Once made, bone is always changing. Old bone is removed in a process called resorption, and new bone is formed in a process called formation. From childhood until age 30 years, bone is formed faster than it is broken down. After age 30 years, the process begins to reverse: bone is broken down faster than it is made. However, bone loss that happens too fast can result in osteoporosis. Osteoporosis causes bones to become too thin and weak.

To prevent osteoporosis, you should focus on building and keeping as much bone as you can before menopause. You can do that by getting plenty of calcium and exercise.