Causes of sarcopenia include the following: Decreased physical activity Decreased food intake Increased levels of cytokines (particularly interleukin-6) Decreased levels of growth hormone and mechano growth factor (insulin-like growth factor-3) In men, decreasing androgen levels Aging decreases basal metabolic rate (due mainly to decreased fat-free mass), total body weight, height, and skeletal mass; from about age 40 to age 65, mean body fat (as a percentage of body weight) increases to about 30% (from 20%) in men and to 40% (from 27%) in women.