A new study has found that hidden fat stored within muscles may increase the risk of high blood pressure, unstable blood sugar levels, and unhealthy cholesterol, even among people who appear healthy.
Researchers discovered that individuals with higher amounts of hidden muscle fat and lower lean muscle mass were more likely to show signs of poor cardiometabolic health. The findings also showed that people with greater lean muscle mass generally had lower health risks, particularly among men.
The hidden fat, known as intermuscular adipose tissue, refers to fat deposits that build up between muscle groups and muscle fibers. Unlike visible body fat, this type of fat cannot easily be detected without medical imaging.
Health researchers say hidden muscle fat is considered a form of ectopic fat, which develops in areas of the body where fat is not normally stored. Previous studies have linked excess fat within muscles to ageing, type 2 diabetes, heart disease, and other metabolic conditions.
The new research analyzed MRI scans from more than 11,000 adults who had no previously diagnosed medical conditions. Advanced artificial intelligence technology was used to examine muscle composition and measure both lean muscle mass and hidden fat levels along the spine.
Despite appearing healthy, many participants were found to have undiagnosed health concerns. Researchers reported that more than 16 percent had high blood pressure, while others showed unhealthy cholesterol levels and unstable blood sugar readings.
The study identified a consistent pattern showing that higher hidden muscle fat was associated with increased cardiometabolic risks, even after factors such as age, sex, and physical activity were considered.
Researchers also observed that lean muscle mass appeared to provide a protective effect against some health risks, especially in men. In women, muscle mass remained stable during early adulthood but declined more noticeably during middle age.
The findings also highlighted the importance of regular physical activity. Participants with lower activity levels were more likely to have higher hidden fat and reduced muscle mass.
Health experts say both aerobic exercise and strength training may help reduce hidden muscle fat while improving overall muscle quality and metabolic health.
Current health recommendations encourage adults to engage in regular physical activity each week, including both cardiovascular exercise and muscle-strengthening activities.
Researchers believe the findings could help improve early detection of heart and metabolic diseases by using muscle composition as an additional health marker during routine imaging scans.
They added that more studies are still needed to better understand how hidden muscle fat affects long-term health and how it can best be used in disease prevention.
