Recent studies have indicated a novel function for skeleton unraveling its importance in the control of energy metabolism. In the present commentary, we speculate on the meaning for bone to act as a 'rheostat' modulating glucose metabolism, and how the primitive way of communication between bone and energy metabolism through switch on/off genes (like Ptprv) evolved to a more complicated 'talking' via gain/loss of hormones activity (like osteocalcin) by carboxylation/decarboxylation process.