Excessive fat has been linked to numerous health conditions, even some that affect the brain.

In the most recent Alzheimer’s research, hidden fat in specific parts of the body was shown to be an early warning sign of the most common dementia — as much as 20 years before the emergence of the symptoms.

Study findings were presented this week at the annual Radiological Society of North America (RSNA) meeting in Chicago.

“Among different body compartments, higher visceral or hidden belly fat is the most important predictor of whole-brain amyloid and early tau protein accumulation,” said Mahsa Dolatshahi, M.D., lead study author and post-doctoral research associate at Mallinckrodt Institute of Radiology (MIR) at the Washington School of Medicine.

Researchers studied different body tissues— liver fat, thigh fat, and subcutaneous fat. However, visceral fat was the “most powerful predictor of the obesity-related Alzheimer’s disease (AD) pathologies,” noted Dolatshahi. “The other types of fat did not show any associations with AD pathologies.”

According to the press release, researchers assessed 80 middle-aged adults (an average of 49 years old) who didn’t have any cognitive impairment.

Only half of the individuals were categorized as obese.

Average body mass index (BMI) was 32.31, with anything over 30 falling into the obesity category.

Researchers assessed the possible connection between signs of Alzheimer’s disease and lifestyle factors that are controllable, including BMI, obesity, and metabolic health.

Tests included body MRIs, brain scans, blood glucose and insulin level measurements, and cholesterol panels.

The release noted that the study went beyond measuring BMI and utilized MRI technology to examine body fat more closely and better determine its relationship to Alzheimer’s.

“We investigated the association of BMI, visceral fat, subcutaneous fat, liver fat fraction, thigh fat and muscle, as well as insulin resistance and HDL (good cholesterol), with amyloid and tau deposition in Alzheimer’s disease,” Dolatshahi said.

Another finding was that higher insulin resistance and lower HDL were associated with high amyloid in the brain — a hallmark of Alzheimer’s.

“A key implication of our work is that managing Alzheimer’s risk in obesity will need to involve targeting the related metabolic and lipid issues that often arise with higher body fat,” said Cyrus A. Raji, M.D., Ph.D., senior author of the study and associate professor of radiology at MIR, in the release.

In a separate study also presented this week, the same research team investigated how belly fat and obesity can impair blood flow to the brain.

Three out of four Americans are obese or overweight, researchers noted.

In the meantime, approximately 6.9 million Americans, ages 65 and older, have been diagnosed with Alzheimer’s disease — a number predicted to reach 13 million by 2050.

Dr. Earnest Lee Murray, a board-certified neurologist at Jackson-Madison County General Hospital in Jackson, Tennessee, wasn’t involved in the study but commented on its results.

“We have known for some time the dangers of visceral fat on various organs of the body, likely from its facilitation of inflammatory changes — and it’s no different in the brain,” said Murray.

What stuck out the most to Murray was how early in life the changes are noticed in the brain.

“The good news is these risk factors can be lowered with a healthy lifestyle and routine exercise,” said Murray.

Murray added that the popularity of GLP-1 medications for obesity and diabetes “will most certainly be studied” in this context as well.

“This study also shows the importance of physicians and insurance companies focusing on prevention and the long-term benefits of modifying risk factors at an early age, as opposed to waiting for patients to develop symptoms,” said Murray.

Researchers acknowledged the study did have some limitations.

“One is the cross-sectional design of the study, which does not allow us to understand whether the individuals with excess visceral fat and amyloid and tau pathologies will develop cognitive impairment and symptomatic AD,” said Dolatshahi.

“Also, the sample size for this study is limited to 80 individuals, and we need more studies to understand the role of different kinds of body adiposity in Alzheimer’s disease using PET scans.”