Gah.
I just don't like McD's anyway. Don't like the taste.
I will say (and I think I've said it here before) that I remember being 17 or 18 and eating two double quarters with cheese like they were nothing and not even feeling it. I could barely stomach one of them now.
But fast food isn't inherently terrible for you. Sure a lot of fast food places have things that are overloaded with calories and/or are just plain not very healthful for you, but bad eating habits are much more the cause of bad diet.
Personally, I like making my own burgers anyway though.