1 Corinthians 6:13

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 (KJV)

Then: Corinthians recognized this as another contemporary slogan. Paul used "Meats for the belly" and "belly for meats" to match and explain "all things are lawful." He limited its intent to the physical world. While not always edible, meat has a purpose for a time. While not always healthy, the belly has a purpose for a time. Eventually, just by the structure and dominion of God's laws of nature, men are born, men die (Fee, p. 255). By extrapolation, the Corinthians applied this statement to all other organs - hands, head, eyes, sexual organs, etc. (Baker, p. 93). That didn't work for Paul. He set forth to show that the spiritual implications of those behaviors couldn't allow their continued existence. Spiritually, the life purpose of the body is to do the Lord's will by uniting with him in daily service and avoid union with idols of any kind. Theologically, idols include anything that keeps someone from putting him first and from being obedient to him.

Now: We look further into the "belly for meat" phrase to understand how it equals the ideas "not all things are expedient/beneficial or the idea of self-control? If the belly wants meat, meat and more meat, then the product is an obese, out-of-control eater. By the slow laws of nature created by the Lord, the belly eventually throws all of the body's other functions out of whack, allows diseases to attack, and finally produces death. The belly and the eaters are destroyed prematurely. Many people also abhor extra marital behaviors due to their coinciding diseases. That analysis is a side issue to Paul's main theological point.

Extra Source: The First Epistle to the Corinthians by Gordon D. Fee (Eerdman's 1987) online at http://books.google.com/books?id=XlBp10nUTXAC&dq=Gordon+Fee+Bible+commentator&printsec=frontcover&source=in&hl=en&ei=SwLNSu3nA4v6Mf2XlDo&sa=X&oi=book_result&ct=result&resnum=12#v=onepage&q=&f=false
Cornerstone Biblical Commentary 1 Corinthians (William Baker), 2 Corinthians (Ralph Martin & Carl Toney), ed. by Philip Comfort. Carol Stream: Tyndale House Publishers, c2006.