Really? Why?
It's not like you need to fake it to stack on weight if you're only eating McDonalds and always the largest serves.
I've heard there's salads and other token foods on the menu these days that aren't completely awful, and supposedly they even offer real coffee now (not sure if that was related to the bad publicity of their percolated coffee), but I assume the majority of it is still potatoes, fruit pies, battered fish and battered chicken deep fried in "shortening" along with burgers made from sweet bread, HFCS filled sauce, awful cheese and low quality beef?
Not to mention the thick shakes, soft drink, ice cream, sundaes, flurries and muffins of course.