I'm not opposed, as protein seems to be a good target to prioritize, but claiming there's a war on protein just seems so out of touch to the point of absurdity. It's practically the only thing that people care about right now.
The few friends I've known were attempting ketogenic diets over the years kept focusing on the protein side when the actual diet is supposed to be dominated by fat. They've all experienced kidney problems of one sort or another, surprise surprise!
You are being pretty fast and loose with your language here so I will alight what I think you are trying to say.
"Fill you up" I must assume means that you are implying the state of feeling "full" or satiated.
There is really only one study in the field of broad food source satiety: https://pubmed.ncbi.nlm.nih.gov/7498104/
Potatoes are the most satiating food at 323% that of white bread.
The second is Ling fish which is a source of protein, but another one of my assumptions is that when you say 'protein' I am doubtful you mean 'ling fish'. So assuming you mean a 2026 American definition of 'protein' you're probably referring to cow flesh (beef) which is only 176% of white bread, almost half of potatoes.
So, in the future I would suggest spreading the word and correcting your comment by saying "I mean potatoes do fill you up faster"