Sarcopenia is defined as a decline in muscle mass and strength and a deterioration of the physical functions caused by a decrease in lean body mass and an increase in fat with aging that is becoming a key condition of frailty in an aging society. Sarcopenia was assigned a disease code (M63.84) in the United States in 2016, with South Korea following suit by assigning it a disease code (M62.5) in the eighth revision of the Korean Standard Classification of Diseases in 2021. Discussions on the diagnostic criteria for sarcopenia are actively taking place in Asia, Europe, and other regions. On the other hand, although the presence of muscle loss is assessed, there are no established criteria for determining its severity. Furthermore, no effective treatment has been established because several factors affect muscle regeneration, including aging, lack of physical activity, endocrine dysfunction, metabolic diseases, chronic inflammation, and oxidative stress. Nevertheless, various candidate substances remain in clinical trial stages. This paper evaluated a clinical approach to sarcopenia by briefly reviewing its definition and diagnosis, summarizing the pathophysiology, and providing an overview of recent research and ongoing treatment developments.