Hidden muscle fat may quietly raise risks for heart and metabolic disorders

• A new study suggests that higher levels of hidden fat within muscles were linked to increased risks of high blood pressure, unstable blood sugar, and unhealthy cholesterol levels.
• It also indicates that lower lean muscle mass was associated with worse cardiometabolic health, while higher muscle mass showed a protective effect, primarily in males.
• Low physical activity was associated with more hidden muscle fat and less lean muscle, highlighting lifestyle as an important factor in muscle composition and overall metabolic health.
• Many participants with no known health conditions were found to have undiagnosed risk factors, suggesting these issues can develop silently.

Hidden fat, also known as intermuscular adipose tissue, describes deposits of fat that build up directly between muscle groups or between individual muscle fibers.

It is considered as a form of ectopic fat, which refers to the accumulation of fat in nonadipose tissues, such as the muscles.

Previous research has highlighted that the infiltration of fat within muscle can have a negative impact on health, and may be associated with aging, metabolic conditions, such as type 2 diabetes, and cardiovascular events, such as heart attacks. Conversely, evidence indicates that lean muscle mass is associated with better health outcomes.

However, as the name suggests, unlike visible body fat, hidden fat is not easily detectable and can be difficult to measure accurately and reliably. Now, a new study utilizing advanced artificial intelligence (AI) to analyze muscle composition from MRI scans may be able to better identify hidden fat.

Adding to growing research, the imaging study, published in the Radiological Society of North America’s journal Radiology, suggests that fat hidden deep within muscles could be an underrecognized risk factor for cardiovascular and metabolic health problems, even in those who appear otherwise healthy.