If I ate myself would I be twice as large or disappear?

First of all you could never entirely eat yourself, your head would be impossible to consume. Second of all, the mass would be equivalent, so you would neither gain nor lose anything. Third, who said you would disappear and why?!

the world ends, betch

u can't actuAlly fit ur self into ur self again just like trying to put 1 hairband inside the other it's impossible just like a bowl doin the same thing

Oh this again?!

You'd be dead, but thanks for playing.

Disappear

You would maintain your same weight overall, just in a greatly altered form. Wouldn't recommend it though 😋