HR zones/ counting steps inaccurate?

[Jplant57]

Just replaced my trusty Charge 2 which I've had for years with  a Charge 4 and have multiple issues.

Weirdly the HR zones in the Charge 4 are totally different. In the two weeks since I've worn it the time in 'fat burn has decreased drastically.  Doesn't kick into fat burn until I've nearly doubled my resting heart rate. (resting HR 59 avg over 3 years/fat burn starts at 116 Also when I wear them side by side the Charge 4 is recording only slightly more than half the steps as the charge 2...what's up?

[LZeeW]

@Jplant57   I can help you with your heart rate zone question.  Your Charge 2 awards active minutes and your Charge 4 awards active zone minutes.  The equations are different and are described in this Help article in the "What are heart rate zones?" section.  In a nutshell, Fitbit uses CDC recommendations for activity.  The CDC changed its activity guidelines in 2018 and no longer recognizes active minutes.  Active zone minute heart rate zones are more consistent with CDC guidelines.

I don't have an answer for your step counting difference.  I used both models and never noticed a difference like yours.