It is the Spirit that gives life to the flesh.
Why does my body die then?
The Spirit gives SPIRITUAL life.
We were spiritually dead in our sin. Unable to connect with God, without His life in us. When we are born again, the Spirit imparts spiritual life to our spirits so although our bodies are outwardly wasting away, we are being renewed in the inner man.
Sometimes the Spirit gives physical life in the form of a miracle of healing, but if eating actually flesh and blood gave actually physical life to the body, then anyone who are and drank would physically live forever.
Spiritual life connects us to God in our spirit. When the body then dies, the spirit is still alive and goes to be in His presence.