"Fitness trackers are largely inaccurate when counting calories, Stanford researchers say"

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  • WinoGelato
    WinoGelato Posts: 13,454 Member
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    I have a FitBit Charge HR (previously a flex) and it has always been accurate for me in that I lost the weight I set out to lose and am now maintaining, while trusting and eating back the exercise adjustments I get from FitBit on MFP.

    I'm also a 5'2 118 lb female with a desk job who has a TDEE of 2200, higher than calculators and MFP would predict.
  • CarlydogsMom
    CarlydogsMom Posts: 645 Member
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    These things are all tools; a fitness tracker is essentially another tool like MFP. You get out of it what you put into it. I think there are a cadre of people out there, probably quite a high number, that continue to want some easy answer; or at a minimum, a tool they think will allow them to not have to think about exactly what they're doing. Or, may be just starting on a weight loss life, and don't know the specifics, advantages, and disadvantages of tools like these. And that's fine; it's a start, and people will learn as they go.

    I look back to 2010, when I started MFP (no trackers other than sites like this one; or if so, very limited), and think about how I am now, and realize I've learned so much. That's because I really worked at this. Read, researched, tried new things, had my ups and downs, had all sorts of wow-moments, and most importantly, DID THE CALORIC MATH--I was willing to put in the time to figure out what was right for me.

    I now have a fitness tracker and I use it for a variety of things, but I don't track my food on it. And I know when I've had a low-step day, I don't need it to tell me that. BUT, it's helpful to see the weekly trend reports, a summary of my active minutes per day and how that compares to past weeks, and it does spur me to, say, walk a few blocks to the post office for a mid-afternoon break instead of driving by it on my way home. I like looking at my sleep patterns as well. And I like setting it to track some specific exercise just for kicks.

    But I know, based upon past self-assessments, thinking, learning, pursuing, and reading, that it's a tool that is probably best used to monitor trends and as a motivator if nothing else. They have their place.
  • sporangia
    sporangia Posts: 50 Member
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    +1 to Azdak

    Precision is not the same as accuracy.
  • HappyGrape
    HappyGrape Posts: 436 Member
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    Fitbit was freakishly accurate for me! I calculated 100 days of tracking, the deficit calories /7700, expected vs actual weight loss! It came that Fitbit overestimated about 30 calories a day, probably me forgetting little drop of milk in my coffee sometimes!

    I lost the weight I was hoping to.

    But I am not arguing that it will work for everyone. This was my experience.
  • genpopadopolous
    genpopadopolous Posts: 411 Member
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    My Fitbit isn't accurate- but it's consistent!

    I want to lose 0.5 a week, so when I am being super tight with logging I keep it set to 1.5 pounds a week and eat most of my activity back and it's perfect.

    Right now I'm having a tough time with my eating, so I have it set to 2 pounds to try to add a little cushion for the days I am sucking.

    I don't care if it's wrong, as long as it's wrong the same way every day.

    I mainly like mine because it keeps track of my splits and stuff for my runs. And I'm a numbers nerd, so I like the data. I find it motivating to see my resting heart rate get lower, my splits get faster, and the little fireworks when I hit my goal. It gives me goals external to the scale to focus on, which for me is great to keep stuck to it.
  • Azdak
    Azdak Posts: 8,281 Member
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    If a fitness tracker numbers are "accurate for you", it is important to keep in mind that this is more due to random chance than anything else. If you recognize a pattern and it works for you, that is great, keep doing it.

    But keep in mind that this is most likely not due to the fact that your particular tracker is more accurate or a better model than anyone else's. If you change your routine, or for someone else using that tracker, it make be a completely different experience.
  • dewd2
    dewd2 Posts: 2,449 Member
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    I wear a Garmin Vivo Move. It counts steps. That's it. Nothing else. Because I have my baseline setup accurately Garmin knows when I take more steps that normal and adds those calories to my daily allowance.

    When I run I use a Garmin Forerunner. Since running can be reasonably measured (distance and mass) it knows how many calories I burn and adds them to MFP.

    The trick to get this right is to spend the time to setup your stats properly. Once the device knows you, it can measure your burn very accurately.

    People get into trouble when they try to use their devices for things they cannot do. Your fitbit has no idea how many calories you burn doing your fitness class. Or Yoga. Or lifting. And no matter what the marketing department tells you, heart rate is almost completely meaningless.

  • The_Enginerd
    The_Enginerd Posts: 3,982 Member
    edited May 2017
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    dewd2 wrote: »
    I wear a Garmin Vivo Move. It counts steps. That's it. Nothing else. Because I have my baseline setup accurately Garmin knows when I take more steps that normal and adds those calories to my daily allowance.

    When I run I use a Garmin Forerunner. Since running can be reasonably measured (distance and mass) it knows how many calories I burn and adds them to MFP.

