I'm not a body builder, but I was a competitive powerlifter for awhile and still am a serious lifter now. In my experience, serious lifters of either gender (including myself) tend to have trauma from the past that got them into it and helped the hobby stick. Typically they were either fat, underweight, short, or weak; they felt looked down on; or some combination of these things, and they were angry about it. Alternatively, they felt powerless for some reason and they felt that lifting empowered them and gave them control.

As George Leeman (an accomplished powerlifter) once said: "to lift these kinds of weights is not a happy thing...you do not try and pick up 800 lbs and fucking look like you're going to fucking kill somebody before you do it because everything is fucking great".