FitBit Calorie Accuracy/Methods

L_Master
L_Master Posts: 354 Member
in Health and Weight Loss
Got a fitbit Charge HR for Christmas from the brother as part of a fun challenge for the family to stay connected and have some fun seeing who can get the most steps/calories burned.

Been wearing it to see what I think about it's metrics. Step counting seems to be pretty good.

My question is how do calories stack up. It feels a little high to me. Today I did just over 30k steps, with no non-walking exercise (i.e. cycling, weight training, etc.) and it gives me 3,945 so far with probably another 80 or so to come over the next couple hours before midnight. Which seems high.

Assuming I walk at 3.5mph and 120 steps/minute, that's 14.5 miles for the day. Less if I walk a little slower. Now, 10 of those miles were at a brisk walk over hilly terrain (10 mile walk, 1100ft elevation change), which leaves 4.5 flat miles. At 5'8" 150lb I'm no giant, and likely looking at 1500-2000 kcal for BMR estimate. That leaves 2-2.5k kcal from these 14.5 miles of walking, which is 140 kcal/mile...higher than most running estimates for people my size running.

Is this overestimation, or is there something I'm failing to account for in how fitbit is arriving at it's 4000 kcal number?

Replies

  • lovatt79
    lovatt79 Posts: 31 Member
    I got an HR for Christmas too, its been giving me a calorie adjustment of 1300 calories in MFP on top of the 1500 a day that is set by my 2lbs a week goal and sedentary setting. I was doing MFP before i got the fitbit and my goal was always 1500 calories a day and 10,000 steps. The fitbit is very confusing, its telling me i can eat a lot more than i feel is right so ive decided to just use it as a step counter and keep to my 1500 calories a day (minus the odd beer or 3 at weekends).

    Today it says i have burned 3400 calories and i have only walked 12,000 steps, with the fitbit system of 1000 calorie deficit to lose 2lbs a week i could eat 2400 calories today which is way over what i would feel comfortable eating and expecting to lose 2lbs.

    So in summary......i have no clue how this thing on my wrist works things out, im as baffled as you are and have been no help to you whatsoever.
  • L_Master
    L_Master Posts: 354 Member
    Hah, feel your pain for the moment. Someone probably has a good answer though. Figured if it could give me a better estimate of calories burned sans training it would move a little more out of the 'fun toy' category and into the 'useful device' category, as I have days where my activity outside of training can vary quite a bit.

    One thing I found to make sure of is setting it to 'Sedentary' rather than 'Personalized' in fitbit, as with the personalized setting it uses prior history to make assumptions about how active you're going to be the rest of the day. Sedentary just assumes you will sit the rest of the day, and adds calories when you don't.
  • Christine_72
    Christine_72 Posts: 16,049 Member
    Check out the FAQ section in our fitbit group.

    The numbers on your fitbit will be a bit wonky for the first day or two.. Until it learns your rhythm
  • Christine_72
    Christine_72 Posts: 16,049 Member
    Oops here's the link

    http://community.myfitnesspal.com/en/group/1290-fitbit-users
  • L_Master
    L_Master Posts: 354 Member
    Could still be learning, this is day 3 for me.

    That said, it still has to be pulling those calories from somewhere and as far as I know Fitbit uses the BMR formula (I think Mifflin-St. Joer?) and then adds calories from activity to it. Unless the BMR estimate is way off I can't see where aside from activity level fitbit is trying to add in calories from.

    Interestingly, for activities like cycling where it takes HR data and tries to calculate calories it MASSIVELY underestimates, on Christmas I rode 2 hrs at avg HR 130 and it only gave me credit for 1200 kcals, almost a full 40% off the actual 2,018 kcal I did burn. Of course, that's somewhat expected because there is no way to calculate calories from HR alone with any accuracy. One person's output at 120bpm could easily be double another persons output at 120bpm depending on fitness and HR variability.
  • Protranser
    Protranser Posts: 517 Member
    L_Master wrote: »
    Could still be learning, this is day 3 for me.

    That said, it still has to be pulling those calories from somewhere and as far as I know Fitbit uses the BMR formula (I think Mifflin-St. Joer?) and then adds calories from activity to it. Unless the BMR estimate is way off I can't see where aside from activity level fitbit is trying to add in calories from.

