Do most skinny people over 30 have to think about what they eat literally all the time?

Nope! And I used to be fat so this isn’t an always-skinny person giving advice here. Also, I have an extremely slow metabolism so it’s very easy for me to gain weight.

But the best way to do it is to make eating well a routine, a habit. Also, be sure to eat higher-quality food. It’s far more satiating. And for me it’s important to have one day a week that I can (within reason) consume whatever I want to. If needed, measure portions. I have not needed to because I have ridiculous self control but I believe portion control can help if you do not.

And no, I am not hungry all the time and after the first few weeks I just got used to eating a lot less. (Again, I want to reiterate that it really, really helps to eat higher quality food, the best within reason you can afford.)

It’s certainly easier to intuitively eat your way to a miserable existence and early death, but that ain’t how I’d play it.