I think there is a huge mental aspect with feelings of hunger that needs to be learned how to be dealt with. I used to work a pretty labor intensive job, and you would get hungry in the shift and would just have to tough it out with your stomach raging all day. After all of that experience, I can fast at will without it putting me out really (helpful during long days of airport traveling where the food is overpriced anyhow).

That's nothing compared to what some people had to deal with e.g. surviving famines. That takes some serious mental fortitude, but I would imagine after that experience you'd be perfectly fine if dinner was served late. If you ever read Siddartha, there's this part where the protagonist learned how to fast with the Samanas in the forest, and not everyone knows how to deal with that sensation and accept it as just another sensation in life.

On the other hand, I know people who get into this bizarre state if they are hungry, not long after whatever their normal mealtime might be sometimes. People joke around about being "hangry" but its a real thing for some people. I can see how if you haven't learned how to accept the sensation of hunger, and all you know with that feeling of hunger through your life is to immediately satiate that sensation, sticking to a caloric deficit would not be easy.