If you are Born Again the Holy Spirit lives inside of you. You are the temple of God the Holy Spirit! Paul is reminding the carnal, and immature Corinthian church that the temple of God is holy, and should be set apart for His use, and not mistreated or defiled in the world (1 Cor.3). Some people use this scripture to teach against smoking or over eating. That could be applied; but to keep it in context we should include candy, and every other thing that is bad for our bodies. What Paul was really talking about here was the abuse of our bodies that takes place when we use our bodies for immoral behavior. Our bodies are His Holy Temple, and we need to keep them pure from the disease of sin that is in the world.