In concrete and comprehensive terms, sarcopenia could be defined as a geriatric, multifactorial syndrome characterized by a progressive loss of muscle mass and strength, associated with severe consequences such as comorbidities, poor quality of life and mortality. It can be considered the result of different pathogenic mechanisms such as inflammation, malnutrition, hormonal imbalance, frailty, alterations in protein synthesis and degradation, mitochondrial dysfunction and physical inactivity. The prevalence increases with age, however, lifestyle, dietary habits, physical activity and the presence of diseases are factors that determine its evolution. Treatment of sarcopenia combines physical activity and diet. Physical activity is associated with increased muscle mass, preventing frailty and dysfunction, whereas the highest incidence of sarcopenia has been observed in sedentary older adults. A diet adequate in energy and, especially, protein helps to treat age-related decline in muscle mass, strength and skills.