Are fitbit's numbers total crap? Hmmmm!!

Losingthedamnweight
Losingthedamnweight Posts: 535 Member
in Health and Weight Loss
So like a lot of other people, i like to rely on my fitbit to determine my tdee because to the laymen, TDEE seems like rocket science to figure out accurately. The weird thing is i always get numbers that make you go hmm. I'll get 7,000 steps in a day and my fitbit says "yeah you're awesome! Here's 2,000 calories for you ya big stud". And i chomp down my 2,000 happily. Then the next day, i'll get close to 9,000 and only eat 1800 and he says "whoa whoa whoa there tubby! Why you eaten' so many calories fer? You're 200 over! Dial it down buddy". WHAT?! Oh fitbit...our relationship is on the rocks right now...exhibit A

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Then...

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And it got just as confused today as it was the other day. Today i wore my tracker inside for a couple hours then took it off (and left it off for the rest of the day because i had to run out the house without it). So i only had 260 steps. Awesome. Even awesomer is it tells me at the end of the day i could've had 2,000 calories!

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Now i went back to the TDEE calculator and figured out the LOWEST level (sedentary) and it only told me with a 1000 calorie deficit, i should only have had about 1600 calories

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Is there something i'm missing? Am i going crazy? Er?

Replies

  • Losingthedamnweight
    Losingthedamnweight Posts: 535 Member
    I would also like to congratulate myself on actually posting pictures correctly without even checking what the code was. Yay for winging it!
  • AbnormalYak
    AbnormalYak Posts: 55 Member
    It's not only your step count that determines your TDEE. Look at other variables like stairs climbed. If you walked 9000 steps and every one was up a stair you'd burn a lot more kcals than if you walked 9000 steps on the flat, or down a hill.

    Also look at the daily active minutes. Again, 9000 steps running at 8min/mile pace burns more kcals than 9000 leisurely ambling steps.

    Finally, look at the amount of time you spend sedentary. There is a growing body of research evidence that time spent being sedentary is a health risk separate from time spent being active. I know it sounds mad. You'd expect one to be the simple inverse of the other, but it seems to not be that way. For example, I've seen evidence that shows boys are both more active and also more sedentary than girls - they spend more time than girls sitting still staring at TV, video games etc but when they're not doing that they tend to be running around, playing football, riding bikes etc.

    I don't know how Fitbit calculates your TDEE but I know it gathers data on all these three things as well as step count. So I don't find it surprising at all that you might have 2 days with the exact same step count but a different number of kcals to eat.

    One final point - it would be nice to think that you could precisely measure the amount of energy your body uses in a day with a gadget like the Fitbit, but it will never, couldn't possibly ever, be exactly accurate. And we often assume that you can accurately track the calories you eat with tools like MFP, going on the nutritional info on packaging and measuring everything precisely. But that will never be exactly precise either. AND ALSO even if you could do both these things precisely (which you can't) that this will determine precisely what weight you will be tomorrow/in a week/a year, but that's not exactly true either. These things are useful tools but they have inaccuracies, so don't rely on them absolutely. It leads to discouragement when you don't get the results you feel you were promised. Weight loss IS dependent on calories in-calories out, but you can't measure those things precisely. I use a Fitbit and MFP but if I don't see a result on the scale after a couple of weeks, I increase my activity or cut my intake a bit even if the numbers say I "should" be losing staying where I am.
  • wwhite72082
    wwhite72082 Posts: 36 Member
    From FitBit - https://help.fitbit.com/customer/portal/articles/898903-how-does-fitbit-know-how-many-calories-i-ve-burned
    How does Fitbit know how many calories I've burned?
    LAST UPDATED: SEP 15, 2013 03:09PM
    Your tracker and Dashboard show an estimated number of calories burned based on your BMR (Basal Metabolic Rate), which we calculate using the height, weight, age, and gender information you provided us with when you set up your Fitbit account.

    When you sync your tracker, Fitbit replaces your estimated calorie burn with your tracker's data. If you manually log activities, the calories burned by doing those will be taken into account as well.

    When you haven't synced your device or logged any activities, Fitbit tries to guess how many calories you have burned if you got out of bed, got dressed, went to your day job, came home, and did nothing much more than walk to your car.

    Once you start logging activities, Fitbit stops estimating and uses the data you've provided instead. The more you wear your tracker, the more accurate your calorie burn data will be.

