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Trusting fitbit numbers

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aliciab307
aliciab307 Posts: 370 Member
in Social Groups
Stats
24, F
196lbs~
37.6%bf~
Lift 4-5x/wk
Zumba 2x/wk
Walk 10-22k/day

Ok so I have the fbChargeHR. And for the past 2 wks my avg burn is 4.1k-wk 1, 4k-wk 2.

What is the margin of error for fitbit, if anyone knows? I'm wondering how much I should trust FB numbers. Lifting sessions are about 30-60 mins, zumba is about 45-60 mins
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Replies

  • madierdorf
    madierdorf Posts: 73 Member
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    I don't know but with my flex I changed to dominant arm and my numbers went down alot for steps. Not sure why. I struggle to reach 10000 usually between 6-8900 . I run ,do karate , taking the stairs instead of elevator ...it is curious I must say. Good luck and keep on going:-)
  • perseverance14
    perseverance14 Posts: 1,364 Member
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    It is always too low for mine, but I have a One, by about 200-300 most days.
  • aliciab307
    aliciab307 Posts: 370 Member
    edited March 2015
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    Thanks guys. Just wondering how much I should eat according to what fitbit says I burn. I wear my fitbit on my non-dominant arm and the settings match the same. Think I'll try dominant arm today to see what the numbers say.

    I will say that right now I'm eating 2700 calories and not gaining and sometimes I am hungry at the end of the day. I guess that alone could mean I am burning more than I think? I'm aiming for 1lb/wk so I was going to up cals from 2700 to 3400.
  • ILiftHeavyAcrylics
    ILiftHeavyAcrylics Posts: 27,732 Member
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    Mine estimates low for me, which is good because it gives me a buffer to be over my calories occasionally. Overall I've eaten back all of my fitbit calories and maintained (which is my goal) for 10 months or so.
  • aliciab307
    aliciab307 Posts: 370 Member
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    Tha
    ILiftHeavyAcrylics wrote: »
    Mine estimates low for me, which is good because it gives me a buffer to be over my calories occasionally. Overall I've eaten back all of my fitbit calories and maintained (which is my goal) for 10 months or so.

    Thanks for the feedback. Which fitbit do you have? And if a wristband which arm do you wear it on?
  • shadow2soul
    shadow2soul Posts: 7,692 Member
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    The best way to figure out it's accuracy for you is to follow it for a couple weeks (4-6) and see if your weight loss matches what is expected for your average intake/burn (fitbit displays 30 day averages on your profile page).

    For example:
    30 Day average Burn from Fitbit Surge - 2483
    30 Day average intake - 2006
    30 Day average deficit - 477
    477*30= 14310
    14310/3500 = 4.088...
    Weight lost = 4.7

    So for the past 30 days, mine hasn't been 100% accurate, but so far it isn't overestimating either.
  • aliciab307
    aliciab307 Posts: 370 Member
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    shadow2soul wrote: »
    The best way to figure out it's accuracy for you is to follow it for a couple weeks (4-6) and see if your weight loss matches what is expected for your average intake/burn (fitbit displays 30 day averages on your profile page).

    For example:
    30 Day average Burn from Fitbit Surge - 2483
    30 Day average intake - 2006
    30 Day average deficit - 477
    477*30= 14310
    14310/3500 = 4.088...
    Weight lost = 4.7

    So for the past 30 days, mine hasn't been 100% accurate, but so far it isn't overestimating either.

    Thanks. I'm going to start that today. Just afraid of eating 3400 cals! Do you wear yours on dominant or nondominant? I've been wearing mine on non dominant but trying out dominant today. Wondering how different the numbers will be for each arm.
  • thorsonej
    thorsonej Posts: 10 Member
    edited March 2015
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    shadow2soul wrote: »
    The best way to figure out it's accuracy for you is to follow it for a couple weeks (4-6) and see if your weight loss matches what is expected for your average intake/burn (fitbit displays 30 day averages on your profile page).

    For example:
    30 Day average Burn from Fitbit Surge - 2483
    30 Day average intake - 2006
    30 Day average deficit - 477
    477*30= 14310
    14310/3500 = 4.088...
    Weight lost = 4.7

    So for the past 30 days, mine hasn't been 100% accurate, but so far it isn't overestimating either.


