'I do' -- as long as you quit smoking: The health pre-nup is real

In an otherwise unmemorable film last year, a scene about a prenuptial agreement stuck out. The groom, on his way to church to be married, was still haggling over the details of his prenup. The biggest sticking point was how often he could expect to have sex with his new wife in exchange for agreeing to lose 10 pounds.

Seems like satire. People wouldn't actually write such things into a prenuptial agreement, would they? Well, they would, as it turns out.

Health-related clauses that dictate weight requirements, ban smoking or spell out a plan to get pregnant within a certain period are unusual. But as people become more health conscious, they are indeed starting to turn up, according to Raoul Felder, a prominent matrimonial lawyer in New York City.

And just like in the movies, some couples apparently think a legal document will improve their sex lives. Felder recalls that one couple's agreement stipulated the wife wouldn't have sex with her husband at all unless he lost 50 pounds.

But putting something into a legal agreement doesn't mean it's enforceable, attorneys say. Prenuptial agreements generally spell out how a couple will handle their financial assets if they divorce or one of them dies. By inserting lifestyle clauses, couples hope to set out a blueprint for their marriage, Felder says. But in the case of a clause that forbids someone from smoking, for example, "What's the consequence of not abiding by the agreement?" asks Violet Woodhouse, a certified family law specialist in Newport Beach, Calif., and author of "Divorce and Money." "You either live with it, or you divorce."

Increasingly, however, a health-related clause of another kind is finding its way into prenuptial agreements, Felder says, and this one can be enforced.

"Now, people want assurance that their health insurance will continue if they divorce," he says. With health care costs continuing to rise, this should come as no surprise. People are getting married for health insurance, so why shouldn't it play a role when they call it quits?