Hidden belly fat ages the brain - but muscle keeps it young

Science keeps uncovering new links between how we live and how our brains age. Many people still picture the brain as something isolated, protected from the rest of the body.

Yet research continues to show that our physical traits shape the inner workings of the mind more than we expect.

A new study strengthens that idea with clear imaging evidence. The results suggest that muscle and hidden fat may play quiet but powerful roles in keeping the brain youthful.

Not all fats are the same

The study centers on a simple pattern. People with more muscle and less hidden belly fat show a younger brain age on MRI scans.

Hidden fat sits near vital organs and influences metabolism in strong ways. It can drive inflammation and raise health risks.

Fat under the skin behaves differently and does not show the same harmful pattern. The work highlights that not all fat acts the same.

More muscle, healthier brain

The researchers looked at these traits in healthy adults. They used whole body MRI to capture detailed images of muscle, fat, and brain tissue.

The results produced a clear and repeatable link between body shape and brain aging.

This connection adds to a growing field that studies how metabolic health influences cognition. It also shows why strength and body composition matter far beyond appearance.

Dr. Cyrus Raji from the Washington University School of Medicine is the study’s senior author.

“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 Dr. Raji.

Key reflectors of brain health

Brain age shows how old the brain appears when compared with large imaging datasets. A younger estimate can signal healthier neural structure.

Many teams now use brain age in studies on aging, memory decline, and disease risk. This tool helps researchers track subtle changes that normal tests may miss.

“While it is commonly known that chronological aging translates to loss of muscle mass and increased hidden belly fat, this work shows that these health measures relate to brain aging itself,” Dr. Raji said.

“It shows muscle and fat mass quantified in the body are key reflectors of brain health, as tracked with brain aging.” 

Imaging the entire body

The study enrolled more than 1,000 adults across four research sites. Their average age was in the mid-fifties, but brain age varied widely.

Whole-body MRI measured each participant’s muscle volume, visceral fat, and subcutaneous fat. T1-weighted images provided crisp separation of these tissues. An AI model then analyzed the scans to estimate each person’s brain age.

The AI system measured patterns across the entire scan rather than focusing on one region. This broad approach revealed how body composition links with brain structure.

People with more muscle tended to show younger appearing brains. People with more hidden fat relative to muscle tended to show older appearing brains.

“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 aging.” 

Muscle and brain changes matter

These findings matter because people can change these traits. Muscle grows with strength training. Hidden fat drops with targeted lifestyle changes.

These shifts can happen across adulthood, making them practical goals. MRI and AI tools offer precise ways to track these changes in future trials. They turn muscle and fat measures into clear markers for brain health.

“This research has validated widely held hypotheses about the association between body composition biomarkers and brain health,” Dr. Raji said. 

The researchers also noted that these markers can support studies on metabolic therapies.

Experts can design programs that cut hidden fat without harming muscle. Over time, this could guide strategies for preventing cognitive decline.

Future treatment clues

The study also has implications for future weight-loss drugs. GLP-1 medications remain hugely popular, but they can strip away muscle along with fat – a combination that may affect long-term brain health.

The new findings suggest that the ideal therapy would target hidden visceral fat while preserving muscle.

“Losing fat, especially visceral fat, while preserving muscle volume would have the best benefit on brain aging and brain health, based on insights from our work,” Dr. Raji said. 

This idea may shape next generation treatments. New drugs could target harmful fat more precisely. AI-based imaging could help doctors monitor how the body responds.

These tools open doors for more personalized care where body shape becomes an early signal of brain risk.

The research is published by the Radiological Society of North America (RSNA).

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