Fitbit overestimating walking calories?

spyro88
spyro88 Posts: 472 Member
in Fitness and Exercise
Sorry if this has been asked before. Had a look but couldn't see it!

Today I did an hour of walking at a normal pace (just under 3mph. Mostly flat). Fitbit says I have burned 431 calories in this time (I was in "Fat Burn" zone for most of it). But MFP says 289! Both of them have my weight, age etc. but I don't sync them.

So which do you trust more for calorie estimates? Do you just opt for somewhere in the middle if you have two wildly different numbers like this?

I feel like the Fitbit should be more accurate because it's literally on my wrist measuring my heart rate, but 431 seems a lot for an hour's walking! What do you think?

Replies

  • skinnyrev2b
    skinnyrev2b Posts: 400 Member
    That's about commensurate with what it says for me too.
    Others have a calculation to accurately determine the calorie burn. Still others say that Fitbit is based on the average, so watch out if you're an outlier.
    Both would be correct.
    For myself (and ymmv) I ate half of the total fitbit exercise calories, and after originally losing 4lbs or so, I then plateaued for 5wks. I took the (to me) sensible advice to eat all the allocated calories for 4 weeks and work out from there if a) I'm putting weight on (over eating) b) losing as expected (1lb/week on average/4lbs over that period thus 500cal/day deficit overall or c)losing more than 4lbs thus need to eat more...
    I've lost 4lbs in the last 2 weeks...
  • sijomial
    sijomial Posts: 19,809 Member
    Heartbeat counters are not calorie counters and heartrate for moderate speed walking is often not a good metric at all, are you sure it's using HR and not steps/distance which would most likely be better for walking?
    e.g. My resting HR is 48 but I'm not burning less calories than when it was 60+ it's just my heart is better trained now and pumps more blood per beat.

    I use this calculator https://exrx.net/Calculators/WalkRunMETs and pick the net calorie option, MyFitnessPal unfortunately due to poor coding gives a gross calorie estimate which includes double counting the calories you would have burned anyway in that time slot.
  • spyro88
    spyro88 Posts: 472 Member
    edited February 2021
    @sijomial Thank you. Fitbit does say that it takes into account HR in calorie calculations (that's part of the reason I got it as I hoped it would be more accurate). So, I wondered if my heart rate is a bit higher because I'm not very fit and therefore the calorie calculation is a bit higher. But I don't know as it seems unlikely I burned over 400 calories on a walk.

    Thanks for the link. If I put it in there it says Gross 305, or Net 208.

    But what's the difference between Gross and Net? Is Gross also including BMR or something? (Edit: Sorry I just realised you answered this in your post!)
  • sijomial
    sijomial Posts: 19,809 Member
    Yes being unfit means your heart simply doesn't pump as much blood per beat as it could so it has to pump more often. It's part of the reason heart rate monitors need to be used with caution for calorie estimates, apart from fitness variation there's also massive variations in HR between different people of roughly the same fitness level.

    I don't know your device well enough to know if it is smart enough to only use HR where more appropriate and steps for walking.

    Gross and net is a bit more than just your BMR for that period but that's close enough for purpose.

    Another simplistic walking estimate is body weight in pounds X miles walked X 0.30 (efficiency ratio for walking) for a net calorie estimate for level ground walks.
    e.g. Say you walked 3 miles and weigh 200lbs your net cals would be roughly 180.
  • CurseofDolkite
    CurseofDolkite Posts: 31 Member
    sijomial wrote: »
    My resting HR is 48 but I'm not burning less calories than when it was 60+ it's just my heart is better trained now and pumps more blood per beat.

    I'm just starting today both with MFP and with a Fitbit Versa 3. Ulp...my heart rate while typing this is 98.

  • sijomial
    sijomial Posts: 19,809 Member
    CurseofDolkite wrote: »
    sijomial wrote: »
    My resting HR is 48 but I'm not burning less calories than when it was 60+ it's just my heart is better trained now and pumps more blood per beat.

    I'm just starting today both with MFP and with a Fitbit Versa 3. Ulp...my heart rate while typing this is 98.

    The only way is up - I mean down!
    Best of luck.
  • dragon_girl26
    dragon_girl26 Posts: 2,187 Member
    sijomial wrote: »
    Heartbeat counters are not calorie counters and heartrate for moderate speed walking is often not a good metric at all, are you sure it's using HR and not steps/distance which would most likely be better for walking?
    e.g. My resting HR is 48 but I'm not burning less calories than when it was 60+ it's just my heart is better trained now and pumps more blood per beat.

    I use this calculator https://exrx.net/Calculators/WalkRunMETs and pick the net calorie option, MyFitnessPal unfortunately due to poor coding gives a gross calorie estimate which includes double counting the calories you would have burned anyway in that time slot.

    Thanks for sharing this! I had always been doubtful of how accurate my Fitbit really was in calculating my walking workouts. Actually, though, when I input my usual daily routine in here it came out pretty darn close to what Fitbit says. Thanks!
  • CurseofDolkite
    CurseofDolkite Posts: 31 Member
    It's not even 1 pm and I just got a notice that I'm about halfway to my 150 "zone minutes." Does that mean it thinks I've been exerting myself this whole time? I've done nothing physically active today beyond driving to the store and back and going up and down the stairs. Plus chasing my cat once down two flights to see how high my pulse would get (something like 128).

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