Emerging evidence suggests that intermuscular fat (IMF) accumulation is associated with reduced muscle quality and increased risk of physical limitation. However, the impact and mechanism of IMF in sarcopenia or sarcopenic obesity (SO) are still unclear. MRI is a promising tool for early detection of sarcopenia and SO. This may translate to use in clinical trials and in future clinical practice, where quantitative assessment may become standard of care. . This study aims to study a new index that we term “IMF density”, shows promise as an important quantitative variable that reflects patients’ physical performances.