Can you be a non-theistic religious person?

A friend of mine who is part of a Christian tradition that he does not believe in the existence of God said to me that he is a non-theistic Christian. I have heard stories of people who, for example, identify themselves as Buddhist but do not believe in the supernatural. I don't know if I really agree with that. Is it possible to be religious and not believe in God or superhuman things? I would like to hear opinions about it.