Does your Fitbit overestimate calories burned?

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daniip_la
daniip_la Posts: 678 Member
in Health and Weight Loss
I bought a Fitbit One a few weeks ago, and I'm really enjoying it. I'm goal-driven so I like to try to beat my numbers everyday since getting it. I've gone from almost no extra walking to 5 miles most days.

My worry is that it's grossly overestimating my calorie burn. I'm 26, F, 6', and 326lbs as of this morning. I've attached a screenshot of my Fitbit info from Wednesday.

I've lost a few pounds since getting the Fitbit, but I don't know if I could be losing more. I don't eat back all the calories MFP adjusts to give me. On Wednesday, for instance, I ate 2200 and MFP/Fitbit said I had 500 left. That's how most days go.

Anyone else experiencing this, or have any advice?

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Replies

  • macgurlnet
    macgurlnet Posts: 1,946 Member
    edited May 2016
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    Fitbit can overestimate for some and underestimate for others (I think my Flex underestimates). It's certainly possible the numbers are a bit off for you.

    My advice would be to log your food as accurately as you can for 4-6 weeks and eat back a portion (say, 50%) of the Fitbit calories earned. After 4-6 weeks, evaluate your weight loss and see if you need to eat more, eat less, or if you're losing as expected, stick with the 50%.

    ETA: Do you have MFP and Fitbit set for the same amount of weight loss per week?

    ~Lyssa
  • WBB55
    WBB55 Posts: 4,131 Member
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    Mine overestimates, so I changed my height down an inch to lower the BMR. It's pretty accurate now. But like macgurl said, you might want to first average out some trends over a few weeks and see if you're losing at the expected rate or not.
  • nettasaura
    nettasaura Posts: 173 Member
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    Mine underestimates by a little bit. I could raise my height to compensate, but I'm ok with losing a little faster than expected. ;)
  • ekat120
    ekat120 Posts: 407 Member
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    My One seems to be right on, or underestimating very slightly. Your burn does seem high at first glance, but I'm 5'7" and 140 lbs, and mine gives me about 1,950 Cals for a day when I walk about 10,000 steps. At your height and weight, I wouldn't be surprised if you really do burn that much.

    I agree with the above that you just have to track and see what happens. When I got my first Fitbit (a Flex), I thought there was no way I was burning what it said I was. But I ate what it said and tracked, and realized it was actually pretty accurate.

    I don't think it affects the numbers, but I don't think you need to track your walks separately (the 2 mi walk in the activity section).

    Awesome job on the extra walking!
  • Chellellelle
    Chellellelle Posts: 595 Member
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    I thought my Charge HR was overestimating until I actually looked up my BMR and my caloric needs based on my activity levels and realized it was pretty accurate.

    I inputed your numbers (assuming you are 5 foot 6) in this formula to find your BMR, which is the calories you would burn at your height, weight and age if you stayed in bed all day and didn't move. http://www.bmi-calculator.net/bmr-calculator/#result

    BMR = 2261.1

    I then used Harris Benedict Equation to multiply times your activity level to find the calories you would need while being active.
    http://www.bmi-calculator.net/bmr-calculator/harris-benedict-equation/

    Activity Calories
    = 3109 (light activity)
    = 3504 (moderate activity)
    = 3900 (very active)

    So your Fitbit may be off just a hair, but not by a lot judging by those numbers.
  • daniip_la
    daniip_la Posts: 678 Member
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    ekat120 wrote: »
    My One seems to be right on, or underestimating very slightly. Your burn does seem high at first glance, but I'm 5'7" and 140 lbs, and mine gives me about 1,950 Cals for a day when I walk about 10,000 steps. At your height and weight, I wouldn't be surprised if you really do burn that much.

    I agree with the above that you just have to track and see what happens. When I got my first Fitbit (a Flex), I thought there was no way I was burning what it said I was. But I ate what it said and tracked, and realized it was actually pretty accurate.

    I don't think it affects the numbers, but I don't think you need to track your walks separately (the 2 mi walk in the activity section).

    Awesome job on the extra walking!

    I track my walks separately because I do them separately. I walk 2 or 3 miles at a time, twice a day, and use the tracking function instead of logging them.
  • daniip_la
    daniip_la Posts: 678 Member
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    Chellellelle wrote: »
    I thought my Charge HR was overestimating until I actually looked up my BMR and my caloric needs based on my activity levels and realized it was pretty accurate.

    I inputed your numbers (assuming you are 5 foot 6) in this formula to find your BMR, which is the calories you would burn at your height, weight and age if you stayed in bed all day and didn't move. http://www.bmi-calculator.net/bmr-calculator/#result

    BMR = 2261.1

    I then used Harris Benedict Equation to multiply times your activity level to find the calories you would need while being active.
    http://www.bmi-calculator.net/bmr-calculator/harris-benedict-equation/

    Activity Calories
    = 3109 (light activity)
    = 3504 (moderate activity)
    = 3900 (very active)

    So your Fitbit may be off just a hair, but not by a lot judging by those numbers.

    Thanks for working the math, I'm actually 6' even so that raises it a bit. I know by calculating my BMR/TDEE the numbers aren't far off from what the Fitbit says, I just don't think I can lose by eating that much. I'm used to eating around 1700 with no exercise, and I can't imagine walking adds that much.
  • shadow2soul
    shadow2soul Posts: 7,692 Member
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    The zip and flex underestimated for me by about an avg 200 calories per day. Blaze and Surge seem to be accurate for me.

