Don't sell yourself short, girls can be fickle about things like that. You can be slim and muscular or a bit thicccc and muscular and they will not want anything to do with you. It's all about chemistry.

Take that episode of Doctor who where the Matt Smith doctor became a flatmate of a heavier chap who had this woman he liked. There was a time where she was attracted to the doctor, because he met her when he was only wearing a towel and was doing stuff better than the guy. And in the end he won her over. (it was more about him admitting his love for her but that's beside the point.)

I mean, the whole dad bod thing is sort of in right now I guess, and It's not a set standard. Just don't be a downer and you are pretty much fine.