    Interestingly, for activities like cycling where it takes HR data and tries to calculate calories it MASSIVELY underestimates, on Christmas I rode 2 hrs at avg HR 130 and it only gave me credit for 1200 kcals, almost a full 40% off the actual 2,018 kcal I did burn. Of course, that's somewhat expected because there is no way to calculate calories from HR alone with any accuracy. One person's output at 120bpm could easily be double another persons output at 120bpm depending on fitness and HR variability.

    When you're not doing step based activity, it's suggested you go to the fitbit dashboard and enter a manual activity for the start and end time of your exercise. Alternatively, you can press and hold the track button on the tracker and wait for it to vibrate, then do your non step based activity, then press and hold the track button when you're done with your session. You'll need to use the dashboard to edit the "workout" entry and change it to the appropriate exercise (cycling, or spinning, etc.)

    I am under the impression cycling gives a lower calorie burn than running since the machine is doing part of the work for you, but I never thought to do any of the math myself...
  • yarwell
    yarwell Posts: 10,477 Member
    Fitbit's activity adjustment is primarily accelerometer based, I don't have the HR version but for walking, running and cycling it works fairly well for me. Base calories are from your stats - on fitbit.com you can see 15 mionute timeslices that show your BMR it is using - in my case 17 calories per 15 minutes.

    30k steps is a lot of activity.
  • jswigart
    jswigart Posts: 167 Member
    I have tried several trackers. None of them gave me what I would call an accurate account of calories burned. They are good for comparing your amount of activity from day to day, but that is as far as I would go with them.
    J
  • lizetrombley
    lizetrombley Posts: 28 Member
    I have used a fitbit hr for the last two months. Followed it to the t and have lost 20 pounds. Its is higher than MFP but i wouldn't be losing if it wasn't pretty accurate ... Im 5.4 and average about 20 to 25k steps and burn between 3000 and 4000 a day. I don't know the math or anything, just that it has worked for me.
  • megwa2001
    megwa2001 Posts: 31 Member
    Fitbit hr is accurate after 45 days of use , 7000 calorie deficit in a week u may loose 1 kg weight

  • dujyandco
    dujyandco Posts: 90 Member
    L_Master wrote: »
    One thing I found to make sure of is setting it to 'Sedentary' rather than 'Personalized' in fitbit, as with the personalized setting it uses prior history to make assumptions about how active you're going to be the rest of the day. Sedentary just assumes you will sit the rest of the day, and adds calories when you don't.

    Where did you change this? I can't find it!
    Thanks for your help. :)
  • Pawsforme
    Pawsforme Posts: 645 Member
    I've been using a Fitbit Charge HR since August 3. As well as I can tell it slightly under-estimates my TDEE. That's comparing what it gives for TDEE to my calorie consumption to weight lost.
  • afatpersonwholikesfood
    afatpersonwholikesfood Posts: 577 Member
    I also get crazy burns - higher daily overall burns than MFP ever gave me. Even so, I'm starting to believe it more based on my rate of loss since I got it 4 weeks ago. Even if it is inaccurate, it's been a great motivator for increasing activity and is just plain nifty.
  • Maxematics
    Maxematics Posts: 2,287 Member
    L_Master wrote: »
    One thing I found to make sure of is setting it to 'Sedentary' rather than 'Personalized' in fitbit, as with the personalized setting it uses prior history to make assumptions about how active you're going to be the rest of the day. Sedentary just assumes you will sit the rest of the day, and adds calories when you don't.

    I'm echoing this statement. I've been using the Charge HR since July and it has helped immensely with my goals. I disliked the food part for the first week or so because it would say I could eat 500 calories more, then all of a sudden it would say 300, then I'd go to bed at night and wake up starving and see by the end of the day I could have eaten 600 more calories and lost weight. I changed the food plan to Sedentary and never looked back. It starts you off with very little calories and then you easily build them as the day passes.

