One of Pizza Hut's current offers is The Plank -- almost a meter of pizza in the form of three deep pan pizzas in a long square box. Clearly it's intended as food for a large group, but just how many people should you invite to the party if you don't want to absorb far more kilojoules than necessary?
You can choose any three deep pan pizzas from the Legends or Classics range, so the exact number of kilojoules will vary. Pizza Hut's online nutritional information also assumes a dough base rather than a pan pizza, so the figures supplied will be on the low side. The lowest kilojoule pizza on offer is the Hot N Spicy Beef, which has 5411 kilojoules. Multiplied by three, there are at least 16000 kilojoules on offer. Given the deep pan base and the fact that anyone ordering almost certainly won't repeat the inclusions, a figure of 18000 kilojoules would be conservative.
As Pizza Hut itself points out, the recommended kilojoule intake for an average adult is 8700 kilojoules. Assuming pizza is dinner and that you've distributed your kilojoules evenly across the day, this meal shouldn't account for any more than 2900 of those kilojoules. That number suggests that you would need at least six people to avoid pigging out (and eight would be a better choice to allow for variations in the size of individuals and the fact that bacon and cheese are hard to refuse).
That doesn't mean you shouldn't enjoy pizza once in a while. Just don't order The Plank if it's only dinner for you and your partner.