Osteoporosis Prevention in Preadolescent Girls

This study will test an osteoporosis prevention program aimed at preadolescent girls between the ages of 10 and 12 who have not yet started their menstrual periods. Girls in this age group are adding large amounts of new bone to their skeletons. Adding more bone at this time of life can reduce a person\'s chances of developing osteoporosis (thinning bones) in later years. We will look at how this osteoporosis prevention program affects the amount of calcium in the girls\' diets, the amount of weight-bearing exercise they do, and their bone mass measured using ultrasound testing of the heel.