In 1 Cor. 6:12-13, Paul speaks about the way we use our body. "I will not be mastered by any of my bodily desires".
Food is essential for our bodies; but if you want to be a servant of God, you must not allow yourself to be mastered by food. If you love food so much that you are mastered by it, you will never be a useful servant of God. You have to break free from that slavery. This is where fasting can help. It is not only our spirit, but our physical body also is a "member of Christ" (1 Cor. 6:15). So we must never use it for any immoral purpose. It must be for the Lord's exclusive use - our eyes, our tongue and every part of our body.
Here is a wonderful promise of God for the body - that I have claimed for myself for many years now: "The body is for the Lord, and the Lord is for the body" (1 Cor. 6:13). If you say, "Lord, my body is totally Yours, from head to foot - my eyes, my tongue, my everything," and mean it, then the Lord will be totally for your body. He will keep your body fit to serve Him as long as He wants you to serve Him. He will even preserve it from sickness. Even young people may faint, but those who give their bodies to the Lord Him will fly like eagles in the sky.
Our body is also the temple of the Holy Spirit (1 Cor. 6:19) - and so we must not defile it in any way. If you won't smoke or drink or commit adultery inside a church building, then you must not do any of those things in your body either - because the real temple of God is not any church building, but your body. "You have been bought with a price. Therefore glorify God in your body" (verse 20).
These nine verses (1 Cor. 6:12-20) together form one of the most wonderful portions of Scripture about how we should use our body and God's provision for it. I would encourage you to meditate on it, because we need a healthy body in order to serve God.
Many Christians talk about healing. But health is better than healing. Prevention is better than cure. It is better to eat less and be healthy, than to be a glutton, get sick, and then ask God for healing. Don't ask the Lord to be your Healer, ask Him to be your Health. Give your body totally to Him and say, "Lord, You are the Health of my body. As long as You want me to live on earth and serve You, I am available. I will glorify You in my body, because You purchased it for Yourself on the cross. My body belongs to You alone."
Our body is like a house that has been purchased by someone else - the Lord. We must vacate this house and let the rightful Owner now occupy it fully. It is a sin to continue to live in a house that somebody else has purchased. Hand over your body then totally to the Lord.