Are you aware of how calories are measured? They essentially set the food on fire and count how long it takes to go out.

Does our body digest things by acting like a furnace? No. There are different ways to extract energy from food and our body does things that aren't accounted for by the nutrtional facts blurb on the box. In some cases the food will just go straight through you, such as when you eat loads of fat. All those "calories" don't necessarily translate into x pounds on your body in new fat.