According to a research, having sex thrice in a week can help you loose 5 to 10 Kgs in 20 days. I mean very rigorous sex, not as simple as you generally do ( I am kidding, you are good ). But remember that too much sex can be unhealthy. So stay up to your limits and copulate.
You can even calculate how many calories you burnt while having sex with this simple sex calculator tool. And of course, this tip is not for you if you are single.