Your bones help you move, give you shape and support your body. They are living tissues that rebuild constantly throughout your life. During childhood and your teens, your body adds new bone faster than it removes old bone. After about age 20, you can lose bone faster than you make bone. To have strong bones when you are young, and to prevent bone loss when you are older, you need to get enough calcium , vitamin D and exercise. There are many kinds of bone problems: Osteoporosis makes your bones weak and more likely to break Osteogenesis imperfecta makes your bones brittle Paget's disease of bone makes them weak Bone disease can make bones easy to break Bones can also develop cancer Other bone diseases are caused by poor nutrition, genetic factors or problems with the rate of bone growth or rebuilding