Western culture is obsessed with a variety of conflicting things. One of those obsessions is health. Perhaps from good motives connected with our duty to preserve life under the sixth commandment, or perhaps from other motives, a lot of Christians in Western culture have come to think that being healthy is godly, and that being unhealthy is sinful.
We're not talking about people who get cancer - but people who eat fast food, or fatty food, or sugary food, or who smoke. These people are told that the Bible tells them to live a healthy life. So, what does Scripture actually say?
Well, Scripture does say that there is value in bodily exercise, but it calls the value "little."
1 Timothy 4:8 For bodily exercise profiteth little: but godliness is profitable unto all things, having promise of the life that now is, and of that which is to come.
Moreover, there are general warnings in Scripture against glutton, sloth, and drunkenness. The following is a nice example of all three.
Proverbs 23:21 For the drunkard and the glutton shall come to poverty: and drowsiness shall clothe a man with rags.
But what are the usual prooftexts of the Christian Health movement? One is 1 Timothy 4:8, omitting the portion after "profiteth." The more popular verses, however, are the verse that says our body is a temple, and another one that describes bringing our body under submission.
Those verses, however, are being taken out of context.
1 Corinthians 6:13-20
Meats for the belly, and the belly for meats: but God shall destroy both it and them. Now the body is not for fornication, but for the Lord; and the Lord for the body. And God hath both raised up the Lord, and will also raise up us by his own power. Know ye not that your bodies are the members of Christ? shall I then take the members of Christ, and make them the members of an harlot? God forbid. What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh. But he that is joined unto the Lord is one spirit. Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body. What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own? For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's.
The point Paul is making is not to stay away from the doughnuts, but rather to avoid fornication. Paul is not concerned with sub-optimally healthy diet choices, but with immoral behavior.
1 Corinthians 9:23-27
And this I do for the gospel's sake, that I might be partaker thereof with you. Know ye not that they which run in a race run all, but one receiveth the prize? So run, that ye may obtain. And every man that striveth for the mastery is temperate in all things. Now they do it to obtain a corruptible crown; but we an incorruptible. I therefore so run, not as uncertainly; so fight I, not as one that beateth the air: but I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.
In this context, Paul is making an analogy between the preparations an athlete makes and the preparation that an evangelist makes. The expression "keep under my body, and bring it into subjection" is part of that analogy. The point is that our spiritual preparations should be as rigorous as the physical preparations of an athlete.
None of the above should be an endorsement of living in a way that takes no regard for one's health. We are to have a concern for our own life and the lives our neighbors, under the sixth commandment. That doesn't mean any particular health craze is good or right - or that trying extend our life through obsessing over diet or exercise is good or right. The point is simply that making health eating, drinking, etc. a priority is a matter of Christian liberty, not a matter of moral duty.