Fitness trackers are terrible at counting calories, says Stanford study

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  • mikelombardo078
    mikelombardo078 Posts: 17 Member
    edited May 2017
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    My fitbit charge 2 seems to do ok in keeping my eating in line with mfp synced. Lost 90 lbs and I eat whatever it says I can most of the time. Mfp set at sedentary and the charge does the rest, keep it simple.
  • limex
    limex Posts: 81 Member
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    Are those all wrist models? I'd be interested to see a study on a Fitbit One or the Zip. I've always wondered how a wrist device could even record steps accurately, much less calories.
  • PowerliftingMom
    PowerliftingMom Posts: 430 Member
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    I only use my Fitbit for steps and just to get an "estimate" on calories burned. Not surprised by the study or any other studies I've seen. I've never relied on the machines at the gym for accuracy either because those are always off
  • mikelombardo078
    mikelombardo078 Posts: 17 Member
    edited May 2017
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    limex wrote: »
    Are those all wrist models? I'd be interested to see a study on a Fitbit One or the Zip. I've always wondered how a wrist device could even record steps accurately, much less calories.

    I wear both a zip and a charge 2 and by the end of the day my steps are usually within a few hundred and calories burned are within 1 to 200 with the charge 2 being a the higher probably because of the hr. I feel that is plenty adequate enough to continue the life journey. Too many of us over think all this.
  • Maxematics
    Maxematics Posts: 2,287 Member
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    Meh, mine is accurate. Of course nothing is going to be perfect but a good portion of fitness tracker inaccuracies are from user error.
  • ChelzFit
    ChelzFit Posts: 292 Member
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    Most of the time I find mine to be pretty spot on with my TDEE here on MFP. There are some random days that I end up with a high number of active minutes and I know for a fact I didn't have that many active minutes. I mainly use mine for steps and rely on my Polar HR chest strap for a more accurate reading during my exercise.
  • macchiatto
    macchiatto Posts: 2,890 Member
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    PowerliftingMom wrote: »
    I only use my Fitbit for steps and just to get an "estimate" on calories burned. Not surprised by the study or any other studies I've seen. I've never relied on the machines at the gym for accuracy either because those are always off

    This is pretty much true for me, too.
    I got my Charge 2 in March, at which point I was starting to reverse diet back to maintenance. I only eat back a fraction of the exercise calories/adjustment but as pp's pointed out, most of us did that with other calorie burn estimates for exercise, e.g. MFP's or the machines at the gym.

    MFP estimated my maintenance at 1810 cals/day as lightly active. I think Fitbit is estimating I burn an average of 2300 cals/day but my true maintenance seems to be closer to 1700-1900/day depending on activity level.

  • fitmom4lifemfp
    fitmom4lifemfp Posts: 1,575 Member
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    mikelombardo078 wrote: »
    limex wrote: »
    Are those all wrist models? I'd be interested to see a study on a Fitbit One or the Zip. I've always wondered how a wrist device could even record steps accurately, much less calories.

    I wear both a zip and a charge 2 and by the end of the day my steps are usually within a few hundred and calories burned are within 1 to 200 with the charge 2 being a the higher probably because of the hr. I feel that is plenty adequate enough to continue the life journey. Too many of us over think all this.

    Just wondering...do you have both synced to a single Fitbit account? Or do you use 2 accounts?
  • GottaBurnEmAll
    GottaBurnEmAll Posts: 7,722 Member
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    PAV8888 wrote: »
    So here is the thing.
    They measured a specific exercise burn.
    And the trackers and any other form of estimation are unreliable. Even measuring the oxygen is not 100% reliable.

    But my tracker is useful not because it measures a specific exercise accurately but because it measures​ my daily tdee impartially, automatically, without me having to overthink it, and with sufficient accuracy over time for me to make eating decisions with 99% confidence. Because over time I know that it is at best off by 4% when it comes to the whole day.

    Do I have to engage SOME brain power? Yes, when I changed trackers halfway through the day and when I changed time zones the tracker was substantially off and I had to figure out on my own that the extra 1000 Cal were not really there.

    By the way note that my 4% includes those incidents...

    Anyway. Yes. They are an estimate that you combine with your results and will only be as accurate as you make them (see accuracy of most peoples' food logging)

    This.

