posted by gut99% of the time it's all about a calorie deficit. Everything else is just BS intended to pray upon people's wallets. But I think exercise does help maintain your metabolism.
I tried a Fitbit four or five years ago. Was pretty useless, because I was already getting 20,000 steps or whatever at work (walking around a huge 900' by 500' warehouse a few times each day). Didn't do a thing for me.
My wife's workplace is using a group communication app called BAND to start an "exercise accountability' group, and I signed up as a spouse. The rules are, document a minimum of three 30-minute or more workouts each week (send a photo of you in action each day and tell what you did), and weigh yourself each week and send a photo of the scale to the workplace admin. You're eligible for various random prizes just for meeting those targets, plus other prizes for most weight lost in a 3-month BAND session (then a new one begins).
That subtle accountability has motivated us to start eating better and less (lots and lots of salads and proteins, much less bread and potatoes), and to start going to the gym in the afternoon and taking 30 minute walks throughout the week.
I've lost 25 lbs since the first of May, my wife's lost 20. It's both a combination of eating less, and stimulating your metabolism by working out. Got a ways to go, but the change is noticeable and we do feel better and can walk longer without falling apart.
A lot of folks at her workplace are getting into it. I'm impressed by the workout I've seen recorded by her co-workers.