Wanna find out just how much junk is in that junk food? Use the McCalculator!
Actually, my standard order of a Quarter Pounder w/ Cheese, small fries and coke isn't awful (at 640 calories and 31 grams of fat, it's not that great either). The blasted grilled chicken sandwich (which is, by the way, bloody awful IMO) has more fat!
Now, loading up a large shake, a Big Mac, large fries, and one of those McFlurry things gives a much more impressive 100 grams of fat and a whopping 2340 calories. Now I think I understand at least one way monstrously fat people can manage to get that way.
Personally, I like Quiznos better, and it's probably better for me. But sometimes you just gotta have some fries.