    I've calibrated mine (a simple adjustment of setting it so that it thinks I'm wearing it on my dominant hand) so that it gives me feedback in line with results and I don't really need to overthink things from here on forward IRT my TDEE.

    I got the tracker as a means of assessing my TDEE and did not just blindly accept that it was what the tracker spit out. I knew enough to track my food accurately and see how the tracker performed against the scale and make a small adjustments as needed.

    Trackers aren't terrible, they just require a little thought and common sense to use properly.
  • GottaBurnEmAll
    GottaBurnEmAll Posts: 7,722 Member
    edited May 2017
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    ninerbuff wrote: »
    I have a Fitbit Charge 2 and use it for 2 reasons: to tell time and count steps. The number for steps is for just one reason: to ensure that I'm at least being active throughout the day. If the steps are low, I move more.


    A.C.E. Certified Personal and Group Fitness Trainer
    IDEA Fitness member
    Kickboxing Certified Instructor
    Been in fitness for 30 years and have studied kinesiology and nutrition
    9285851.png


    One of the main reasons I got the Charge 2 was for the move reminders.

    I've been at this weight loss game a long time and two points were forefront in my mind. One was the issue of adaptive thermogenesis and the other was the fact that people who exercise tend to have lower NEAT throughout the day.

    The move reminders are there to counter those two issues on days where I feel demotivated. I need to move a lot for medical reasons, but that ten minutes every hour (at least) really does help keep my TDEE up and compensate for those two effects.
  • Silentpadna
    Silentpadna Posts: 1,306 Member
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    PAV8888 wrote: »

    But my tracker is useful not because it measures a specific exercise accurately but because it measures​ my daily tdee impartially, automatically, without me having to overthink it, and with sufficient accuracy over time for me to make eating decisions with 99% confidence. Because over time I know that it is at best off by 4% when it comes to the whole day.
    ...

    Anyway. Yes. They are an estimate that you combine with your results and will only be as accurate as you make them (see accuracy of most peoples' food logging)

    This is where the rubber meets the road for me. My Fitbit is giving me values that correspond with many of estimated values based on age, size and exertion based oh heart rate....and my corresponding deficit matches actual weight loss pretty close to predicted.

    So it's either accurate, or inaccurate to the same magnitude (and direction) as my intake inaccuracies.....

  • NorthCascades
    NorthCascades Posts: 10,968 Member
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    PAV8888 wrote: »
    NorthCascades wrote: »
    NorthCascades wrote: »
    PAV8888 wrote: »
    But my tracker is useful not because it measures a specific exercise accurately but because it measures​ my daily tdee impartially, automatically, without me having to overthink it, and with sufficient accuracy over time for me to make eating decisions with 99% confidence. Because over time I know that it is at best off by 4% when it comes to the whole day.
    For context, this relies a great deal on your behavior, which sounds remarkably consistent from one day to the next, and may not work for many people.
    PAV8888 wrote: »
    No, what it relies on is the accurate measurement of food intake and weight change over time in conjunction with consistent tracking by the tracker.

    I must have done a bad job of explaining my objection if that's your answer. You're telling us your Fitbit is accurate to within 4 % of the gods' honest truth, but that isn't widely applicable. I don't know what you do for exercise but to use your example, the accuracy of your Fitbit depends on you not swimming. People who swim, and expect 96 % accuracy from their Fitbit, will be disappointed.
    PAV8888 wrote: »
    As to your friend.... they are missing the part where they have to adjust based on real world results.

    In my opinion, either a measuring device is accurate to some specification (no more than 4 % error was claimed) and its readings are trustworthy within spec, or it's not accurate and must be adjusted. It's like saying my thermometer is perfectly accurate, I just ignore it when it tells me it's 90 F outside if I can see it's snowing. At this point the Fitbit isn't what's accurate, it's the real world results that are accurate.

    Let's try this again:

    Fitness trackers are not accurate. Not within 5% or 10% without any adjustment for a lot of people. I am willing to grant you that.

    I will assume that you are willing to grant me that calorie counting is also not accurate. Not within 5% or 10% without any adjustment for a lot of people.

    So why have you been hanging around a calorie counting site for the past year and a bit?

    Did you somehow manage to find calorie counting useful in spite of the lack of absolute accuracy?

