Fitbit overestimating daily calories?

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ekat120
ekat120 Posts: 407 Member
in Health and Weight Loss
I got a Fitbit the other day and have worn it for 3 full days now. The first day I took about 21,000 steps (including a 4 mile run) and it said I burned about 2,500 Cals. The second day I took 11,400 steps (no run that day) and it said I burned 2,200 Cals. Yesterday I took 32,000 steps (including 2 runs of just over 3 miles each--I did a lot of walking yesterday!) and it said I burned over 3,000 Cals.

When I calculate my BMR using the same formula Fitbit uses (Mifflin-St. Jeor I think) and adjust it for lightly active, it puts me at closer to 1,900 Cals per day. At 80 Cals/mi running, that would put me at about 2,200, 1,900, and 2,400 Cals. Am I really that much more active than that? Has anyone else encountered this issue? I triple-checked all my stats on their website, and I've entered everything accurately.
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Replies

  • boricua3177
    boricua3177 Posts: 192 Member
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    I'm glad you asked this because I am having the same issue. It seems like it is overestimating calories for me too. Hopefully someone has an answer for us. Saving my spot.
  • nicsflyingcircus
    nicsflyingcircus Posts: 2,409 Member
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    I don't count the calories my Fitbit tries to give me as exercise calories. I am currently about 170lbs overweight, having lost 46 and I mostly just use it to get an idea how much I am moving. I took 9200 steps yesterday and it tried to give me 500+ extra calories to eat! So, yes, I think it overestimates calories, so far as I can tell.
  • Booda101
    Booda101 Posts: 161 Member
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    The Fitbit calculates the total calories you'd burn in a day, including those just for existing. If you calculate your TDEE, the numbers should be similar.
  • bonniejo
    bonniejo Posts: 787 Member
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    You aren't lightly active. I would use very active or even extra active on the day you had two runs!
  • cwolfman13
    cwolfman13 Posts: 41,874 Member
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    Ummmm....do you really think going for 2x 3 mile runs and what not is lightly active? Keep in mind that you also just burn calories being alive...a whole bunch of them and Fitbit is going to include those in that number, it's not just the calorie you are burning from you deliberate exercise and steps taken...you burn a **** ton of calories just existing. On top of that you just have stuff like driving the car, doing the dishes, cleaning, etc...this stuff all adds to your "burn".

    One major issue here (as evidenced by some of the posts on this very thread) is that people vastly underestimate the caloric needs...very often people need far more fuel than they think they do. When I first started tracking this kind of stuff I thought, "no way I need 3,000 calories to maintain my weight...that has to be too much." Guess what....a bit over a year into maintenance and I need right around 3,000 calories to maintain my weight with my activity level.
  • ekat120
    ekat120 Posts: 407 Member
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    The Fitbit calculates the total calories you'd burn in a day, including those just for existing. If you calculate your TDEE, the numbers should be similar.

    I know that part (unlike apparently everyone on the Fitbit forums, which is why I posted here instead :smile: ) But I'm pretty sure my TDEE is closer to the low 2,000s (1,900 for lightly active, plus about 300-400/day average for running).
    You aren't lightly active. I would use very active or even extra active on the day you had two runs!

    I'm wondering about this. I add my runs separately because they vary from day to day and figure I'm lightly active when you don't count those, but I've definitely been walking more since I got the Fitbit (yay!). My (unfortunately extensive) experience counting calories and losing weight puts me at 1,900-2,000 to maintain without exercise, but maybe I've just been that much more active than usual the past few days? I'll gladly eat 3,000 Cals if I can! :love:
  • jkal1979
    jkal1979 Posts: 1,896 Member
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    I got a Fitbit the other day and have worn it for 3 full days now. The first day I took about 21,000 steps (including a 4 mile run) and it said I burned about 2,500 Cals. The second day I took 11,400 steps (no run that day) and it said I burned 2,200 Cals. Yesterday I took 32,000 steps (including 2 runs of just over 3 miles each--I did a lot of walking yesterday!) and it said I burned over 3,000 Cals.

    When I calculate my BMR using the same formula Fitbit uses (Mifflin-St. Jeor I think) and adjust it for lightly active, it puts me at closer to 1,900 Cals per day. At 80 Cals/mi running, that would put me at about 2,200, 1,900, and 2,400 Cals. Am I really that much more active than that? Has anyone else encountered this issue? I triple-checked all my stats on their website, and I've entered everything accurately.

