已有許多病生理機轉被提出與「老年衰弱症」有關，其中「肌少症」被認為與衰弱有高度的相關性，而肥胖型肌少症也屬於一種肌少症；正常老化下肌肉質量會隨著年齡增長而下降；肌肉質量與強度的衰退，容易影響步態和平衡，進而容易跌倒，造成行動能力下降，促使衰弱速度加速；又，許多急、慢性疾病及老化的相關狀況，也會間接或直接誘發衰弱的產生；衰弱又會更進一步使疾病、肌肉質量及相關情況惡化，導致衰弱老人進入每況愈下的惡性循環。

Many pathophysiological mechanisms have been proposed to be related to "frailty", among which "sarcopenia" is considered to be highly correlated with frailty. Sarcopenic obesity is also the type of sarcopenia that is more likely to be overlooked. Under normal aging, muscle mass will decline with age. The decline of muscle mass and strength can easily affect gait and balance, leading to frequent falls and affecting mobility and accelerating frailty. In addition, many acute or chronic diseases related to aging can indirectly or directly induce the frailty. Frailty will further worsen the disease, muscle mass, and related conditions, causing the frail elder to enter a vicious circle of deteriorating.