    This was an issue because earlier you claimed exactly the opposite:
    PAV8888 wrote: »
    That said...shrug re studies. Mine is accurate to 4% and that's good enough for my needs!

    Which is very clearly not true.

    I'm not saying we require absolute accuracy, I'm saying no fitness tracker is accurate to 4 % on its own. That's the only point of contention.
  • SusanMFindlay
    SusanMFindlay Posts: 1,804 Member
    edited May 2017
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    NorthCascades wrote: »
    PAV8888 wrote: »
    NorthCascades wrote: »
    NorthCascades wrote: »
    PAV8888 wrote: »
    But my tracker is useful not because it measures a specific exercise accurately but because it measures​ my daily tdee impartially, automatically, without me having to overthink it, and with sufficient accuracy over time for me to make eating decisions with 99% confidence. Because over time I know that it is at best off by 4% when it comes to the whole day.
    For context, this relies a great deal on your behavior, which sounds remarkably consistent from one day to the next, and may not work for many people.
    PAV8888 wrote: »
    No, what it relies on is the accurate measurement of food intake and weight change over time in conjunction with consistent tracking by the tracker.

    I must have done a bad job of explaining my objection if that's your answer. You're telling us your Fitbit is accurate to within 4 % of the gods' honest truth, but that isn't widely applicable. I don't know what you do for exercise but to use your example, the accuracy of your Fitbit depends on you not swimming. People who swim, and expect 96 % accuracy from their Fitbit, will be disappointed.
    PAV8888 wrote: »
    As to your friend.... they are missing the part where they have to adjust based on real world results.

    In my opinion, either a measuring device is accurate to some specification (no more than 4 % error was claimed) and its readings are trustworthy within spec, or it's not accurate and must be adjusted. It's like saying my thermometer is perfectly accurate, I just ignore it when it tells me it's 90 F outside if I can see it's snowing. At this point the Fitbit isn't what's accurate, it's the real world results that are accurate.

    Let's try this again:

    Fitness trackers are not accurate. Not within 5% or 10% without any adjustment for a lot of people. I am willing to grant you that.

    I will assume that you are willing to grant me that calorie counting is also not accurate. Not within 5% or 10% without any adjustment for a lot of people.

    So why have you been hanging around a calorie counting site for the past year and a bit?

    Did you somehow manage to find calorie counting useful in spite of the lack of absolute accuracy?

    This was an issue because earlier you claimed exactly the opposite:
    PAV8888 wrote: »
    That said...shrug re studies. Mine is accurate to 4% and that's good enough for my needs!

    Which is very clearly not true.

    I'm not saying we require absolute accuracy, I'm saying no fitness tracker is accurate to 4 % on its own. That's the only point of contention.

    All I know is that if my Charge 2 is overestimating my calorie burn, then I'm overestimating my calorie intake by exactly the same amount. Maybe that makes me a special snowflake. But, for me, having an external device back up the "that can't be right!" numbers that I was calculating from my calorie intake and weight loss was invaluable (in terms of peace of mind). It does also tend to increase my activity level as a result of the hourly "get up and move" reminders. And it's done the same for my husband. I beat his stair climbing record the other day, so you can bet he'll be climbing up and down the coulee on one of his lunch breaks to reclaim it! :smiley:

    For people who use the fitness trackers as motivation to move more (and only occasionally check the calorie burn out of casual interest), they're great. I can see that they might be problematic for people who would reward themselves every time they see a calorie burn. The gym is actually pretty bad for those people too. "I just walked on the treadmill for half an hour; time to get a venti frappu-something with whipped cream and a piece of cake."

    The only special set up that I did was entering my actual height, weight and age, and measuring my stride length on the track at the gym.
  • AnvilHead
    AnvilHead Posts: 18,344 Member
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    limex wrote: »
    Are those all wrist models? I'd be interested to see a study on a Fitbit One or the Zip. I've always wondered how a wrist device could even record steps accurately, much less calories.

    I used to own a Fitbit One, which I wore on my waistband. At that time, I was living in a place where I had to drive two miles of bumpy dirt road to get to the highway. The Fitbit would always log that drive on the dirt road as 1200-1500 steps and anywhere from 3-6 floors climbed.

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