Actually there is a reason for that. The fat in the cheeseburger doesnt make you fat, its the suggar. Because a regular coke will rise your bloodsugar and your body will produce insulin to lower your bloodsuggar. This reaction has the side effect, that it leads to storrage of fat in your body.
I also eat a lot of food, steak, burgers, fries, nachos, pringles and all that kind of stuff. Still I'm not a fatty, because I dont drink 2 gallons of coke every day!