The term is fat blindness and is a genuine problem because fat gain is very slow and a lot of it hides in the back.
The only way a lot of people realize they are fat is if someone takes a picture of them and they have a moment “Wait am I really this big? Do I actually look like this irl?”
how it feels logging onto twitter dot com and seeing somebody ask if they'll gain weight on 500 cals and 40k steps after you genuinely binged 5000 cals