Most Helpful Guy
Generally if you have sex in the first date and he likes your personality, he will stay.
If you have sex on the first date and he doesn't like your personality then he won't stay.
Sometimes guys will lose interest in a girl if she sleeps with him on the first date but it isn't "the act" that makes him lose interest, it's "the implication".
The act is you sleeping with him on the first date, the implication is that he MIGHT assume that (you've had sex with a lot of other guys on the first date). That's what turns off SOME guys, what I wrote in parentheses. Like if a virgin had sex on the first date, most guys wouldn't see her as easy.