FACT: Since about 98% of your bone mass is built by age 20, your past (rather than your genes) may give you a better glimpse at your future. If as a child you were active, a healthy weight, and ate many calcium-rich foods, you probably developed optimum bone mass. But if you were lax in bone-building behaviors and are still inactive, or you drink excessively, smoke, have lost weight rapidly, or have taken steroid medications for a long period of time, you may be at risk for brittle bones.
ACTION TO TAKE: The good news is that bone tissue remodels itself throughout life. At around age 40, cells that break down bone (particularly the spongy-looking inside of the bone that provides stability) become more active, while those that build bone slow down. But adopting healthy habits, like exercising regularly, eating right, losing weight gradually, and curbing alcohol and cigarette consumption, can still promote growth of your bones' strong outer shell and slow loss in the spongy part that is most prone to fracture.