How accurate do you suppose FitBit is?

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I have a FitBit flex that I use. How accurate do you suppose the calories burned are?

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  • RunsUponATime
    RunsUponATime Posts: 3 Member
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    I have the fitbit one and I find it to be very accurate. It pretty closely matches up with what mfp tells me
  • earlnabby
    earlnabby Posts: 8,171 Member
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    I recently did a test since I wanted to calculate my TDEE using my actual numbers. I added up my calories eaten and added 3500 calories for each pound lost over 30 days. I got a TDEE of 2683 calories. For the fun of it, I took the same 30 days and added up the TDEE calories Fitbit says I burned and got a TDEE of 2776. I would say that coming in with a difference of less than 100 calories is pretty accurate.

    The more you wear it, the more accurate it will be. I have had mine for over a year so it has a lot of data to use. I have a flex and wear it 24/7 unless it is charging.
  • Lyndonbearsmommy
    Lyndonbearsmommy Posts: 1,083 Member
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    Thanks!
  • ncfitbit
    ncfitbit Posts: 1,058 Member
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    earlnabby wrote: »
    I recently did a test since I wanted to calculate my TDEE using my actual numbers. I added up my calories eaten and added 3500 calories for each pound lost over 30 days. I got a TDEE of 2683 calories. For the fun of it, I took the same 30 days and added up the TDEE calories Fitbit says I burned and got a TDEE of 2776. I would say that coming in with a difference of less than 100 calories is pretty accurate.

    The more you wear it, the more accurate it will be. I have had mine for over a year so it has a lot of data to use. I have a flex and wear it 24/7 unless it is charging.

    Wow, this is brilliant! I want to try this. It will be good motivation for tracking every single item of food that goes into my mouth!
  • earlnabby
    earlnabby Posts: 8,171 Member
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    ncfitbit wrote: »
    earlnabby wrote: »
    I recently did a test since I wanted to calculate my TDEE using my actual numbers. I added up my calories eaten and added 3500 calories for each pound lost over 30 days. I got a TDEE of 2683 calories. For the fun of it, I took the same 30 days and added up the TDEE calories Fitbit says I burned and got a TDEE of 2776. I would say that coming in with a difference of less than 100 calories is pretty accurate.

    The more you wear it, the more accurate it will be. I have had mine for over a year so it has a lot of data to use. I have a flex and wear it 24/7 unless it is charging.

    Wow, this is brilliant! I want to try this. It will be good motivation for tracking every single item of food that goes into my mouth!

    I wanted to switch because my exercise is consistent from one week to the next and I liked the idea of averaging out my daily calories so I don't have days with too many to eat and other days with too few. I am more than 2/3 of the way to goal so I figured it would be a way to transition into maintenance too. Yes, you do have to make a point of being as accurate with your weighing, measuring and logging as is humanly possible. Also, to even out things like water weight fluctuations, etc. you should do it for at least 4 weeks.

  • ASKyle
    ASKyle Posts: 1,475 Member
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    I think mine is WAY off- If I was burning about 1950 a day like it says, while eating 1450, I would be losing a pound a week and I definitely am not.

    I only use it as a step counter and to get my 10k a day however I like.
  • zyxst
    zyxst Posts: 9,134 Member
    edited May 2015
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    Depends on the type of Fitbit. I felt my Ultra was spot on and was comfy using the numbers it gave me for my TDEE. I changed to the Zip and I don't feel the TDEE it gives me is accurate because I'd be losing more weight (eating 1800ish and TDEE is 3000, so should lose 2# a week but barely losing 2# a month), but I do believe the step count is correct.
  • Lyndonbearsmommy
    Lyndonbearsmommy Posts: 1,083 Member
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    zyxst wrote: »
    Depends on the type of Fitbit. I felt my Ultra was spot on and was comfy using the numbers it gave me for my TDEE. I changed to the Zip and I don't feel the TDEE it gives me is accurate because I'd be losing more weight (eating 1800ish and TDEE is 3000, so should lose 2# a week but barely losing 2# a month), but I do believe the step count is correct.

    I have a flex. This is my problem, my concern for the accuracy. I haven't lost weight in 3 weeks. I typically don't trust the calories burned so I try not to eat any exercise calories back and I don't log my other exercise. According to the calories burned vs calorie intake, I'm at anywhere from 500-1000 calorie deficit per day. I have the range because I do not own a food scale and am well aware that that could be a large discrepancy in my food loggin. I'm purchasing a food scale, but wasn't sure how much I should rely on the calories burned from FitBit.
  • charlieandcarol
    charlieandcarol Posts: 302 Member
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    I have a flex and find it seems reasonably accurate. I don't tend to eat back calories it gives me though unless I am hungry. I think that until you are as accurate as you can be with your food logging its more likely that the food logging is the problem not the fitbit. I guess once you are weighing all your food and are pretty sure what your intake is for a couple weeks, you might be better able to judge how well your fitbit is estimating.
  • shadow2soul
    shadow2soul Posts: 7,692 Member
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    I found the Flex and zip models to be under by about 200 calories on average. My Surge is pretty darn accurate.

    Surge 30 Day Avg Burn (can be found on Fitbit profile page): 2457
    30 Day Avg Intake (also found on Fitbit profile page): 1919
    30 Day Avg Deficit: 538
    Expected loss based on Avg Surge Burn: 4.6xxx lbs
    Trend weight loss: 4.6lbs (calculated by trendweight.com)
    If you look at my scale weight for the same time period as the 30 day burn is calculated from there is a 5lb change.

