Could your midlife waistline hint at a future risk for Alzheimer’s disease decades down the road? Scientists from the Washington University School of Medicine in St. Louis, Missouri, sought to answer this very question. Their cutting-edge research, presented at the annual meeting of the Radiological Society of North America (RSNA), delved into the intricate relationship between lifestyle factors – obesity, fat distribution, and metabolism – and the development of Alzheimer’s. What did they uncover? A strong link exists between visceral fat – that stubborn fat deep within the abdomen, surrounding vital organs like the liver, stomach, and intestines – and an increased likelihood of experiencing the first signs of Alzheimer’s nearly two decades later.
Visceral Fat vs. Subcutaneous Fat: A Brain-Specific Threat?
An intriguing study involving 80 individuals, averaging 49 years old and exhibiting normal cognitive function at the time, provided valuable insights. A significant 57.5% of participants were classified as obese, with an average Body Mass Index (BMI) of 32.31. Each participant underwent a thorough evaluation, including full-body MRI scans, metabolic assessments (measuring glucose and insulin levels), and lipid panels (examining cholesterol).
MRI scans focused on the abdomen allowed researchers to meticulously measure both subcutaneous fat (the fat layer beneath the skin) and visceral fat. Brain imaging using Positron Emission Tomography (PET) scans, a powerful technique that generates detailed 3D images, measured early Alzheimer’s biomarkers – the accumulation of tau protein and amyloid plaques in the brain. The higher these levels, the more advanced the disease progression.
“Our study reveals a striking connection between elevated visceral fat and increased PET scan readings of both amyloid and tau – the two pathological proteins hallmarks of Alzheimer’s disease,” explains Dr. Mahsa Dolatshahi, the lead author of the study.
Visceral Fat and Reduced Blood Flow to the Brain
But how does visceral fat contribute to the buildup of tau protein and amyloid plaques in the brain? The answer may lie in its effects on blood flow. Researchers conducted MRI scans of both the brain and abdomen in cognitively normal individuals of average age, spanning a wide range of BMI measurements. By comparing blood flow patterns on the brain MRI, they discovered a significant difference in individuals with higher visceral fat levels: reduced blood flow to the brain. Notably, no such correlation was observed between subcutaneous fat levels and brain blood flow.
Metabolic Factors: Cholesterol’s Protective Role
The study also revealed other significant findings. Higher insulin resistance and lower levels of HDL cholesterol (the “good” cholesterol) were linked to increased amyloid levels in the brain. Conversely, higher levels of “good” cholesterol appeared to lessen the impact of visceral fat on Alzheimer’s development. “A key implication of our research is that managing Alzheimer’s risk in individuals who are obese will likely require addressing the associated metabolic and lipid issues often linked to excess body fat,” states Dr. Cyrus A. Raji, lead author of the study and an associate professor of radiology at the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine.
Targeting Abdominal Fat: A Potential Weapon Against Alzheimer’s? **
“This groundbreaking discovery was possible because we investigated Alzheimer’s pathology in individuals during their 40s and 50s, when the disease is in its nascent stages. Potentially modifiable factors like weight loss and reducing visceral fat are likely to be more effective in preventing or delaying the onset of the disease,” elaborates Dr. Mahsa Dolatshahi.
With nearly 6.9 million Americans aged 65 and older living with Alzheimer’s disease, this number projected to rise to an alarming 13 million by 2050 if effective prevention or curative treatments aren’t developed, efforts to understand and mitigate these risk factors, like visceral fat, become increasingly urgent. Adding another layer to this public health concern, a 2021 study published in The Lancet revealed that in the United States, 208 million people out of a total of 334 million were considered to be overweight or obese.