As the New York Post elegantly put it, "It's cookie versus nookie." A survey conducted by Fitness magazine showed that 51% of women polled said they'd "skip sex for a year if it meant they'd be skinny." The other 49% are sane, admitting that they'd rather "have great sex and be thirty pounds overweight."
In real life, of course, neither women nor men have to make these kinds of decisions; pretty much everyone knows that having sex is a healthy workout. That's why I would've liked it if, after asking the sex-or-skinniness question, Fitness immediately followed up with, "In what situation do you think you'd ever have to chose between being thin and celibacy?" And also maybe, "I mean, have you ever had sex before? That shit's awesome, you're stupid." But I guess that's why I don't work for Fitness.