What goes inside your body along with Mc Donald’s fries and burgers?? Author and Obesity Activist Julia Havey has been aging a McDonalds cheeseburger for 4 years. Find out what happens to this old burger. Fast food cheeseburgers age better than most humans. The French Fries still look fresh and retains its golden brown color whereas a normal potato turns brown after just 3 weeks. So what exactly is in this food and do you want to stuff that into your body??