Bone mass generally peaks around the age of 30-35, and then starts to slowly decline at around age 50 in women (60 in men) when you start to lose bone mass faster than your body can grow it back. This happens to all adults, however critical loss of bone mass (osteoporosis) is much more common in women.This is because women tend to have lower bone mass to begin with, live longer on average (more time to lose to bone mass), and generally take in less calcium.his happens to all adults, however critical loss of bone mass (osteoporosis) is much more common in women. This is because women tend to have lower bone mass to begin with, live longer on average (more time to lose to bone mass), and generally take in less calcium.