“They say that you burn as many calories having sex as you do running five miles. But who runs five miles in 30 seconds?!”

It’s an old joke, but there’s a lot more truth to it than most people realize.

It’s easy to forget in the heat of the moment that having sex is a form of exercise. Not only that; sex is a full-body exercise that burns a ton of calories in all the right spots to keep you trim and fit. Let’s break it down.

A study according to Prevention found that women burn an average of 69 during sex, while men burn an average of 100 calories. That might not sound like a lot right off the bat, but there are two very important things to consider.

First, where are those calories being burned from? Good sex takes a lot of work from your core and your glutes. Combined with lots of movement, that means that sex is more than just a strong cardio workout. It also builds a little bit of muscle in those key areas for your figure.

Second, it’s important to remember that those 69 and 100 figures are only averages, based on 20 minutes of sex. But the vast majority of people having sex on a regular basis last far longer than 20 minutes. If that timeline is extended just 10 more minutes, the average woman is burning 100 calories and the average man 150.

Put both of those pieces together and you have the perfect recipe for washboard abs and a well-toned butt. And since sex is an exercise just like any other, it is important to engage at least a couple of times a week in order to maintain your figure and improve your endurance. The longer you keep at it, the better you’ll look both in and out of the bedroom.