Really? I can eat a whole Costco pizza, and I have a normal BMI. I'm male and tall, so that helps.

A whole pepperoni from Costco is a bit under 4000 calories, which isn't quite 2x my daily recommended intake (something like 3000 calories). So I can do it, I'll just be a bit full and that's all I should be eating that day.

Regular large pizzas are a lot smaller than Costco pizzas. A large from Domino's is apparently ~2200, so two large Dominos pizzas are comparable to one Costco pizza (a little more, but not a ton more).

So I could do it if I was really hungry, but I usually only eat about 3-4 Costco slices (around 1000-1250 calories).

Your stomach stretches out after a long enough time of eating like this and you have to eat even more to feel full. Pair that with the availability of highly caloric foods designed to make you crave them and it's a recipe for disaster.

Watch some "my 600lb life" and it starts to make sense. It's a slow boil, to be sure, but I think it can happen to anyone that isn't paying attention, who uses food and that feeling of fullness to cope with whatever negative feelings they have. I like Sean of steel (former 600lber), he gives some really good context in his react vids on youtube.

As an above average American, I can. I have eaten an entire pizza and then gone back for seconds multiple times. You're supposed to not feel hungry after you eat, but I lack that crucial sense.

I don't do that anymore, but that's only because I remind myself that it's not normal to finish an entire large pizza in one sitting and I'm weird if I do it

how? I can eat 7/8 slices at once then eat the 8th like 30m later