    You would think this is the case, but Garmin is always way high unless it has my HR data to use instead. Likewise with Strava, although Strava ignores HR in it's calorie calculations anyway so it's always off even with HR data available. It almost seems as though they are spitting out gross calorie burns instead of net or using an optimistic factor in the calculations.

    The formula: 0.63 * Miles run * Weigh in lbs = Net Calories Burned has worked well for me for years, and it is fairly consistent with Garmin's numbers when I wear my HRM. Garmin's calculation match on average, although since they are HR based, they are inconsistent due to effects of weather on HR. I always gets a high number when it's warm, or lower when it's cool/dark.
  • Verity1111
    Verity1111 Posts: 3,309 Member
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    WinoGelato wrote: »
    I have a FitBit Charge HR (previously a flex) and it has always been accurate for me in that I lost the weight I set out to lose and am now maintaining, while trusting and eating back the exercise adjustments I get from FitBit on MFP.

    I'm also a 5'2 118 lb female with a desk job who has a TDEE of 2200, higher than calculators and MFP would predict.

    Which is exactly why it is important to remember these numbers are all averages and there are exceptions.
  • dewd2
    dewd2 Posts: 2,449 Member
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    The_Enginerd wrote: »
    dewd2 wrote: »
    I wear a Garmin Vivo Move. It counts steps. That's it. Nothing else. Because I have my baseline setup accurately Garmin knows when I take more steps that normal and adds those calories to my daily allowance.

    When I run I use a Garmin Forerunner. Since running can be reasonably measured (distance and mass) it knows how many calories I burn and adds them to MFP.

    You would think this is the case, but Garmin is always way high unless it has my HR data to use instead. Likewise with Strava, although Strava ignores HR in it's calorie calculations anyway so it's always off even with HR data available. It almost seems as though they are spitting out gross calorie burns instead of net or using an optimistic factor in the calculations.

    The formula: 0.63 * Miles run * Weigh in lbs = Net Calories Burned has worked well for me for years, and it is fairly consistent with Garmin's numbers when I wear my HRM. Garmin's calculation match on average, although since they are HR based, they are inconsistent due to effects of weather on HR. I always gets a high number when it's warm, or lower when it's cool/dark.

    Since I almost always wear my HRM when I run I haven't really tested it without. Maybe I can do some testing next after my race this weekend. I did have to adjust the settings a couple times to get it right when I first switched to Garmin. After that it has been very accurate.
  • dewd2
    dewd2 Posts: 2,449 Member
    edited May 2017
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    So I managed to find a run without my HRM and compared it to a similar length run with it. My weight was within 3 oz for each run. Last October I ran 6.51 miles in 51:14. My HRM was dead or I forgot it (there's no data). My calorie burn was 731. In February of this year I ran 6.47 miles in 1:01:53. Garmin said I burned 829 calories for that one. So it gave me more calories for a shorter, less intense run with the HRM on.

    Bottom line, don't trust it. Figure out what works for you by trial and error and stick with it. Since I am able to maintain my weight (or lose if I want) while eating nearly all of my calories back I'd have to guess the Garmin with the HRM is more accurate. This kinda makes sense since they also include my VO2max in the equation (using the now defunct First Beat data). I'm guessing something like a normal activity tracker will not even allow you to enter your VO2max (assuming a non athlete would know or even care).

    Here's an interesting (but old) article from DC Rainmaker on Garmin's calculations.

    https://www.dcrainmaker.com/2010/11/how-calorie-measurement-works-on-garmin.html

    EDIT: Correction above. The newer HRMs use FirstBeat, not New Leaf. Too damned confusing...

    One more edit: FirstBeat doesn't care about the VO2max at all. But it does need an accurate HRM so most wrist models would not be sufficient (maybe none since it is based on time between heart beats or something like that... ).
  • MaddieZieglerFan25
    MaddieZieglerFan25 Posts: 8 Member
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    I always subtract 200 calories from whatever Google Fit says I burned, and sometimes eat those calories back if I feel like it. I figure assuming a tracker is off by 200 calories is a good margin of error.
  • Tacklewasher
    Tacklewasher Posts: 7,122 Member
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    DC did a decent review of the study. Points out where they went wrong in their methods. He doesn't disagree with the findings so much as how they got there.

    https://www.dcrainmaker.com/2017/06/thoughts-on-the-wearables-studies-including-the-stanford-wearables-study.html
  • MelanieCN77
    MelanieCN77 Posts: 4,047 Member
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    Trackers are tools that provide data to work with, we shouldn't be slavishly responsible to exactly what they say. I see that as a similar mindset of following a "fad" diet, where people want to leave the intellectual heavy lifting to someone else. My AW cals are a little overestimated, my Fitbit cals are a lot overestimated. Knowing that I adjust my habits and behaviour, and still find immense value in the data and the records. You can build up an understanding over time with their assistance, but you have to police yourself and be sensible and honest with yourself, too.

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