Sorry - I found this today and had to pass it on. Nothing really to do with survival, more of a warning!

http://www.nypost.com/entertainment/16393.htm

I haven't been able to eat there in 15 years. We used to stop in H.S. on band trips, every time I ate there I would get sick that night. Tried once or twice in the years after H.S. but still got sick.

A while ago I read an article about this experiment (sorry, no link available). They provided additional information. That guy had to eat a meal composed by Mc Donald´s and he was only allowed to order a regular helping if he wasn´t asked whether he wanted a large one. Of course he was not allowed to leave any food. They thought that many people would act that way. That puts the gained weight in perspective.
I am aware that fast food is usually no healthy food. For that reason I don´t eat at those restaurants and I don´t recommend them either. I had some stops at fast food restaurants for rehydration. They actually offer low fat meals and low sugar beverages. The customers are not exactly encouraged to consume those however.
BTW:
Your post can easily be filed in the "stay healthy and stay in shape"-section. That´s definitely on topic and at least preparedness related. So thanks for the link.