This is the main reason of why being physically fit is important for being a follower of Jesus Christ, from Paul the Apostle's letter to the Corinthians, the first letter. Chapter 6:19; Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own;. So you see, your body is actually a temple of the Holy Spirit. Would it make sense to maintain it to be fit, and to not squander it and downgrade it with drugs and overeating? So you must be fit, for your body is truly a temple of the Holy Spirit, and we must make sure that it is healthy, just like God is.