    As far as accuracy is concerned, I've found my Charge HR to be extremely accurate. As of late, I've actually been able to lose weight on what it says is my maintenance, but I'm not going to complain about that. lol.
  • _wontbackdown_
    _wontbackdown_ Posts: 1 Member
    Nothing to add but holy smokes you got 30k steps??! That's amazing!
  • Colorscheme
    Colorscheme Posts: 1,179 Member
    I think the Fitbit is accurate. When I am completely sedentary, it sats my TDEE is 1600-ish calories, about. I'm 5'7", 158 lbs or so, female, and I am 31. Yesterday I took 16k steps and it said I burned 800-ish calories from all the walking I did, since my walking tends to be at a fast pace. This means my TDEE increased to 2500-ish calories.

    You're a male. You have more muscle mass. You're probably younger, too and with 30k steps done, you burned a decent amount of calories just from that.

    The Fitbit does get more accurate the longer you use it.
  • missblondi2u
    missblondi2u Posts: 851 Member
    I've only got the flex, but it's been pretty spot on for me calorie-wise based on my rate of loss over the last three months. I've never gotten close to 30K steps though!!
  • gramarye
    gramarye Posts: 586 Member
    For months, I've used the Flex's total calories burned for the day minus 500 for my deficit and have found it to work really well. (This sentiment has been echoed by my friend who uses the HR.) It works for me; I do all my food stuff in MFP, and check all of my numbers on the Fitbit app.
  • WinoGelato
    WinoGelato Posts: 13,454 Member
    I've had a Flex for about 2 years and have found it to be fairly accurate at estimating calorie burns, based on the fact that I successfully lost weight and am currently maintaining using it synced with MFP. People would look at my numbers (5'2 female, over 40, 123 lbs with a desk job) and think there is no way that the FitBit calories burned of 2300/day could be accurate - but my experience proves that they are. I'm no marathoner, I average about 15K steps/day and do some light weight training a few times a week.

    I do agree that it gets more accurate over time and that you have to sort of trust it and how it syncs with MFP, if you try to overanalyze where the numbers come from I think you'll drive yourself crazy. And that's coming from an analytical person who loves numbers!
  • L_Master
    L_Master Posts: 354 Member
    dujyandco wrote: »
    L_Master wrote: »
    One thing I found to make sure of is setting it to 'Sedentary' rather than 'Personalized' in fitbit, as with the personalized setting it uses prior history to make assumptions about how active you're going to be the rest of the day. Sedentary just assumes you will sit the rest of the day, and adds calories when you don't.

    Where did you change this? I can't find it!
    Thanks for your help. :)

    Go to the Dashboard then go to where you have the four tabs of food/activities/weight/sleep, select food, scroll down to food plan, select the blue gear in the upper right corner of that box, set to sedentary, enjoy!
    Protranser wrote: »
    When you're not doing step based activity, it's suggested you go to the fitbit dashboard and enter a manual activity for the start and end time of your exercise. Alternatively, you can press and hold the track button on the tracker and wait for it to vibrate, then do your non step based activity, then press and hold the track button when you're done with your session. You'll need to use the dashboard to edit the "workout" entry and change it to the appropriate exercise (cycling, or spinning, etc.)

    I am under the impression cycling gives a lower calorie burn than running since the machine is doing part of the work for you, but I never thought to do any of the math myself...

    Yea, that's what I did for the cycling. Was tracking it to see how it worked and did it that way. I was actually really pleased to see Fitbit integrates with strava so I don't even need the fitbit while I ride as I can upload from garmin -> strava which then automatically syncs with MFP/FitBit. Perfect :)

    As for calorie burn, for the average person cycling is probably going to be a little lower per hour than running, yes. But in my case where cycling is my main sport it gets pretty comparable. A typical brisk but comfortable riding pace for me usually is good for 900-1000 kcal/hr, same effort running is usually somewhere around 6:50-7:20 pace, which if we assume 110 kcal/mile would be around 930 kcal/hr...so pretty similar.

    Fitbit can count the running more accurately though because it knows the general metabolic cost of running, it knows steps I take, and it knows what I have set in for stride length for a typical run. Cycling it has only HR to go off, which tells you nothing without at least having a corresponding VO2 max figure.
    _wontbackdown_ wrote: »
    Nothing to add but holy smokes you got 30k steps??! That's amazing!

    Courtesy of a nice 12 mile walk and an active work day, yea.

    We are starting a family step challenge in a couple weeks and on the first day I'm planning to scare everybody with a 100k day. Gonna be a loooooonnnnggggg walk :)

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