Lifestyle-related diseases such as diabetes mellitus, chronic kidney disease, and hypertension were previously considered to be unrelated to osteoporosis. However, recent investigations have demonstrated that lifestyle-related diseases have a significant effect on the regulation of bone metabolism. In addition, it has been also revealed that osteocalcin or fibroblast growth factor 23 (FGF23) , which is produced by osteoblasts, has an important role in glucose metabolism, fat metabolism, or calcium homeostasis. These findings suggest that bone is not only a target organ of hormones but also involved in regulating other organs as an endocrine organ. This review introduces such a bidirectional relationship between several lifestyle-related diseases and bone metabolism.