    The Fitbit calorie total is your TDEE for that day. What did that come to when you calculated it?
  • ekat120
    ekat120 Posts: 407 Member
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    The scoobyworkshop.com calculator gives 2,110 for 3-5 hrs/wk of moderate activity (I run, mostly at an easy pace, 4-5 hrs/wk). 5-6 hrs/wk of strenuous activity gives 2,348. Maybe I'm just more active than I think? :huh:
  • yarwell
    yarwell Posts: 10,477 Member
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    32,000 steps is a lot, 3 hours running or 4.5 hours walking approx for me. My fitbit would be up around 3,000 calories at that, though I only got there once - 10,000 is a high enough target for me.
  • WinoGelato
    WinoGelato Posts: 13,454 Member
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    Before I got my FitBit, about a year ago, I had calculated my TDEE using various calculators, MFP, etc. I always came up with numbers like 1,700-1,800 because I was thinking, "Sedentary, office job, with a daily walk or some additional exercise 2-3 times/week". Once I got my Fitbit, and started seeing how many steps I take and calories I burn, just from the normal day to day stuff, I realized I had been underestimating. I don't run, but I do average 14K steps/day and I do some circuit training a couple times a week. My average calories burned according to FitBit are about 2,100 - so essentially that is my TDEE. When I changed my activity settings on MFP to lightly active, and then active, it got my numbers much closer to what FitBit was saying - and my weight loss continued at a 0.5lb/week rate (when I took 250 cal deficit from my numbers) and then easily transitioned into maintenance. I've found FitBit to be very accurate, and I get to eat more food!

    TL/DR - trust the FitBit, eat more food.
  • BarbieAS
    BarbieAS Posts: 1,414 Member
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    I've seen this guideline tossed around (and, comparing my Fitbit TDEEs to the various charts, it seems dead on for me)

    Sedentary = <5000 step

    Low Active = 5000-7499 steps

    Somewhat Active = 7500-9999 step

    Active = 10000-12499 steps

    Highly Active = 12500+ steps

    And you think 32,000 steps is lightly active? :huh: Even if you back out 6 miles of running, that's maybe only 12,000 or so (give or take) of your steps, leaving you 20,000 of general activity....
  • EvgeniZyntx
    EvgeniZyntx Posts: 24,208 Member
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    I got a Fitbit the other day and have worn it for 3 full days now. The first day I took about 21,000 steps (including a 4 mile run) and it said I burned about 2,500 Cals. The second day I took 11,400 steps (no run that day) and it said I burned 2,200 Cals. Yesterday I took 32,000 steps (including 2 runs of just over 3 miles each--I did a lot of walking yesterday!) and it said I burned over 3,000 Cals.

    When I calculate my BMR using the same formula Fitbit uses (Mifflin-St. Jeor I think) and adjust it for lightly active, it puts me at closer to 1,900 Cals per day. At 80 Cals/mi running, that would put me at about 2,200, 1,900, and 2,400 Cals. Am I really that much more active than that? Has anyone else encountered this issue? I triple-checked all my stats on their website, and I've entered everything accurately.

    No, that is not the formula that fitbit uses. I don't know where you got that idea.
    Fitbit uses a proprietary calculation based or correspondence curves they have researched.
    You can read a little about that here : http://blog.fitbit.com/a-brief-look-into-how-the-fitbit-algorithms-work/

    (And at 3000) steps you aren't lightly active. My own calculation show the fitbit to be pretty close to what I achieve using other evaluation means. (Without going into metabolic testing methods)
  • DeguelloTex
    DeguelloTex Posts: 6,658 Member
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    32,000 steps would put me at about 18 miles.
  • ekat120
    ekat120 Posts: 407 Member
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    No, that is not the formula that fitbit uses. I don't know where you got that idea.
    Fitbit uses a proprietary calculation based or correspondence curves they have researched.
    You can read a little about that here : http://blog.fitbit.com/a-brief-look-into-how-the-fitbit-algorithms-work/

    (And at 3000) steps you aren't lightly active. My own calculation show the fitbit to be pretty close to what I achieve using other evaluation means. (Without going into metabolic testing methods)

    Thanks. That link was helpful. Yesterday was a bit of an anomaly, but I guess the consensus is that I'm more active than I thought. Or maybe just more active now that I have the Fitbit (which is the whole reason I got it, I guess!). I guess that means I get to eat more! Yay!
  • ekat120
    ekat120 Posts: 407 Member
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    32,000 steps would put me at about 18 miles.

