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Just How Accurate are Fitbit's Calorie Estimates

calithulu
calithulu Posts: 25 Member
edited November 11 in Social Groups
Hey all,

I've seen a few postings around here (and elsewhere) discussing the Fitbit calorie estimates so I thought I'd link to a well written and approachable article:

http://runliftyoga.com/2014/05/how-accurate-is-a-fitbit-at-estimating-calorie-burn/

Disclaimer: I am in no way associated with the site.

There was an article published in the journal Medicine & Science in Sports & Exercise that compared the results. Sadly, I don't have access to the full text but you can see the abstract here:

http://journals.lww.com/acsm-msse/Citation/2014/10000/Validity_of_24_h_Physical_Activity_Recall__.18.aspx

From an excerpt of the full text, it appears that the Fitbit One was within 10.4% of the baseline calorie estimate and the Fitbit Zip was within 10.1%. Not bad at all!

So, there you have it. A user following her results using the Fitbit calorie estimates (an anecdote, to be sure, but not a bad one) and a published study looking at the accuracy of the devices (within 10.4%).

Replies

  • NancyN795
    NancyN795 Posts: 1,134 Member
    Which just confirms for me what I had already concluded...

    My recent lack of progress is tied directly to not adequately tracking calories in. It isn't that my FitBit is reporting that I'm burning more calories than I'm actually burning. I'm just plain, eating more than I record. I'm giving myself the rest of this week to slack off and then next week, I need to impose some real discipline.
  • heybales
    heybales Posts: 18,842 Member
    It also depends on how active and what type of activity.

    Average typical adult that is encouraged to walk more - very accurate estimates.

    Some gym classes or cardio 3 x weekly for 45 min - still pretty accurate.

    You start going nuts though like some of us like to do, those inaccuracies add up badly and you'll find yourself undereating way too much.
    And since all those workouts was probably for performance, just shot that in the foot by undereating too much.

  • marissafit06
    marissafit06 Posts: 1,996 Member
    RE undereating: at what point do fitbit steps could as exercise to effect caloric calculations? I am doing 12K steps per day + working out 4 days a week with 2-3 days of cardio (4-4:30 hours gross). I haven't been factoring fitbit steps as exercise though. I sometimes eat back calories over TDEE - 15% and am still losing weight. My TDEE is based on 3-5 hours of moderate exercise a week. I am wondering if this is because I am drastically underestimating my exercise.

    Thanks!
  • editorgrrl
    editorgrrl Posts: 7,060 Member
    I lost the weight and have maintained for more than seven months by eating back all my Fitbit adjustments. Therefore, my Fitbit burn is my TDEE (aka my maintenance calories).

    I never, ever log exercise in MFP. Exercise logged in MFP overwrites your Fitbit burn during that time.
  • marissafit06
    marissafit06 Posts: 1,996 Member
    I understand that thanks, but that's not my question. Most of my cardio is spinning and so my fitbit (flex) doesn't properly account for what I'm doing. I log my cardio into MFP using the exact time so that I don't double log. I haven't used the Fitbit for calories or as an exercise tool, rather as motivational tool to make sure that I am not sitting on my butt all day. My concern is that I'm over exercising by not compensating for my step calories in my mental determination of what I should eat.
  • heybales
    heybales Posts: 18,842 Member
    marissafit06 wrote: »
    RE undereating: at what point do fitbit steps could as exercise to effect caloric calculations? I am doing 12K steps per day + working out 4 days a week with 2-3 days of cardio (4-4:30 hours gross). I haven't been factoring fitbit steps as exercise though. I sometimes eat back calories over TDEE - 15% and am still losing weight. My TDEE is based on 3-5 hours of moderate exercise a week. I am wondering if this is because I am drastically underestimating my exercise.

    Thanks!

    Why are you estimating your TDEE from 5 rough levels when you have a device trying to give you infinite levels?
    You may have lucked out and by sheer coincidence happen to match.
    But the odds of that are not good.

    Get your weekly report from the email as to what you burned in total. Divide by 7 for average daily TDEE.

    Take off 15%, and set your eating goal.

    Unsync accounts, since adjustments will mess with that.

    And non-step based workouts like lifting must be entered on Fitbit so the TDEE is best estimate too.

    You are actually giving yourself more than 15% deficit the way you are doing it probably.
  • cmage101893
    cmage101893 Posts: 5
    edited February 2015
    um... what does TDEE stand for? lol
    Please clarify acronyms before using them =(
  • cmage101893
    cmage101893 Posts: 5
    cmage101893 wrote: »
    um... what does TDEE stand for? lol
    Please clarify acronyms before using them =(

    got it, nvm
  • jvaughn1031
    jvaughn1031 Posts: 38 Member
    I still don't understand mine (flex). All my settings match (1 pound a week, sedetary, etc.) for each site and I still end up with about a 100 calorie difference in what I have left to eat. Like right now, MFB says 800 and fitbit says 717. wtf?
  • editorgrrl
    editorgrrl Posts: 7,060 Member
    Ignore your Fitbit calorie goal and follow MFP's, eating back your adjustments.
  • jvaughn1031
    jvaughn1031 Posts: 38 Member
    Ok, sounds good to me! my fitness pal usually gives me more anyways. lol
  • heybales
    heybales Posts: 18,842 Member
    At the end of the day they should match, as long as MFP got a final sync from Fitbit.

    Because MFP is adjusting it's estimated daily burn to match what Fitbit saw, if they both subtract 500, you end up the same.

    Now, Fitbit only syncs over new daily burn when it increases by 100 or you have synced your device with new info.
  • jvaughn1031
    jvaughn1031 Posts: 38 Member
    Nope. they never end up matching. There is always a 100 calorie difference and my settings on MFP are: sedetary, lose 1 pound a week while my fit bit is set to lose 1 pound a week also. My weight is the same on each so I'm stumped?
  • heybales
    heybales Posts: 18,842 Member
    Check the MFP Fitbit calorie adjustment, clicking on the "i" for more info.

    Was last update really at midnight, and is it showing the final Fitbit daily burn that Fitbit shows?

    Mine rarely reaches midnight for final sync. Now, the next sync after midnight does correct the prior day.

    And when I say end of the day they should match, I mean literally, midnight.
    During the day Fitbit has couple options that has the ability to make them not match, plus the way MFP handles rest of the hours of the day.

    Hence the need to just follow 1 road to a destination - don't attempt to follow 2. Just a mistake.
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