I was having the same issue and found a solution. Hope it helps for everyone else...
1) Open the Gear Fit App (now called Galaxy Wearable).
2) Under "About Gear" click on the battery circle.
3) This will bring you to a page that breaks down the battery usage (takes awhile to load).
4) My battery usage was at 37% for "Steps". If this is the case for you, click on the steps icon. This should bring you to the version number and some options of uninstall or force stop.
5) Click on force stop.
My Gear Fit Pro 2 continued counting steps but the battery drain has stopped. Haven't had to charge it in a couple of days. Hope this works for others!!!
Found I was having this issue after the new update, battery was lasting about 5 hours. Did a factory reset on the device and set it all up again, so far the battery is at 90% after 9 hours (using a battery saver watch face, no vibrations, all connections off, heart rate and auto tracking on) Hope this helps!
I have found that the watch seems to reach some sort of critical memory issue after more than 2 weeks use where the battery starts to drain and watch gets less responsive. What I do is first fully charge it, then do a full reset and I find this always fixes it for another few weeks until the memory clogs up again. Once the battery starts to drain it almost fully discharges after 1 day to like 15%. But after reset it will again behave discharging to about 70% after 1 day.
I can barely make it through the night. I charge before going to bed and when I wake up I'm at 10%. I then need to charge twice during the day.
The thing spends more time on the charger than it does on my wrist.
I went from a fitbit that lasted a week to this. Pretty disapointing.