Some of the same principles could be said about eating. Am I eating to keep alive or is it just pleasure not taking in weight increase or health? Taste and craving can be sinful too.
Paul goes on to say that even our body is a member of Christ. We are finding out in our day that even people who profess Christ are careless in this thing called sex. I am not talking about legitimate marriage. A healthy relationship this way is good. I am talking about co-habitation which people enter in without too much thought. Even when people who marry later are more apt to end up in divorce.
Paul is including all this because of the carelessness of the Corinthian Christians but there are epitomized portions of this among so called Christians in the USA today. In fact, it could happen to us if we get careless in our Christian life.
This ends with Paul bringing out that our bodies are the temple of God. We cannot desecrate the temple of God and get away with it.
Next we are bought with a price. What a price it was. The blood of Jesus. It was the purposeful death of Jesus on the Cross that bought us. Therefore, I glorify God because my body doesn't belong to me anymore.