What age does your body start to decline?

A new study says the decline begins at age 50. Researchers at Duke University School of Medicine suggest that physical deterioration begins in the 1950s and worsens as we age, especially in people who don't exercise. Three things tend to happen to our muscles as we age, says Professor Reaburn. Men can gradually lose an inch between the ages of 30 and 70, and women can lose about two inches.

After age 80, it's possible for both men and women to lose another inch. What they found was a correlation between age and decreased muscle mass, but that doesn't mean that aging automatically reduces muscle mass.