Researchers in Germany have discovered that a hidden type of fat deep inside muscles may reveal serious health risks long before symptoms appear.
Using MRI scans and artificial intelligence, scientists found strong links between hidden muscle fat and conditions such as high blood pressure, unhealthy cholesterol levels, and abnormal blood sugar.
The study was published in the medical journal Radiology and involved more than 11,000 adults who had no known major diseases at the time of testing.
Doctors have traditionally focused on body weight and visible fat when assessing health risks. However, scientists are increasingly learning that where fat is stored inside the body may matter just as much as how much fat a person carries overall.
One important type is intermuscular fat. This fat builds up between muscle fibers and around muscles deep inside the body. Unlike belly fat or fat under the skin, intermuscular fat cannot usually be seen without imaging tests such as MRI scans.
Researchers now believe this hidden fat may quietly affect metabolism, blood vessels, inflammation, and heart health.
The study was led by Dr. Sebastian Ziegelmayer at the Technical University of Munich. The research team wanted to explore whether muscle composition could reveal hidden cardiometabolic risk.
Cardiometabolic conditions include diseases involving the heart, circulation, blood sugar, metabolism, and cholesterol. These include hypertension, diabetes, obesity, and cardiovascular disease.
Scientists already know that muscles are not simply tissues used for movement and strength. Muscles also play a major role in controlling blood sugar, processing energy, and regulating inflammation throughout the body.
To better understand these relationships, the researchers studied whole-body MRI scans from 11,348 adults examined at five imaging centers. The participants had no previously diagnosed major illnesses, making the study especially interesting because researchers could identify hidden risks in people who appeared healthy.
The average participant was 43 years old, and about 57% were men.
The researchers focused on the paraspinal muscles, which run alongside the spine from the neck to the pelvis. These muscles help stabilize the body and support posture.
Using a deep learning computer model, the researchers automatically analyzed the MRI scans. Deep learning is a type of artificial intelligence designed to recognize patterns and make predictions from large amounts of information.
The computer system measured both lean muscle tissue and intermuscular fat. This type of analysis previously required specialists to spend many hours reviewing images manually, but artificial intelligence made it possible to analyze thousands of scans efficiently.
The scientists then compared the imaging results with health data collected from participants, including blood pressure, blood sugar levels, cholesterol levels, and exercise habits.
The findings showed that hidden health risks were surprisingly common.
More than 16% of participants had previously undiagnosed hypertension. About 8.5% had abnormal blood sugar levels, and almost 46% had unhealthy lipid profiles. Lipids are fatty substances in the blood, including cholesterol and triglycerides.
Researchers found that participants with higher amounts of hidden muscle fat were much more likely to have these unhealthy cardiometabolic conditions.
Even after adjusting for age, sex, physical activity, and study location, the relationship remained strong.
The study also found that lean muscle tissue may offer protection against disease risk, especially in men. Men with more healthy muscle mass generally showed lower cardiometabolic risk.
The findings in women were more complex. Researchers observed that women’s lean muscle mass stayed relatively stable until around age 40 to 50 before declining significantly. The researchers believe menopause and falling estrogen levels may partly explain why the protective effect appeared weaker in women.
Physical activity also played an important role. People who exercised less tended to have more hidden fat and lower lean muscle mass. This supports earlier research showing that regular exercise may improve muscle quality and metabolic health.
The researchers believe MRI scans could eventually become useful tools for early disease screening. Because MRIs are already performed for many medical reasons, doctors may one day be able to gather additional health information from scans patients are already receiving.
For example, an MRI ordered for spine problems could potentially reveal hidden risks for heart disease or diabetes at the same time.
Researchers say this could allow doctors to identify high-risk individuals much earlier, even when standard medical tests appear normal.
The study also demonstrates the growing role of artificial intelligence in modern medicine. AI systems are increasingly being used to analyze scans, predict disease risk, and assist doctors in making earlier diagnoses.
Still, the researchers caution that more work is needed before this technology becomes routine in hospitals. The current study was observational, meaning it found links between muscle fat and disease risk but did not prove direct cause and effect.
However, the very large number of participants and the consistency of the findings suggest the results are highly important.
Overall, the study suggests that muscle composition may reveal much more about a person’s health than previously understood. Hidden fat inside muscles could become a powerful warning sign for future cardiovascular and metabolic disease.
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The research findings were published in the journal Radiology.
Source: Technical University of Munich.
