Bone metabolism is a dynamic process regulated by the coordinated activity of osteoblasts and osteoclasts, modulated by hormonal, genetic, mechanical, and nutritional factors. This chapter reviews the main signaling pathways involved in bone remodeling, including Wnt, RANK/RANKL/OPG, BMP, and TGFβ-Smad, and the contribution of mesenchymal stem cells to skeletal regeneration. The role of hormonal regulators such as PTH, vitamin D, sex steroids, GH/IGF-1, and cortisol is discussed, together with the impact of physical activity and the emerging function of myokines like irisin. Particular attention is given to the effects of metabolic conditions, namely type 1 and type 2 diabetes and obesity, on bone mineral density and fracture risk. Finally, the chapter examines the nutritional determinants of bone health, addressing the role of proteins, lipids, and carbohydrates, and the contribution of calcium, vitamin D, phosphorus, magnesium, and other micronutrients in the prevention of osteoporosis and the maintenance of skeletal integrity throughout life.