I get nervous when I'm asked any question when there's a preconceived answer. Every church member I know, even those who smoke, seem to expect the answer to be "Yes. Smoking and chewing are sinful acts, besides being unhealthy." But preconceived ideas don't always reflect reality. And, as most kids will point out, there's really nothing about smoking in the Bible. How can we know for sure?
To make a determination, we have to look for inferences. The first inference some might make is to turn to the kosher food laws in the Old Testament. The kosher laws in Leviticus 11 and Deuteronomy 14 prohibit such foods as pork, rabbit, bear, shrimp, crab, lobster, clams, any meat served with cheese or other milk products (no Meat Lovers pizza or Quarter Pounders with Cheese!). Some assert these laws were written for health purposes and since tobacco is unhealthy it would have been prohibited. But the reality is these laws were made with no respect to health. Many of the non-kosher foods are quite healthy, while many kosher foods are rather unhealthy.
A second possible inference is the rather famous verse in 2nd Corinthians. There we read, "Do you not know that your body is a temple of the Holy Spirit within you, which you have from God, and that you are not your own?" (1 Corinthians 6.19). From this verse many have argued that Paul is insisting we take good care of our body because it is God's temple. The inference really isn't a bad one; however, the larger context of this passage specifies sexual immorality as the sin that pollutes the body: "Do you not know that whoever is united to a prostitute becomes one body with her? For it is said, 'The two shall be one flesh.' . . . Shun fornication! Every sin that a person commits is outside the body; but the fornicator sins against the body itself" (1 Corinthians 6.16, 18). Besides, Jesus said, "Listen and understand: it is not what goes into the mouth that defiles a person, but what comes out of the mouth that defiles" (Matthew 15.10b-11). Would that not include tobacco products as well?
However, for those kids (and adults) ready to embrace Joe Camel, the Bible does have a few things to say about obedience and about addictions. First, the Bible is quite specific about keeping the laws of the nation: "Let every person be subject to the governing authorities; for there is no authority except from God, and those authorities that exist have been instituted by God. Therefore whoever resists authority resists what God has appointed, and those who resist will incur judgment" (Romans 13.1-2). It is illegal for minors to purchase tobacco products, and in many communities it's illegal for minors to even possess tobacco products. Disobedience to the law is sinful.
Second, I know of only a few parents incompetent enough to actually condone smoking and/or chewing for their children; the vast majority rightly forbid it. Both the Old Testament and the New Testament command children's obedience to their parents: "Children, obey your parents in the Lord, for this is right" (Ephesians 6.1). Disobeying our parents is sinful.
Third, Paul writes that Christians are not to be dominated or enslaved by anything, except Jesus Christ. This includes alcohol, food, sex, relationships, greed, and anything else one might be addicted to -- which would include tobacco (nicotine). "'All things are lawful for me,' but not all things are beneficial. 'All things are lawful for me,' but I will not be dominated by anything" (1 Corinthians 6.12) -- which means there are a whole lot of smokers "addicted to sin" in our churches. Addictions are sinful.
So, is smoking or chewing sinful? If the law prohibits it, if your parents have prohibited it, and if you are, or would become, addicted to it, the answer is yes -- smoking is definitely sinful. But even if it wasn't, it wouldn't change the fact it's simply an unhealthy habit. With so many other health choices we have to make (Are we going to eat meat? Will we take the time to exercise? Do I really want that Twinkie?), why take up one more risk? Besides, WWJD?