Muscle

As we age, our muscles generally decrease in strength, endurance, size and weight. Typically, we lose about 23 percent of our muscle mass by age 80 as both the number and size of muscle fibers decrease. These changes may be more the result of inactivity, poor nutrition, and chronic illness or disease than the result of age per se. Much of this decrease in muscle mass can be prevented by maintaining physical fitness.

Both men and women experience an increase in body fat with age. In women, body fat increases linearly from about 25% at age 25 to about 41% at age 74. In men, the increase in body fat is similar to that of women until age 50 when it slows. Even in those who do not gain weight as they age, the body fat increases as the lean body mass decreases. Exercise can reduce but not totally prevent this age-related increase in body fat. The distribution of body fat also differs by gender. In men, the increase in fat mass occurs primarily around the abdomen. In women, the increase in fat is more often found in the thighs.