Every food commercial, advertisement, and packaging in the US is currently protein obsessed. I just bought 3 burritos, and the most noticeable thing on the entire package is its protein content. TV commercials about waffles are advertising that they have X amount of protein per serving. The products in my jobsite’s vending machine have protein all over every package.
Did America have a protein thing recently?
Mostly no, but the mostly is because most vegetables aren’t as high in protein. If you eat protein rich vegetables the effect holds.
Some starches and fiber also have the effect, since metabolism is complicated. I believe potato is quite high on the satiety index, as are apples.
Basically it’s that your body just absorbs sugar and doesn’t spend time on it, so it doesn’t satisfy you. Carbs are pretty quick, but depending on the fiber content it can more than make up for it. Your body cherishes fat so it tries to get you to drink it. Protein is useful calories that take a lot of work to rip up, and they occupy space.
An apple and a bowl of lentil curry will fill you up.