There's a lot of petty optimization going on in the world of fitness and weight loss ... in reality you don't need a diet or a fitbit or a fashionable caveman lifestyle if you're just outside moving a lot.
A fitbit is a tool to remind you to be moving a lot, by measuring, tracking, and exposing an objective quantification of your success in doing that. So, sure, if you succeed in doing it without such a tool, you don't need the tool. That doesn't make the tool a "petty optimization".
Appetite is like a thermostat that wants to maintain the status quo but one which isn't good at dealing with rapidly changing inputs.
If you want to change your body composition, you can do it entirely with the time you already use - eating - without having to do anything else.
I find fixing people's diet habits -- then pushing them into fitness once they have clean eating down pat as a habit, is much better than "just run it off"