Researchers Identify Hidden Muscle Fat as a New Risk Factor for Heart Disease and Metabolic Disorders

Researchers analyzing more than 11,000 adults in a 2026 multicenter study found that higher amounts of hidden fat inside muscles were linked to increased risk factors for heart disease and metabolic disorders. According to the study, published this year, this intermuscular fat was associated with high blood pressure, unstable blood sugar, and unhealthy cholesterol levels independent of traditional body size measures.

The study, published in 2026, analyzed more than 11,000 adults without known pre-existing conditions, drawn from a prospective, multicenter population cohort. Researchers used whole-body MRI scans combined with a deep learning algorithm to measure lean muscle mass and intermuscular adipose tissue—fat hidden within muscles along the spine. According to Dr. Ziegelmayer, a lead investigator on the project, the analysis revealed that higher amounts of this hidden muscle fat were linked to increased odds of hypertension, unstable blood sugar, and unhealthy cholesterol levels, independent of traditional body size measures such as body mass index.

The findings showed that 16.2% of participants had undiagnosed high blood pressure, 8.5% exhibited abnormal blood sugar levels, and 45.9% presented with unhealthy lipid profiles despite being classified as healthy by conventional standards, the study reported.

These cardiometabolic abnormalities persisted after adjusting for variables including age, sex, physical activity, and study site, underscoring the potential significance of muscle composition as a distinct risk factor.

The research also highlighted the protective role of lean muscle mass, particularly in men. Higher lean muscle mass was associated with better cardiometabolic outcomes, while lower muscle mass correlated with increased risk factors. The sex-specific analysis, adjusted for gender differences, indicated that the protective effect of muscle mass was more pronounced in men, though elevated intermuscular fat was linked to higher cardiometabolic risks in both sexes. The authors cautioned that these findings do not imply women are unaffected but suggest differences in how muscle composition influences risk.

Physical activity emerged as a key modifiable factor affecting muscle composition. Participants with lower levels of physical activity tended to have more intermuscular adipose tissue and less lean muscle mass, according to the study. Researchers emphasized strength training as a relevant intervention to improve muscle health and potentially reduce cardiometabolic risk, based on the observed associations.

Dr. Ziegelmayer noted that the research team focused on a population without known disease to identify early markers of risk. He described the presence of substantial cardiometabolic risk factors in these ostensibly healthy adults as a significant finding. The study’s authors proposed that MRI-based assessment of muscle composition could serve as an imaging biomarker to augment traditional risk screening methods. They suggested that such imaging might be used opportunistically during routine MRI procedures to identify individuals at higher risk who might otherwise be missed.

The study was conducted across multiple centers and involved data collection in 2026, with the final analysis completed and published within the same year. The research received attention from outlets associated with the Radiological Society of North America (RSNA), which highlighted the potential for MRI to detect hidden risk factors in people who appear metabolically healthy by standard clinical measures.

This work represents an initial step toward integrating muscle composition metrics into cardiovascular and metabolic risk assessment. Future research may explore how incorporating intermuscular fat measurements into screening protocols could improve early detection and prevention strategies for heart disease and metabolic disorders.