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• Posted November 20, 2023

Fat Hiding Around Organs Could Raise Odds for Alzheimer's

Middle-aged folks with lots of belly fat surrounding their internal organs appear to be at higher risk for Alzheimer's disease later in life, a new study suggests.

This hidden abdominal fat -- known as visceral fat -- is related to changes in the brain up to 15 years before the earliest symptoms of Alzheimer's manifest, according to findings to be presented at next week's annual meeting of the Radiological Society of North America. Such research is considered preliminary until published in a peer-reviewed journal.

For this study, researchers compared brain scans of 54 people between the ages of 40 and 60 with their levels of belly fat, BMI, obesity and insulin resistance.

The scans looked for the size of people's brains, as well as levels of amyloid beta and tau proteins that have been previously linked to Alzheimer's.

"Even though there have been other studies linking BMI with brain atrophy or even a higher dementia risk, no prior study has linked a specific type of fat to the actual Alzheimer's disease protein in cognitively normal people,"said researcher Dr. Mahsa Dolatshahi, a postdoctoral research fellow with the Mallinckrodt Institute of Radiology at Washington University School of Medicine in St. Louis.

"Similar studies have not investigated the differential role of visceral and subcutaneous fat, especially in terms of Alzheimer's amyloid pathology, as early as midlife,"Dolatshahi noted in a meeting news release.

Researchers found that people who had more visceral fat compared with fat found just under their skin tended to have higher amyloid levels in the precuneus cortex, the region known to be affected early by amyloid pathology in Alzheimer's disease.

This relationship was worse in men than in women, and higher visceral fat measurements also were related to increased inflammation in the brain, researchers said.

"Several pathways are suggested to play a role,"Dolatshahi said. "Inflammatory secretions of visceral fat -- as opposed to potentially protective effects of subcutaneous fat -- may lead to inflammation in the brain, one of the main mechanisms contributing to Alzheimer's disease."

These findings could help doctors diagnose and treat people at risk for Alzheimer's, said senior researcher Dr. Cyrus Raji, director of neuromagnetic resonance imaging with the Mallinckrodt Institute of Radiology.

"This study highlights a key mechanism by which hidden fat can increase the risk of Alzheimer's disease,"Raji said. "It shows that such brain changes occur as early as age 50, on average -- up to 15 years before the earliest memory loss symptoms of Alzheimer's occur."

By reducing a person's amount of visceral fat, doctors might be able to reduce future brain inflammation and head off dementia or Alzheimer's, Raji said.

"By moving beyond body mass index in better characterizing the anatomical distribution of body fat on MRI, we now have a uniquely better understanding of why this factor may increase risk for Alzheimer's disease,"Raji said.

More information

Harvard Medical School has more on visceral fat.

SOURCE: Radiological Society of North America, news release, Nov. 20, 2023