Board Thread:Naruto Discussions/@comment-4366149-20141202054544/@comment-4366149-20141202194422

Yes, the percentage of Yin and Yang, in sense of spiritual and physical energy, can be changed but that cannot be what Yin and Yang Release or Natures simply are, because that would mean everyone has both Yin and Yang Natures, which is not true. Two possibilities that I can think of are:

1. Yin and Yang natures are the ability to use only/mostly spiritual energy or physical energy to perform techniques.

2. Just as the basic natures are simply nature transformations applied to chakra to alter their properties, Yin nature and Yang nature are simply applied to spiritual energy or to physical energy, respectively, in order to alter their properties.