I assume you mean something like this:
They bolt to the chassis rails (where the tow hooks come standard), and some even have a mid mount that bolts up under the lower grille opening into the metal of the front bumper bar. So to say they hit your body work would suggest that those this has happened to haven't secured it very well at all.
They offer limited protection - in fact, here (in Oz), we call them "Nudge" bars, as they will take the odd nudge, bang or scrape, but in a big impact, say with a Kangaroo or a cow, you'd be better off with a full 4 post bull bar like the one below:
I have voted with my feet on this one - I've just spent the weekend painting a second hand nudge bar; I went for a hammer coat charcoal finish, which should match the plastic trim on my XLT.