Oddly enough, I've come across spiritual/mystical/shamanic stuff of one sort or another that states both of the following propositions:

Men suck women's energy.

Women suck men's energy (specially during the sexual act).

Whole lotta energy-sucking going on! (grin)

Maybe it happens both ways. Maybe it also depends to some extent on the nature of the individuals involved.

Maybe there is a useful energy exchange. That would seem like a reasonable possibility to me, and one that would encourage people to get together for mutual benefit. Nature certainly seems to think so, judging by what's going on out there with people and animals.