Sex may be a workout, but is it a truly aerobic one? I was inspired by Em & Lo's post last week wondering just how many calories a sex session can burn. Perhaps unsurprisingly, there's not a lot of research that's been published on the subject, though that hasn't stopped some folks from making precise calculations. My research has revealed the following:

• Kissing: 1-2 calories per minute

• Foreplay: 1-2 calories per minute (makes me wonder what their foreplay consists of...)

• Sex: (generally defined here as intercourse): 2-12 calories per minute. Many estimates say 3-6 calories, and no less an authority than the Kinsey Institute estimates 6 calories per minute.

• Other activities (undressing, masturbation) are frequently discussed, but I can't find a reputable source for these estimates.

• For a more general idea, the Health Status calculator lets you put in your weight and how many minutes you spend on foreplay and intercourse to see how many calories you burned with your guy last night.

• A caveat--the more you weigh, in general the more you can burn.

You may be wondering what about caloric gain during sex? For the sake of completeness, the amount of calories you may take in from your partner's ejaculate is about 5-15. If you're using whipped cream or other treats, though, you'll have to add that up yourself.

So 200 calories at a clip? Possible, but not easy. The bottom line: In order to burn calories, you've really got to get your heart rate up--just feeling your heart race isn't enough. As the Little Book of Calorie Burning advises, think movement, think different positions, think energy, and think passion.