It has been known for some time that nutritional and lifestyle factors are of great importance in the development and maintenance of normal bone mass and remodelling. Recent studies suggest that hypovitaminosis D is frequent in children and adolescent persons, and may affect their bone health. Clearly, chronic eating disorders such as anorexia nervosa are associated with high rates of bone resorption and bone loss, and increased fracture risk. In obese patients weight loss is associated with changes in both bone mineral density and bone remodelling, although the pathogenesis of these changes is ill defined. Biochemical markers of bone remodelling are non-invasive and comparatively inexpensive tools to evaluate the two major processes of bone renewal: bone formation and bone resorption. Over the past 15 years, research has generated a number of novel and specific bone markers that enable us to investigate those processes even more closely.