    Interesting. I just did mine, and came up with similar results.

    30 day average burn: 3082
    30 day average intake: 2659 (all food is weighed, so this should be relatively accurate)
    30 day average deficit: 423
    423*30=12690
    12690/3500=3.63lbs
    Actual weight loss: 3.7lbs

    I'd say that's pretty darn accurate.

    For reference, I have a One.
  • lzepeda89
    lzepeda89 Posts: 33 Member
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    ILiftHeavyAcrylics wrote: »
    Mine estimates low for me, which is good because it gives me a buffer to be over my calories occasionally. Overall I've eaten back all of my fitbit calories and maintained (which is my goal) for 10 months or so.

    Same here. I know for a fact my calorie counts are under what I normally do, which is a good thing like they said it gives me a buffer.
  • retirehappy
    retirehappy Posts: 4,754 Member
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    aliciab307 wrote: »
    Thanks guys. Just wondering how much I should eat according to what fitbit says I burn. I wear my fitbit on my non-dominant arm and the settings match the same. Think I'll try dominant arm today to see what the numbers say.

    I will say that right now I'm eating 2700 calories and not gaining and sometimes I am hungry at the end of the day. I guess that alone could mean I am burning more than I think? I'm aiming for 1lb/wk so I was going to up cals from 2700 to 3400.

    That is a huge jump in cals. I suggest you try adding 100 cals per day and see what the results are. Are you trying to maintain, lose, or gain? See if you see a difference.

    You are very active are you hungry or just bored? Sounds like you ROCK your days. :)

  • aliciab307
    aliciab307 Posts: 370 Member
    edited March 2015
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    Lol
    retirehappy wrote: »
    aliciab307 wrote: »
    Thanks guys. Just wondering how much I should eat according to what fitbit says I burn. I wear my fitbit on my non-dominant arm and the settings match the same. Think I'll try dominant arm today to see what the numbers say.

    I will say that right now I'm eating 2700 calories and not gaining and sometimes I am hungry at the end of the day. I guess that alone could mean I am burning more than I think? I'm aiming for 1lb/wk so I was going to up cals from 2700 to 3400.

    That is a huge jump in cals. I suggest you try adding 100 cals per day and see what the results are. Are you trying to maintain, lose, or gain? See if you see a difference.

    You are very active are you hungry or just bored? Sounds like you ROCK your days. :)

    Wanting to lose 20-30 lbs. zumba is for fun, i lift for strength and physique, and walk so I'm not just sitting all day at work. My goal has been 2700 but for the past few days I've been eating 3000-3100 due to hunger.

    For reference zumba is about 50-60min/session. Lifting is 20-45 mins depending on body part worked.
  • shadow2soul
    shadow2soul Posts: 7,692 Member
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    aliciab307 wrote: »
    shadow2soul wrote: »
    The best way to figure out it's accuracy for you is to follow it for a couple weeks (4-6) and see if your weight loss matches what is expected for your average intake/burn (fitbit displays 30 day averages on your profile page).

    For example:
    30 Day average Burn from Fitbit Surge - 2483
    30 Day average intake - 2006
    30 Day average deficit - 477
    477*30= 14310
    14310/3500 = 4.088...
    Weight lost = 4.7

    So for the past 30 days, mine hasn't been 100% accurate, but so far it isn't overestimating either.

    Thanks. I'm going to start that today. Just afraid of eating 3400 cals! Do you wear yours on dominant or nondominant? I've been wearing mine on non dominant but trying out dominant today. Wondering how different the numbers will be for each arm.

    I have been alternating here lately. After 2 weeks of wearing it on my non-dominate hand I ended up with a rash under the rubber part of the band, but I think I might have been wearing it too tight. Now I only tighten it during exercise and I wash the band after I workout. I'm alternating weekly now. So far it doesn't seem to make a difference on calorie burns/step counts or anything like that. If it is effecting them, it's not a big enough difference for me to notice.
  • aliciab307
    aliciab307 Posts: 370 Member
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    shadow2soul wrote: »

    I have been alternating here lately. After 2 weeks of wearing it on my non-dominate hand I ended up with a rash under the rubber part of the band, but I think I might have been wearing it too tight. Now I only tighten it during exercise and I wash the band after I workout. I'm alternating weekly now. So far it doesn't seem to make a difference on calorie burns/step counts or anything like that. If it is effecting them, it's not a big enough difference for me to notice.