    Considering your weight and height it might not be that far off at all.
  • daniip_la
    daniip_la Posts: 678 Member
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    macgurlnet wrote: »
    Fitbit can overestimate for some and underestimate for others (I think my Flex underestimates). It's certainly possible the numbers are a bit off for you.

    My advice would be to log your food as accurately as you can for 4-6 weeks and eat back a portion (say, 50%) of the Fitbit calories earned. After 4-6 weeks, evaluate your weight loss and see if you need to eat more, eat less, or if you're losing as expected, stick with the 50%.

    ETA: Do you have MFP and Fitbit set for the same amount of weight loss per week?

    ~Lyssa

    Yes, I'm set for a 2lb/week loss on MFP and a 1,000cal/day deficit on Fitbit.

    I weigh all my food to the gram on a food scale, and double check calorie entries with the USDA website entry. I'm confident my logging is as accurate as possible.
  • omma_to_3
    omma_to_3 Posts: 3,265 Member
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    Mine underestimates a bit, but almost entirely because it thinks my BMR is lower than it really is (according to multiple tests at a hospital). For anything step based (running and walking) it seems very accurate to me, based on the BMR formulas. If you know your BMR is higher or lower than the estimates, it will be off.

    Now that said, I've seen studies that show the calorie calculation is way off on Fitbits. But I have definitely not found that to be the case.
  • ryry_
    ryry_ Posts: 4,966 Member
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    I found for me it defintely overestimated. It would give me 160 calories for a 15 minute leisurely walk and said it was very active minutes. If I manually logged a 3.0 mph walk on the site it would only give me like 65 calories.

    For some its accurate and for some its not. The only weigh to know is to track your real world results vs what it estimate and then compare.
  • Need2Exerc1se
    Need2Exerc1se Posts: 13,576 Member
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    I don't know if mine (Charge HR) is accurate or not but it doesn't seem far off based on what I think I'm eating and my loss rate.
  • knelson095
    knelson095 Posts: 254 Member
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    I feel mine is pretty accurate. I have the One and I clip it to my bra. I usually eat what it sends over to mfp, at least when I can get them to talk to each other properly...but that is a whole different issue.
  • Need2Exerc1se
    Need2Exerc1se Posts: 13,576 Member
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    ryry62685 wrote: »
    I found for me it defintely overestimated. It would give me 160 calories for a 15 minute leisurely walk and said it was very active minutes. If I manually logged a 3.0 mph walk on the site it would only give me like 65 calories.

    For some its accurate and for some its not. The only weigh to know is to track your real world results vs what it estimate and then compare.

    Doesn't Fitbit measures total calories not additional calories? On a 15 min leisurely walk you very well may burn 160 calories if BMR is included.
  • zyxst
    zyxst Posts: 9,134 Member
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    Need2Exerc1se wrote: »
    ryry62685 wrote: »
    I found for me it defintely overestimated. It would give me 160 calories for a 15 minute leisurely walk and said it was very active minutes. If I manually logged a 3.0 mph walk on the site it would only give me like 65 calories.

    For some its accurate and for some its not. The only weigh to know is to track your real world results vs what it estimate and then compare.

    Doesn't Fitbit measures total calories not additional calories? On a 15 min leisurely walk you very well may burn 160 calories if BMR is included.

    Fitbit burns include BMR.

    I find my old Ultra and new One accurate. The Zip is very inaccurate for me and I'm sure I got a dodgy Zip.
  • RoxieDawn
    RoxieDawn Posts: 15,488 Member
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    My charge overestimated calorie burns and steps. But I never calibrated the walking or running strides like i have my garmin.
  • macgurlnet
    macgurlnet Posts: 1,946 Member
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    daniip_la wrote: »
    macgurlnet wrote: »
    Fitbit can overestimate for some and underestimate for others (I think my Flex underestimates). It's certainly possible the numbers are a bit off for you.

    My advice would be to log your food as accurately as you can for 4-6 weeks and eat back a portion (say, 50%) of the Fitbit calories earned. After 4-6 weeks, evaluate your weight loss and see if you need to eat more, eat less, or if you're losing as expected, stick with the 50%.

    ETA: Do you have MFP and Fitbit set for the same amount of weight loss per week?

    ~Lyssa

    Yes, I'm set for a 2lb/week loss on MFP and a 1,000cal/day deficit on Fitbit.

    I weigh all my food to the gram on a food scale, and double check calorie entries with the USDA website entry. I'm confident my logging is as accurate as possible.

    Okay - that's awesome!

    I still think you'll be best off logging calories in as accurately as possible - which you are - give it 4-6 weeks and evaluate your weight loss at that point. Then you'll have a pretty good idea of how accurate your Fitbit's numbers are.

    ~Lyssa
  • glassyo
    glassyo Posts: 7,592 Member
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    What Lyssa said. :)

    My charge HR SERIOUSLY overestimated my exercise calorie burn. Trying to figure that out helped me to figure out my One was overestimating too. The first ever fitbit was awesome tho. :)

    My One is being nicer to me lately tho.

    But with your stats, you very easily are burning what it says you're burning.
  • daniip_la
    daniip_la Posts: 678 Member
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    Thanks everyone for your input! Seems general consensus is to just wait it out and see, which is what I'll do.
  • Colorscheme
    Colorscheme Posts: 1,179 Member
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    How do you guys know if your fitbit is overestimeating or underestimating? my fitbit says my tdee is about 2100 cals a day and that sounds about right given I'm 5'7" and 158 lbs.

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