I only can eat with enjoyment during dialysis and it is because my system is being cleaned in the process and takes away some of blood sugar and protein compounds that my body needs and also it clears up my taste sensation and then my appetite returns. I use that window of opportunity to eat to my heart's delight until I cannot eat no more and feel satiated.
The more intense the cleaning the faster my appetite returns and also the more I could eat. But still I could not eat no more than two cups of rice because maybe of my natural capacity and fluids in my body that also contributes to my being full so I could not really eat like a king but only just like a pauper I might say.
Some people just can eat that much because they conditioned themselves especially with their stomachs because our stomachs indeed can stretch and our brains are only the limiting factor if we want more food or not.
When I was in my first year in middle school I was eating less than my classmates and one of them noticed me and I see them eating huge amounts of rice which is normal amount actually, it is just I am a small-framed student in those years until I also tried to eat like them, and so after a few months I could also eat much more than previously.
It is just a matter of conditioning and practice but of course anything in excess is bad and we could bust our internal organs like our pancreas or our hearts, so it is not really recommended to eat excessively unless you know the consequences of what you are doing.