    Thats great to know. So far step count has been fine. Thanks
  • kuranda10
    kuranda10 Posts: 593 Member
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    I just "tested" my Charge HR using the formula above and it's not bad.

    If anything it's slightly underestimating, which is OK for me.
  • editorgrrl
    editorgrrl Posts: 7,060 Member
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    The only way to gauge the accuracy of your Fitbit is to trust it for several weeks then reevaluate your results.

    I have a Fitbit Flex & log exercise in Fitbit—never MFP. I eat back all my adjustments, lost the weight, and have maintained for 8 months. So my Fitbit burn is my TDEE (total daily energy expenditure).

    It will take trial & error to find what works for you.
  • heybales
    heybales Posts: 18,842 Member
    edited March 2015
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    Lifting is going to be an inflated calorie burn if calculated by HRM readings - totally wrong use of the formula.

    HRM formula is ONLY valid for steady-state aerobic, same HR for 2-4 min.

    If lifting correctly, it should be totally opposite of that state.

    Step based or HR based calorie burn devices should have lifting manually logged.

    Weights on Fitbit database, Strength Training on MFP database.

    With corrected numbers (you can correct past 2 weeks if you have decent estimate of time start and duration), how does the TDEE look now?

    Walking daily should be accurate, but you'd need to get a handle on if the steps seen accurate.
    If getting a lot of extra steps, then that's inflated too.
  • oludi
    oludi Posts: 15 Member
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    I love the individual workout stats
  • aliciab307
    aliciab307 Posts: 370 Member
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    As far as lifting, if inflated then my burn must be very low. range from 100-400 cals depending on length of workout. Some lifting sessions are more endurance based and HR increases like I'm doing cardio.

    So if I correct the numbers, how would I correct? Just add exercise as lifting and add time and let fitbit calculate burn?

    I checked and steps are accurate. Placed on dominant wrist to prevent extra steps.
  • heybales
    heybales Posts: 18,842 Member
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    aliciab307 wrote: »
    As far as lifting, if inflated then my burn must be very low. range from 100-400 cals depending on length of workout. Some lifting sessions are more endurance based and HR increases like I'm doing cardio.

    So if I correct the numbers, how would I correct? Just add exercise as lifting and add time and let fitbit calculate burn?

    I checked and steps are accurate. Placed on dominant wrist to prevent extra steps.

    Correct, compared to cardio it is low.
    Depending on how strong a workout, and amount of repair body does in next 24-36 hrs, you'll get increased calorie burn then, but that is even harder to determine. Free fat loss deficit really.

    Weights is sets and rep ranges 4-15, rests of 2-4 min.
    Circuit training is rep ranges over 15, rests up to 1 min, multiple circuits.
    Calisthenics is rep ranges over 20, minimal rests, usually body weight.

    The closer your workout is to the bottom there, the closer to a better estimate the HR formula can give, since as you've observed, cardio-like HR increase and long duration.
  • 3JinItaly
    3JinItaly Posts: 27 Member
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    Hi everyone! So from what I'm reading, I am to only enter my activity into the fitbit and food into mfp. Correct? The amount of calories that my fitbit is telling me to eat is a LOT extra and it seems like too much!

    I lost 22lbs. pretty quickly by using mfp and starting to exercise regularly, but now I have been plateaued for almost 9 weeks! I have tried every combination that I know to try and nothing is working!

    I am a short 5'4" and weight 151lbs. I live in Italy, so I walk everywhere and on a slow day, clock in at minimum 12,000 steps. Some days upwards of 15,000. I also do the Jamie Eason strength trainer program of weightlifting 4 days a week and a kickboxing class 6 days a week. So, yes, I'm working out/moving a lot. There is such conflicting information though about should you eat back calories, should you set your activity level lower, etc. and I literally don't know what the right combination is. I've been eating around 1600 calories more or less and now I'm starting to think that perhaps its not enough. Some websites say that starvation mode is just a myth while others say its a real thing, and I don't know what to believe.

    So, perhaps for the next week, I will trust my fitbit and eat back the calories that it tells me to, just to see what happens.

    Any thoughts about its accuracy??

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