Frogman:
If you aren’t already accustomed to overeating (and bingeing,) you have to train yourself to do so. This can be challenging at first but once it becomes habituated, eating until you can barely move feels less uncomfortable. (That’s not advice, just my experience.)
You’re not only expanding your belly and body, but also your definition of what “full” means. Eventually you get used to feeling “full” most of the time—so that becomes your normal, comfortable state which facilitates more overeating and bingeing which makes you fatter.
This is so very accurate. When I was at the height of my stuffing habits and weight gain, I was packing in as much food as I could possibly hold repeatedly during the day and topping off every time the pressure eased up. Eventually, I perceived not being completely engorged as being hungry, and I couldn't sleep unless my belly was stuffed tight. Of course, I blew up and struggled mightily with easing up, but those were incredible times!