PMC3811714-EnM.2013.28.2.86.pdf - Review Article Endocrinol Metab 2013;28:86-89 http/ pISSN 2093-596X � eISSN

PMC3811714-EnM.2013.28.2.86.pdf - Review Article Endocrinol...

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86 Endocrinol Metab 2013;28:86-89 pISSN 2093-596X · eISSN 2093-5978 Review Article Sarcopenia and Sarcopenic Obesity Kyung Mook Choi Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea The aging process is associated with progressive loss of muscle mass and strength, as well as decline in physical functioning. Al- though consensus diagnosis has not been reached, sarcopenia is increasingly defined by both loss of muscle mass and loss of muscle function or strength. The cause of sarcopenia is suggested as multifactorial, including hormonal changes, inflammatory pathway ac- tivation, fatty infiltration, poor nutrition, and decreased physical activity. Sarcopenia is often associated with visceral obesity. Sarco- penic obesity in the elderly impacts metabolic complications and represents a major public health challenge in a rapidly aging soci- ety. Further research about sarcopenia and sarcopenic obesity may be needed to confront the influence of aging society in Korea. Keywords: Sarcopenia; Obesity; Muscle INTRODUCTION Aging is associated with a progressive loss of muscle mass, quality and strength, which results in a condition known as sarcopenia. In 1989, Rosenberg and Roubenoff [1] proposed the term sarcopenia, originating from the Greek words sarx (flesh) and penia (loss). Sarcopenia has been defined as “the age-associated loss of skeletal muscle mass, which results in decreased strength and aerobic capacity and thus functional capacity” [2]. Lean muscle mass contributes up to 50% of to- tal body weight in young adults but declines with age to 25% at 80 years old [3]. After 50 years of age, approximately 1% to 2% of muscle mass is expected to be lost per year, and muscle strength decreases at an even greater rate [4]. Sarcopenia is characterized by atrophy of type II muscle fiber and reduction in muscle fiber satellite cells with aging [5]. Interestingly, young men have twice as much muscle mass as fat mass, where- as this ratio is almost reversed in older men [6]. Aging is also related to increased visceral fat mass, which is an important factor in the development of metabolic syndrome, type 2 dia- betes and cardiovascular disease. Sarcopenia and visceral obe- sity may have a synergistic impact on both chronic metabolic disorders and physical disability [7]. DEFINITION OF SARCOPENIA Several different definitions of sarcopenia and sarcopenic obe- sity have been proposed in previous studies. Baumgartner et al. [8] defined sarcopenia as a two or greater standard devia- tion (SD) reduction in appendicular skeletal muscle (ASM) divided by height squared (ASM/height 2 ) below the normal mean for a young reference group measured using dual X-ray absorptiometry [8]. Janssen et al. [9] proposed a definition of sarcopenia as skeletal muscle mass index (skeletal muscle mass [kg]/weight [kg] × 100) one or two SD below the mean for a younger reference group. Newman et al. [10] introduced an al-
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