Actually, most of the people I see eating at McDonald's are quite healthy...
Supersize Me wasn't an actual documentary. More like a flawed experiment where the results of the experiment were tailored towards what the person wanted them to be. When you eat the fattiest thing on the menu three times a day, you're going to get fat. When you choose choices that are actually much healthier, such as the salads, you're not going to become like the guy in the documentary. Not unless you're REALLY sedentary. Like I am.
I'm not actually calling McDonalds Salads particularly healthy (though if you get the grilled chicken, which is essentially steamed and not cooked in grease, you're actually pretty well off) but they're healthier than Double Quarter Pounders.
Sorry, I just tire of "IT'S FUNNY BECAUSE HE/SHE IS FAT" pictures.