
When it came to changes in the brain, however, researchers found that only older rats -- whether they were on the high-fat diet for three months or only three days -- performed poorly on memory tests and showed negative inflammatory changes in the brain.
The results dispel the idea that diet-related inflammation in the aging brain is driven by obesity, said senior study author Ruth Barrientos, an investigator in the Institute for Behavioral Medicine Research at The Ohio State University. Most research on the effects of fatty and processed foods on the brain has focused on obesity, yet the impact of unhealthy eating, independent of obesity, remains largely unexplored.
"Unhealthy diets and obesity are linked, but they are not inseparable. We're really looking for the effects of the diet directly on the brain. And we showed that within three days, long before obesity sets in, tremendous neuroinflammatory shifts are occurring," said Barrientos, also an associate professor of psychiatry and behavioral health and neuroscience in Ohio State's College of Medicine.
"Changes in the body in all animals are happening more slowly and aren't actually necessary to cause the memory impairments and changes in the brain. We never would have known that brain inflammation is the primary cause of high-fat diet-induced memory impairments without comparing the two timelines."
The research was published recently in the journal Immunity & Ageing.