Visceral fat, the type of fat stored deep in the abdomen, may signal an increased risk of Alzheimer's disease up to 20 years before symptoms emerge, according to research presented at the Radiological Society of North America's (RSNA) annual meeting. The findings shed new light on the connection between obesity and brain health, offering insights that could shape prevention strategies for the most common form of dementia.
"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 Dr. Mahsa Dolatshahi, lead author of the study and post-doctoral research associate at the Mallinckrodt Institute of Radiology at Washington University School of Medicine. Amyloid plaques and tau tangles are hallmark pathologies of Alzheimer's disease, often appearing years before cognitive decline.
Researchers studied 80 middle-aged participants, averaging 49 years old, with no signs of cognitive impairment. Using MRI scans, blood tests, and PET imaging, the team examined the relationship between different types of body fat and the development of Alzheimer's-associated proteins. "Visceral fat was the most powerful predictor of obesity-related Alzheimer's pathologies," Dolatshahi noted. Other types of fat, such as subcutaneous and liver fat, showed no significant connection.
The findings highlight the role of metabolic health in Alzheimer's risk. Participants with higher insulin resistance and lower levels of high-density lipoprotein (HDL), or "good cholesterol," were found to have elevated levels of amyloid plaques in their brains. "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 senior study author Dr. Cyrus A. Raji, associate professor of radiology at the Mallinckrodt Institute of Radiology.
Visceral fat is stored deep within the abdominal cavity, surrounding vital organs like the stomach, liver, and intestines. It is linked to inflammation and chronic diseases, including diabetes and cardiovascular problems, according to the Cleveland Clinic. "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 Dr. Earnest Lee Murray, a neurologist at Jackson-Madison County General Hospital, who was not involved in the study.
The implications of these findings are significant. Nearly three-quarters of Americans are overweight or obese, according to the researchers, and approximately 6.9 million Americans aged 65 and older currently live with Alzheimer's. That number is projected to more than double by 2050. "Knowing that visceral obesity negatively affects the brain opens up the possibility that treatment with lifestyle modifications or appropriate weight-loss drugs could improve cerebral blood flow and potentially lower the burden of Alzheimer's disease," Raji said.
Lifestyle changes could play a pivotal role in prevention. Regular physical activity, a balanced diet, and managing conditions like diabetes and high blood pressure are all effective strategies for reducing dementia risk, according to the Centers for Disease Control and Prevention. "The good news is these risk factors can be lowered with a healthy lifestyle and routine exercise," Murray added.
The study, however, comes with limitations. It involved a relatively small sample size of 80 participants, and its cross-sectional design means it could not establish whether individuals with excess visceral fat and Alzheimer's pathologies will go on to develop symptoms. "We need more studies to understand the role of different kinds of body adiposity in Alzheimer's disease using PET scans," Dolatshahi said.
The researchers also explored how obesity impairs blood flow to the brain, a factor linked to cognitive decline. The popularity of weight-loss drugs such as GLP-1 medications presents a potential avenue for further research. "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," Murray noted.