    From MFP - http://www.myfitnesspal.com/help/faq/360-how-exactly-is-my-fitbit-calorie-adjustment-calculated
    Here is a more detailed explanation of the way we calculate the projected adjustment before a day is over:

    If you only have a partial day's worth of calories on your Fitbit, we calculate how many minutes are left in the day, and we use that to create a projection for how many calories you'll burn today.

    The calculation is: Fitbit calories so far for the day + (minutes left in the day / total minutes in a day) * (calories burned from normal daily activity)

    So for example, if it's 12 noon, you've burned 1200 calories so far today according to Fitbit, and your calories burned from normal daily activity on MFP is 2000, the projection is:

    1200 + (720 / 1440) * 2000 =
    1200 + (1/2) * 2000 =
    1200 + 1000=
    2200
    so the adjustment becomes
    2200 - 2000 (mfp calories burned from normal daily activity)=
    200

    It looks like your Fitbit must be projecting for the remainder of the day and coming up with some strange results. It probably isn't what you want to hear but, you may be better off enabling Negative Calorie Adjustments on MFP and ignoring the Fitbit when it comes to tracking calories consumed.
  • Losingthedamnweight
    Losingthedamnweight Posts: 535 Member
    It's not only your step count that determines your TDEE. Look at other variables like stairs climbed. If you walked 9000 steps and every one was up a stair you'd burn a lot more kcals than if you walked 9000 steps on the flat, or down a hill.

    Also look at the daily active minutes. Again, 9000 steps running at 8min/mile pace burns more kcals than 9000 leisurely ambling steps.

    You pretty much blew my mind just now. I don't know how i didn't think about that sooner. It makes total sense that fitbit takes into account all variables and mashes them together into one semi-educated guess everyday. Your comment is exactly what i was looking for and i can't thank you enough for that. I think i've been focusing too much lately on doing everything EXACTLY right for fear of not losing any weight at all or gaining some back. I've failed at this so many times that i'm almost positive i'm going to fail again and it scares me...i want to lose the weight and be healthy so bad and i keep sabotaging myself. I'm sick of it and it's weakening my faith that i can do it. ugh...anyway.

    Thanks for the comment. It really calmed me down. I'm going to focus on just getting out there and getting some exercise and eating what i believe is the right amount of calories
  • amflautist
    amflautist Posts: 939 Member
    Oh the time and money I have wasted in my life trying to understand my e-toys, buying dinners for them (batteries), making sure they were having fun (fixing the WiFi), and trying to educate them (reprogramming their stupid apps).

    Shoulda gone to a movie, listened to jazz on the radio, or called some friends using a landline instead. **Sigh**
  • amflautist
    amflautist Posts: 939 Member
    P.S. Losingthedam, I just looked at your profile -- with your attitude and sense of humor, you ARE going to be successful! Lol, ease up on the numbers (the easy part), figure out how to recognize and circumvent your trigger points (the hard part), and enjoy the journey. Your little girl is lucky to have a dad like you.

    Oh - and please send me a message when you post a pic of your new washboard!
  • AbnormalYak
    AbnormalYak Posts: 55 Member
    Thanks for the comment. It really calmed me down. I'm going to focus on just getting out there and getting some exercise and eating what i believe is the right amount of calories

    At the end of the day, that's the whole secret to this. Apps and gizmos are fun and can be motivating, but don't try to game the technology, instead game your own body. Eat a bit less, move a bit more than when you started. If you don't lose 1-2lbs a week eat even less/move even more. If you lose more than 1-2lbs a week eat a bit more/move a bit less. The tech helps track how much you are moving/eating because humans are really bad at judging these things, but don't get hung up on the exact numbers. It's the more/less bit that is important until you find the balance that gives you the magic 1-2lbs a week.

    I've been known to notice half way through the day I forgot to wear my Fitbit, and I thought "Dammit! All those stairs climbed for nothing!". It's such an easy trap to get hung up on the numbers on the screen and forget what really matters. I blame The Sims. I am not a Sim.
  • Francl27
    Francl27 Posts: 26,371 Member
    In my experience fitbit is all over the place for calories. Sometimes I walk 8000 steps and had 30 'active minutes' and it says I burned 2100 calories, sometimes I walk 10000 with 1h of active minutes and it says I burned 2000... I'd never link it to MFP, lol. I just use it (not so much lately) to give me an estimate on how many calories I burn during a week, then eat in average 20% under that.

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