Steps, Distance and Zone Minutes - What am I missing here??

[KatSyyz]

So I am trying to make sure I burn at least 2500 calories per day. Below are a list of my metrics and the number of calories I burned on that day. Something is just not adding up. I understand its not a perfect science/formula and i understand it should be taken with a grain of salt but there should at least be consistency in terms of how all the numbers yield calories burned. See my examples from a few of my days to see what I mean:

Day 1 - 20,666 steps, 13.63 km, 69 zone minutes - 2386 calories 

Day 2 - 15,284 steps, 9.96 km, 55 zone minutes - 2416 calories

Day 3 - 17,534 steps, 11.57km, 25 zone minutes - 2350 calories

Day 4 - 20,779 steps, 14.09 km, 101 zone minutes - 2543 calories

Day 5 - 19,116 steps, 12.55 km, 60 zone minutes - 2138 calories 

Day 6 - 15,901 steps, 10.05 km, 112 zone minutes - 2588 calories 

Day 7 - 15,579 steps, 10.49 km, 151 zone munutes - 2556 calories

So I someone cherry picked these days to highlight what i am referring to. On Day 5 (and Day 1) I burned the lowest amount of calories yet I had more steps, km and zone minutes than both Days 2 and 3. How does that make any sense? My weight (according to the app) was not adjusted so that cant be factored in. On Day 7 my steps were about average but I had the highest amount of zone minutes so that tells me thats the number that should affect calories the most but if thats the case then shouldn't Day  5 have resulted in a higher calorie burn, not lower, than Day 2 and 3? Also Day 6 and 7 were near identical in all metrics except zone minutes, Day 7 being the highest but yielding less calories burned than Day 6.

If someone can explain to me what other factors I should be looking at to contribute to overall calorie burn it would be very helpful because I am beyond confused now. 

[KatSyyz]

I should mention Its the Charge 4 I have. If that makes a difference 

[Baltoscott]

@KatSyyz — There really isn’t enough detail in the various metrics to predict how much any of them correlate with your daily calories burn.  As you probably know, 50% or more of the burn is based on your weight and represents what it takes to maintain that weight (on average) each day, whether you move or not (your BMR).  As you note, because you haven’t updated the weight metric, that doesn’t account for the change, but I mention it to point out that an extra 30 minutes of exercise doesn’t really have as great an effect on daily burn as you might think.  If you are breathing, you are burning calories.

Active Zone minutes is a new metric introduced with the CH4.  I honestly don’t know if it is factored into your calorie burn. But if it is at all, if you think about it that can’t be the whole story. Some minutes are more ‘active’ than others, and some active zone minutes are more intense than others.  If you are doing an all out sprint you will be in your ‘peak’ zone (worth 2 active zone minutes), but a minute at an easy jog will probably keep you in the cardio zone, which is also worth 2 minutes.  Obviously the peak zone minute burns more calories than the cardio zone minute, and that would be reflected in your daily calorie count, but the impact on your daily active zone minute count would be the same.  And if Fitbit recognizes an activity while all this is going on it will make some assumptions in its calorie burn equation based on the activity type (running will burn more calories at the same heart rate than cycling).

There is a similar issue with step counts and calorie burn.  There are steps, and then there are STEPS. You get more calorie credit when you are moving quickly (which generally means longer steps), than when you are moving slowly. Effort matters and will be reflected somewhat in the daily calorie burn just because your body is moving more.

In the end, though, you are right to take all this with a grain of salt. Fitbit can give you the illusion of great precision in your daily burn calculations, but every factor it measures is an estimate. For me, when I was in the overweight BMI category, it seemed to over estimate calorie burn by about 20%. I’m in the normal BMI category right now and it seems fairly accurate, but I usually just ignore what it says about calorie burn and try to stay consistent with how much I eat.  For the other metrics, steps, active zone minutes, floors, I try keep track of my historical averages and make sure I’m not dropping off as I get older.

[Heybales]

To add to excellent info above, another factor in what may seem like changing calorie burn rate per mile.

For walking and even running frankly - distance-based calorie burn would be more accurate than HR-based - but especially for walking or anything at the bottom of the aerobic exercise HR range.

So if some of these daily steps was causing HR to go high enough for a chunk of time, then the device would slip into HR-based calorie burn.

And be inflated.

Whereas other days it was totally spread out never a chunk of time looking like a workout - so always distance-based calorie burn.

So if day 2 had a specific walking workout, device could have slipped into HR-based calorie burn giving inflated values.

But day 5 was spread out through the day using more accurate distance-based burn.

I've seen similar happen.

Usually looking at the 24 hr daily graph for calorie burn will show these normal bumps in increased active, but then a really big bump for block of time showing what must have occurred.

It makes it easy to find in that manner.

Also, from what others have shown for data - the Zone minutes is merely for you to have some goals for that figure - it's not used for calorie burn.

[emili]

@KatSyyz hey there. did you get the answer you were looking for? do you need some additional info? how can we help? If you are all set, please make one of the replies as the best answer so someone with the same question can find it quickly.. thank you!