The mechanisms of bone loss involve a predominance of osteodestructive cell activity over bone repair. Age and gender are the most significant biological risk factors; perimenopausal women constitute the most susceptible population group. Hormone-related phenomena, such as pregnancies and lactational performance, as well as heredity and ethnic origin, are also associated with osteoporosis. Alcohol and caffeine have been linked with progressive bone demineralization. A reduced body mass increases the probability of fractures. Dietary factors, such as adequate intakes of calcium, phosphates, and vitamin D, exert a protective action while the effect of fluoride and dietary fiber is still controversial. A constant physical activity promotes an appropriate development and maintenance of bone mass and architecture.