A lot depends on the toppings. I have a feeling OP calculated it by the toppings they'd put on a pizza rather than what the typical fat person would consider normal. I checked on dominoes site and put together an order closer to what the average fat would get. Going heavy on the cheese and adding bacon and pepperoni resulted in a calorie count of 4,800 for an XL pizza. So 2,400 calories on half of it.  It's possible that they didn't go all out with cheese and bacon, but at this point I think we can all agree that anyone bragging about eating half an XL pizza probably would.