Since my physical body belongs to Christ and He dwells in it as His temple, then I must reconsider how I think of myself.  I am not free to abuse what is His with the harmful.  What I eat and how much I eat is taking care of His body.  The gnostics separated spirituality from physicality, disconnecting bodily behavior from spiritual development.  The NT strongly affirms that you cannot separate what the body does from your spiritual development.

“Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, for you were bought with a price. So glorify God in your body.” 1 Corinthians 6:19-20 (ESV)