Summary: A new research shows that only three days of a high-fat eating can cause memory impairments and mental disease in older adults, separate of overweight. Scientists compared young and old rats fed a diet with 60 % of calories from fat and found that only the older rats showed mental decline.
While biochemical and colon health changes took months to seem, memory deficits emerged rapidly in the younger brains. The findings suggest that diet-related mental disease is not only driven by obesity but occurs fast with bad eating.
Important Information:
- Only three days of a high-fat eating caused memory deficits in older animals.
- Mental disease occurred before biochemical and gut health adjustments.
- Fresh animals on the same eating did not experience mental decline.
Origin: Ohio State University
 , Just a few weeks of eating a diet high in saturated fats could be enough to cause memory problems and associated mental disease in older people, a new study in animals suggests.
Researchers fed distinct groups of young and aged rats the high-fat meal for three days or for three months to evaluate how fast changes happen in the mind versus the rest of the brain 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.
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.
Years of research in Barrientos ‘ lab has suggested that aging brings on long-term “priming” of the brain’s inflammatory profile coupled with a loss of brain-cell reserve to bounce back, and that an unhealthy diet can make matters worse for the brain in older adults.
Fat constitutes 60 % of calories in the high-fat diet used in the study, which could equate to a range of common fast-food options: For example, nutrition data shows that fat makes up about 60 % of calories in a McDonald ‘s , double smoky BLT quarter pounder with cheese , or a Burger King , double whopper with cheese.
After the animals were on high-fat diets for three days or three months, researchers ran tests assessing two types of memory problems common in older people with dementia that are based in separate regions of the brain: contextual memory mediated by the , hippocampus , ( the primary memory center of the brain ), and cued-fear memory that originates in the , amygdala , ( the fear and danger center of the brain ).
Compared to control animals eating chow and young rats on the high-fat diet, aged rats showed behaviors indicating both types of memory were impaired after only three days of fatty food – and the behaviors persisted as they continued on the high-fat diet for three months.
Researchers also saw changes in levels of a range of proteins called cytokines in the brains of aged rats after three days of fatty food, which signaled a dysregulated inflammatory response. Three months after being on the high-fat diet, some of the cytokine levels had shifted but remained dysregulated, and the cognitive problems persisted in behavior tests.
” A departure from baseline inflammatory markers is a negative response and has been shown to impair learning and memory functions”, Barrientos said.
Compared to rats eating normal chow, young and old animals gained more weight and showed signs of metabolic dysfunction – poor insulin and blood sugar control, inflammatory proteins in fat (adipose ) tissue, and gut microbiome alterations– after three months on the high-fat diet. Young rats ‘ memory and behavior and brain tissue remained unaffected by the fatty food.
” These diets lead to obesity-related changes in both young and old animals, yet young animals appear more resilient to the high-fat diet’s effects on memory. We think it is likely due to their ability to activate compensatory anti-inflammatory responses, which the aged animals lack”, Barrientos said.
” Also, with glucose, insulin and adipose inflammation all increased in both young and old animals, there’s no way to distinguish what is causing memory impairment in only old animals if you look only at what’s happening in the body. It’s what is happening in the brain that’s important for the memory response”.
Funding: This work was supported by grants from the , National Institute on Aging.
Co-authors include Michael Butler, Stephanie Muscat, Brigitte González Olmo, Sabrina Mackey-Alfonso, Nashali Massa, Bryan Alvarez, Jade Blackwell, Menaz Bettes and James DeMarsh of Ohio State, and Maria Elisa Caetano-Silva, Akriti Shrestha, Robert McCusker and Jacob Allen of the University of Illinois at Urbana-Champaign.
About this diet and memory research news
Author: Emily Caldwell
Source: Ohio State University
Contact: Emily Caldwell – Ohio State University
Image: The image is credited to Neuroscience News
Original Research: Open access.
” Obesity-associated memory impairment and neuroinflammation precede widespread peripheral perturbations in aged rats” by Ruth Barrientos et al. Immunity &, Aging
Abstract
Obesity-associated memory impairment and neuroinflammation precede widespread peripheral perturbations in aged rats
Background
Obesity and metabolic syndrome are major public health concerns linked to cognitive decline with aging. Prior work from our lab has demonstrated that short-term high fat diet ( HFD ) rapidly impairs memory function via a neuroinflammatory mechanism. However, the degree to which these rapid inflammatory changes are unique to the brain is unknown.
Moreover, deviations in gut microbiome composition have been associated with obesity and cognitive impairment, but how diet and aging interact to impact the gut microbiome, or how rapidly these changes occur, is less clear.
Thus, our study investigated the impact of HFD after two distinct consumption durations: 3 , months ( to model diet-induced obesity ) or 3 , days ( to detect the rapid changes occurring with HFD ) on memory function, anxiety-like behavior, central and peripheral inflammation, and gut microbiome profile in young and aged rats.
Results
Our data indicated that both short-term and long-term HFD consumption impaired memory function and increased anxiety-like behavior in aged, but not young adult, rats. These behavioral changes were accompanied by pro- and anti-inflammatory cytokine dysregulation in the hippocampus and amygdala of aged HFD-fed rats at both time points.
However, changes to fasting glucose, insulin, and inflammation in peripheral tissues such as the distal colon and visceral adipose tissue were increased in young and aged rats only after long-term, but not short-term, HFD consumption.
Furthermore, while subtle HFD-induced changes to the gut microbiome did occur rapidly, robust age-specific effects were only present following long-term HFD consumption.
Conclusions
Overall, these data suggest that HFD-evoked neuroinflammation, memory impairment, and anxiety-like behavior in aging develop quicker than, and separately from the peripheral hallmarks of diet-induced obesity.
