It is clear that after few generations the future moon man will adopt to the lower moon gravity (1/6 of earth's gravity). Here is a picture of such a person compared to the earthling.
After few generations on the moon, it is very much possible that the moon man is not able to walk on the earth any more, since he needs more muscles and stronger bones to do that. Maybe the moon should be a place where people should only visit maximum few years at a time and then return to the earth. Moon would be a great place for tourists that seek extreme sports and exotic places.