Have you seen the 4 year old cheese burger (I think its over 6 years old now?)
http://www.youtube.com/watch?v=4IGtDPG4UfI
McDonald's food, like virtually all processed foods is packed full of preservatives and junk. The woman left the burger on her window sill for months, and nothing ate it! The bugs and rodents weren't interested because they knew it was bad news.
If you haven't seen it, watch the documentary called "Supersize me" where a guy eats nothing but Mcdonalds a month. The effects on his body were immense. His doctor was stunned at the demise in his health.
Another good documentary to watch is "Sweet Misery". Its about the artificial sweetner Aspartame. This stuff caused holes in the brains of lab rats as well as tumors. Part of the ingredient for it comes from a genetically modified strain of e-coli bacteria. What the bacteria poops out goes to make Phenylalanine, one of the components of Aspartame. Its in everything from drinks to sweets and cakes.