Trusting fitbit numbers

aliciab307

Stats
24, F
196lbs~
37.6%bf~
Lift 4-5x/wk
Zumba 2x/wk
Walk 10-22k/day

Ok so I have the fbChargeHR. And for the past 2 wks my avg burn is 4.1k-wk 1, 4k-wk 2.

What is the margin of error for fitbit, if anyone knows? I'm wondering how much I should trust FB numbers. Lifting sessions are about 30-60 mins, zumba is about 45-60 mins

aliciab307

Bump

2essie

If you join the fitbit group you might find more people with the answer for you if you post your question there. Just a thought.

aliciab307

Thx. I'll check there

heybales

The calorie burn for the lifting should be manually entered, as HR based formula is going to inflate it.
HRM formula for calorie burn is only valid for steady-state aerobic exercise, same HR for 2-4 min.
Lifting if done right is just opposite of that.

For your other stuff, if the HRM formula is good for you, could be decent enough.

Here's study on a much nicer Polar HRM, with self-tests for needed stats, and the results using lab measured stats.

http://www.myfitnesspal.com/topics/show/459580-polar-hrm-calorie-burn-estimate-accuracy-study

And no - I doubt Fitbit is using formula nearly as good as Polar's.

Otherwise, the device underestimates for daily calorie burn outside of exercise.
It assumes sleeping level calorie burn for all non-moving time - BMR.
But when awake you burn more - RMR.
When standing not moving you burn even more.
When digesting/processing food you burn more, about 10% of calories eaten.
So outside of exercise - underestimated.