I think it is because of the higher fitness level of men. It is also because of the way that men are built and we have a higher percentage of fat in males than females.
I am not sure about this one, but I think it is because of a hormone called testosterone. There are several reasons for this. One is that if you think about it, it’s really hard to get a girl to be very macho if you’re not a macho guy. Also, some studies have found that girls who have the highest testosterone levels are much better at playing sports than girls with low levels of testosterone.