    It was a little over 15 for me (5‘6.5”). I went to a street festival and had to walk back and forth to the car parked almost a mile away to drop off/retrieve stuff before and after the 5k. Plus I walked around the festival and to the store earlier in the day.
  • rebeccaplatt21
    rebeccaplatt21 Posts: 175
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    The Fitbit calculates the total calories you'd burn in a day, including those just for existing. If you calculate your TDEE, the numbers should be similar.


    ^^^ this!!!
    i don't think mine overestimates. i went for a 30 min walk and gave me an extra 300+ cals. i used another app to track the same walk and gave me almost exactly the same!

    i personally have mine linked to MFP and love seeing the cals in/ cals out....i think it works great!
  • rebeccaplatt21
    rebeccaplatt21 Posts: 175
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    Ummmm....do you really think going for 2x 3 mile runs and what not is lightly active? Keep in mind that you also just burn calories being alive...a whole bunch of them and Fitbit is going to include those in that number, it's not just the calorie you are burning from you deliberate exercise and steps taken...you burn a **** ton of calories just existing. On top of that you just have stuff like driving the car, doing the dishes, cleaning, etc...this stuff all adds to your "burn".

    One major issue here (as evidenced by some of the posts on this very thread) is that people vastly underestimate the caloric needs...very often people need far more fuel than they think they do. When I first started tracking this kind of stuff I thought, "no way I need 3,000 calories to maintain my weight...that has to be too much." Guess what....a bit over a year into maintenance and I need right around 3,000 calories to maintain my weight with my activity level.

    ^^ this allso! great explanation
  • DeguelloTex
    DeguelloTex Posts: 6,658 Member
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    32,000 steps would put me at about 18 miles.

    It was a little over 15 for me (5‘6.5”). I went to a street festival and had to walk back and forth to the car parked almost a mile away to drop off/retrieve stuff before and after the 5k. Plus I walked around the festival and to the store earlier in the day.
    That's fair. My general point is that you have obviously burned a crapton of calories on the days you've worn the fitbit. I'm not saying it's definitely accurate, but the numbers don't seem crazy, either.
  • WalkingAlong
    WalkingAlong Posts: 4,926 Member
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    Some time after 2009, Fitbit switched to the Mifflin-St Jeor formula for their BMR estimate, I believe.

    I agree with the person above who said your steps don't match your run length. It seems like you were very active even in addition to 7 miles of running in one day.

    A Fitbit was pretty accurate for me through 35 lbs. of weight loss in 2010. Now, if anything, mine seems to underestimate, but I'm older and smaller and less active, too.

    Also, do you have a Flex? Those are less accurate and some will think you're walking when you're typing and that sort of thing. Might be worth a quick typing test to see, or whatever you do for a living.
  • ekat120
    ekat120 Posts: 407 Member
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    Some time after 2009, Fitbit switched to the Mifflin-St Jeor formula for their BMR estimate, I believe.

    I agree with the person above who said your steps don't match your run length. It seems like you were very active even in addition to 7 miles of running in one day.

    A Fitbit was pretty accurate for me through 35 lbs. of weight loss in 2010. Now, if anything, mine seems to underestimate, but I'm older and smaller and less active, too.

    Also, do you have a Flex? Those are less accurate and some will think you're walking when you're typing and that sort of thing. Might be worth a quick typing test to see, or whatever you do for a living.

    Good point. I do have the Flex. I just tried typing (lots of that in my job), and it didn't appear to be counting. I've watched it in the car, which is another place I've heard people have issues, and it doesn't give me any steps then. Looking at the log, it seems on par with my activity, so I think it's counting the steps correctly. It just seemed like it was overestimating my TDEE based on those steps. But based on your and others' experience, It sounds like it's probably about right.

    I'm going to follow it for a while and see how my intake and activity match up with any weight changes.

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