A new study finds men burn up to 101 calories during sex compared to just 69 calories for women.
This is the first time science has been used to show difference in male and female calorie-burn during sex.
And it seems the reason for the difference is that, in most cases, guys are doing a lot more of the "work", the Daily Star reported.
It tallies with research by the sex toy firm Lovehoney, which found that 80 calories are used up during each intercourse session.
Researchers worked with 21 straight couples who were asked to measure their calorie burn every time they had sex.
They were asked to have sex in the privacy of their own homes on four separate occasions and to practise their usual sexual activities.
To that end, they were instructed not to use Viagra or any other performance enhancement drugs and they were told to avoid any unusual sexual activities.
During each sex session, the couples were told to wear an armband that could record the amount of energy expended.
On average, participants' sexual activity sessions lasted around 25 minutes, although there was a substantial range that went from 10 minutes on the low end to 57 minutes on the high end.
These numbers include time spent on foreplay as well as time spent on sexual intercourse.
Across the four sessions, male participants burned an average of 101 calories each time (or 4.2 calories per minute), while female participants burned 69 calories (or 3.1 calories per minute).
The research is published in the American scientific journal Plos One.