  • Christine_72
    Christine_72 Posts: 16,049 Member
    edited May 2015
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    I trust my zips steps, the calories it gives me is what I'm struggling with...
    I was happy eating around 1600 calories before getting my fitbit, but now I'm more used to 2000 calories because of those big fat exercise calories I can't resist eating back!! I rarely ever eat them all back, just most of them :tongue:
  • Christine_72
    Christine_72 Posts: 16,049 Member
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    Pu_239 wrote: »
    This is what you do, everyday you put in excel how many calories your fitbit tells you you burned, and you also input the calories you ate. Do this for a month, now you can see how much weight you SHOULD have lost according to fitbit, and how much weight you ACTUALLY lost.

    If you expected to lose 6lbs that month and lost 5. It's off about a pound a month. About 115 calories a day. Reduce your calorie goal by 115. Of course there are other factors such as water weight and stuff, but I think this is as close as you're going to get.

    That's a great idea! But it involves maths and data collection, something I must force myself to do, rather than run in the other direction :open_mouth:

  • Christine_72
    Christine_72 Posts: 16,049 Member
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    Awesomeness! Thank you :bigsmile: :+1:
  • cld111
    cld111 Posts: 300 Member
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    I have a Fitbit Charge and I find it to be VERY accurate. I've compared it with MFP's suggestions, and suggestions from using Fitness Frog and other TDEE calculators, and they all match up. I'm set on MFP to lose .5 pounds a week, but I seem to be losing 1 lb a week for the last 5 weeks. (I'm set to sedentary, and I pretty much eat back all of my exercise calories.) So far, so good!
  • Christine_72
    Christine_72 Posts: 16,049 Member
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    @cld111 I love reading posts like yours!
    Gives me more confidence in trusting the numbers :smile:
  • cld111
    cld111 Posts: 300 Member
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    @cld111 I love reading posts like yours!
    Gives me more confidence in trusting the numbers :smile:

    Yes, trust! And I recommend enjoying your food and your exercise! I'm not one of these 1200 calories type of people. I like to eat and I seem to eat about 2k or more a day. And I'm still losing. But I'm also pretty active because I like to be. I feel grateful for being able to be active, you know? Enjoy the journey. :)

  • shadow2soul
    shadow2soul Posts: 7,692 Member
    edited May 2015
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    Pu_239 wrote: »
    This is what you do, everyday you put in excel how many calories your fitbit tells you you burned, and you also input the calories you ate. Do this for a month, now you can see how much weight you SHOULD have lost according to fitbit, and how much weight you ACTUALLY lost.

    If you expected to lose 6lbs that month and lost 5. It's off about a pound a month. About 115 calories a day. Reduce your calorie goal by 115. Of course there are other factors such as water weight and stuff, but I think this is as close as you're going to get.

    That's a great idea! But it involves maths and data collection, something I must force myself to do, rather than run in the other direction :open_mouth:

    If you go to the Fitbit website on your profile page, your 30 Day Average Burn and 30 Day Average Intake are listed.
    m40dlezhsjus.jpg
    Hmmm...just realized the profile page rounds my height up. Weird. I wonder if they do that for the calorie burns or if they use the height that's actually in my settings.

    So take:
    30 Day Avg Burn - 30 Day Avg Intake = 30 Day Avg Deficit
    30 Day Avg Deficit * 30 = Total Deficit for 30 days
    Total 30 Day Deficit/3500 = Expected loss

    I then compare the expected loss to what I actually lost. If the expected loss is higher than what actually happened, I do a bit more math to see about how much it was off on a daily basis. If it's a small amount (less than 50 a day) then more than likely my logging was off. I will put the blame on my actual logging because I'm not perfect and I do eat places where I sometimes have to take a WAG at the calories. April was the perfect example of that. Good grief. I think I ate at this Asian Buffet every other weekend or something and who knows how many calories I consumed those days.
  • TimothyFish
    TimothyFish Posts: 4,925 Member
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    earlnabby wrote: »
    I recently did a test since I wanted to calculate my TDEE using my actual numbers. I added up my calories eaten and added 3500 calories for each pound lost over 30 days. I got a TDEE of 2683 calories. For the fun of it, I took the same 30 days and added up the TDEE calories Fitbit says I burned and got a TDEE of 2776. I would say that coming in with a difference of less than 100 calories is pretty accurate.

    The more you wear it, the more accurate it will be. I have had mine for over a year so it has a lot of data to use. I have a flex and wear it 24/7 unless it is charging.

    I'm glad to see that someone is actually trying to verify their calorie burns instead of just assuming that whatever is in the database is correct.
  • Lyndonbearsmommy
    Lyndonbearsmommy Posts: 1,083 Member
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    Pu_239 wrote: »
    Pu_239 wrote: »
    This is what you do, everyday you put in excel how many calories your fitbit tells you you burned, and you also input the calories you ate. Do this for a month, now you can see how much weight you SHOULD have lost according to fitbit, and how much weight you ACTUALLY lost.

    If you expected to lose 6lbs that month and lost 5. It's off about a pound a month. About 115 calories a day. Reduce your calorie goal by 115. Of course there are other factors such as water weight and stuff, but I think this is as close as you're going to get.

    That's a great idea! But it involves maths and data collection, something I must force myself to do, rather than run in the other direction :open_mouth:

    I am not sure if fitbit has an export function where you can export your data of the month. I am using a bodymedia fit(just started using it again). You can export the month data, it tells you how many calories you burned per day in excel. You can also do the same thing with myfitnesspal. using the export website...

    https://www.designbyvh.com/myfitnesspal-export-data/#.VV6STka6HlA

    Just takes roughly 30mins once a month.

    Thanks! I did calculate the calories burned for this month per fitbit and caloric intake and it was 20,000 deficit since May 1st (the exact number is at work so that's roughly what it was). I remember it being 975 calorie deficit per day which isn't accurate since I've lost no weight since then. Guess I just need to wait for the scale.