Recent studies have shown that there is an interaction between fat and bone metabolisms. Adipose tissue secretes leptin and adiponectin to regulate bone metabolism. Leptin inhibits bone formation by activating the sympathetic nervous system, whereas the peripheral pathway of leptin shows a positive effect on bone formation. Opposite to leptin, adiponectin enhances or inhibits bone formation osteoblast in the central or peripheral respectively. On the other hand, osteocalcin (OCN) is decarboxylated and released from skeleton as the hormonal form of undercarboxylated-osteocalcin (ucOCN) to stimulate islets and fat to secret insulin and adiponectin respectively, thus to regulate energy metabolism. All these data indicate that there exist complex regulatory loops within fat and bone endocrine networks. In this review, we will elucidate the hormones and their receptors that mediate the communication between fat and bone metabolisms.