It doesn’t work for everyone.
In my case, my food choices are very important. That’s why I do keto a lot, actually. And my SO (who can’t eat low-carb) needs to be often hungry on his active lifestyle to keep his weight and he isn’t even slim (but not fat).
Now I have no problems with not gaining but losing, that’s tricky.
+20 kcal (or 200 or 400) doesn’t really matter to me, my metabolism can follow it. I don’t know where are my limits, once I suddenly ate +1000 kcal for a month, no gain at all but I probably would saw something in a year or if I was more slim… My current weight is very stable.
Another problem that not everyone can wait until serious hunger or other good reasons (I need some extreme determination to do it and it often backfires anyway. I need too big meals when really hungry, it’s much better to eat before). And eating to satiety isn’t so simple either. For me, it often takes a lot to reach satiation even on a good diet but subtle hunger may come twice a day - so I overeat easily. Or just eat enough not to lose any fat.
I can eat a ton of food and just getting hungrier - or in a better case, staying just as hungry as I was. Now I know what to avoid all the time but it’s still not easy. I can’t be the only one like this. If someone has very reliable hunger and satiation, at least on keto, good for them. I am a tad envious but not very much as there are way more unfortunate people than me…
I never dictated what my body should do, that approach is impossible and weird for me. My body has power over me, I shouldn’t piss it off
I want to be nice to it anyway, our relationship is good, I listen to my body and it tells me what it wants (lots of calories and keeping this 30lbs extra fat, apparently. no gain, no lose, THIS. but I will trick it somehow, I worked for such a method in the last several years). And I have my inner hedonist, inner rebel, my health-consciousness, my circumstances (it’s the least problematic as I have power on them)… I need to satisfy everything. It’s not easy but if I give up to lose fat on keto ever, I can have an easy time.
I will never give it up
And it’s not like I don’t have fun. I like challenges even if this one is a tad too much.