The observed tightness of the mass discrepancy-acceleration relation (MDAR) offers us the most promising window into the fundamental nature of dark matter, and poses a fine-tuning challenge for models of galaxy formation in a cosmological context. In this talk I will show how this relation can arise naturally from suitable interactions between baryons and dark matter, without the need for feedback processes, modifications of gravity or radical alterations of the matter sector. Specifically I will show that the equilibrium configuration of disk galaxies follows the MDAR in regions where the gravitational force is dominated by dark matter. I will also discuss pressure supported systems such as elliptical galaxies, dwarf spheroidals, and galaxy clusters.