Washington DC [US], November 25 : Scientists discovered that more muscle and less hidden abdominal fat are linked to a younger biological brain age.
Deep visceral fat appeared to accelerate brain ageing, while muscle mass offered a protective effect. Researchers report that people who have more muscle and a lower visceral fat-to-muscle ratio tend to show signs of a younger biological brain age.
This conclusion comes from a study that will be presented next week at the annual meeting of the Radiological Society of North America (RSNA). Visceral fat refers to the fat stored deep in the abdomen around key internal organs.
"Healthier bodies with more muscle mass and less hidden belly fat are more likely to have healthier, youthful brains. Better brain health, in turn, lowers the risk for future brain diseases, such as Alzheimer's." said senior study author Cyrus Raji, M.D., Ph.D., associate professor of radiology and neurology in the Department of Radiology at Mallinckrodt Institute of Radiology at Washington University School of Medicine in St. Louis, Missouri.
How MRI Measures Brain Age and Body Composition
Brain age is an estimate of how old the brain appears biologically, based on its structure as seen through MRI. Body MRI can track muscle mass, which serves as a marker for efforts to reduce frailty and strengthen overall health.
Estimated brain age from structural scans may also shed light on risk factors for Alzheimer's disease, including muscle loss.
"While it is commonly known that chronological ageing translates to loss of muscle mass and increased hidden belly fat, this work shows that these health measures relate to brain ageing itself," Dr Raji said.
"It shows muscle and fat mass quantified in the body are key reflectors of brain health, as tracked with brain ageing," added Dr Raji
Study Details: Imaging, AI Analysis, and Participant Profile
The study evaluated 1,164 healthy adults (52% women) across four research sites using whole-body MRI.
Participants had a mean chronological age of 55.17 years. Imaging included T1-weighted MRI sequences, which highlight fat as bright and fluid as dark, providing a clear view of muscle, fat, and brain tissue.
An artificial intelligence (AI) algorithm measured total normalised muscle volume, visceral fat (hidden belly fat), subcutaneous fat (fat under the skin) and predicted brain age.
The data indicated that individuals with a higher visceral fat to muscle ratio had a higher predicted brain age. Subcutaneous fat showed no meaningful association with how old the brain appeared.
"The participants with more muscle tended to have younger-looking brains, while those with more hidden belly fat relative to their muscle had older-looking brains," Dr Raji said.
"The fat just under the skin wasn't related to brain ageing. In short, more muscle and a lower visceral fat-to-muscle ratio were linked to a younger brain," added Dr Raji.
Implications for Health, Prevention, and Future Interventions
Dr Raji explained that focusing on building muscle and reducing visceral fat are realistic and actionable goals.
Whole-body MRI and AI-based brain age estimates can offer clear benchmarks for programs designed to lower visceral fat while maintaining or increasing muscle.
He also noted that the results highlight the close connection between physical health and brain health.
"This research has validated widely held hypotheses about the association between body composition biomarkers and brain health and provides a foundation for those biomarkers to be included in future trials of various metabolic interventions and treatments," he said.
What the Findings Mean for GLP-1 Weight Loss Drugs
Commonly prescribed glucagon-like peptide-1 (GLP-1) weight loss medications, including Ozempic, are effective at reducing body fat but may also contribute to muscle loss.
Dr Raji suggested that the study's findings could help guide the development of next-generation therapies. These future treatments may aim to reduce visceral fat more than subcutaneous fat while protecting muscle mass.
"Losing fat especially visceral fat while preserving muscle volume would have the best benefit on brain ageing and brain health based on insights from our work," he said.
"Thus, our study can inform future treatments by promoting research that quantifies MRI of body fat, muscle and brain age, which can help determine the optimal dosing regimens for GLP-1s to achieve the best outcomes in body and brain health," added Dr Raji.
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