Table 1.

Classification of sarcopenia by causes.

Primary Sarcopenia
Age-related	No clear causes other than aging
Secondary Sarcopenia
Daily living-related	Bedridden, lack of exercise, ataxia, weight loss
Nutrition-related	Malabsorption, gastrointestinal disease, appetite loss, lack of energy, low protein intake
Disease-related	Severe organ failure, inflammatory diseases, malignancies, endocrine diseases