Accuracy of Fitbit calories burned

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Replies

  • scolaris
    scolaris Posts: 2,145 Member
    edited February 2016
    This has been really helpful!
    @PAV8888 thank you for all that analysis
    @Christine_72 too soon to tell, but I think it's believable. I'm really trying to streamline things. If I burn 1200 calories by noon according to the HR, I know I'll burn 2400 or better by midnight and then I can just relax and plan to eat 1800-2000 calories. Simple! But I don't want deficits that are too big, either, so then whenever I go over 2500 I have to decide if I'm going to eat a little more. Ugh... decisions... Still working it out.
  • PAV8888
    PAV8888 Posts: 14,260 Member
    People who enable negative adjustments are sometimes confused by the calories they "lose" by going to bed early, or by watching TV before midnight.

    This is an artefact of the way MFP calculates the Fitbit adjustment.

    The MAXIMUM number of calories you MIGHT lose to midnight can be predicted as follows:
    MAX_CAL_LOST = BMR / 1440 * M * F

    where:
    BMR = BMR as calculated here: http://www.myfitnesspal.com/tools/bmr-calculator
    M = Number of minutes you will be less active than your MFP activity setting between time of sync and midnight.
    F = factor calculated as:
    0.25 if you are setup as Sedentary in MFP
    0.4 if you are setup as Lightly Active in MFP
    0.6 if you are setup as Active in MFP
    0.8 if you are setup as Very Active in MFP
  • scolaris
    scolaris Posts: 2,145 Member
    Thanks!
  • Sonyavdg
    Sonyavdg Posts: 17 Member
    I have the charge (not HR) and it seems to be very accurate. As of this morning, my deficit as calculated by trendweight (based on actual weight lost) and my 30 day average deficit based on Fitbit calories burned and MFP logging for calories eaten are within 20 calories a day of each other.
  • Maxematics
    Maxematics Posts: 2,287 Member
    edited February 2016
    PAV8888 wrote: »
    People who enable negative adjustments are sometimes confused by the calories they "lose" by going to bed early, or by watching TV before midnight.

    This is an artefact of the way MFP calculates the Fitbit adjustment.

    The MAXIMUM number of calories you MIGHT lose to midnight can be predicted as follows:
    MAX_CAL_LOST = BMR / 1440 * M * F

    where:
    BMR = BMR as calculated here: http://www.myfitnesspal.com/tools/bmr-calculator
    M = Number of minutes you will be less active than your MFP activity setting between time of sync and midnight.
    F = factor calculated as:
    0.25 if you are setup as Sedentary in MFP
    0.4 if you are setup as Lightly Active in MFP
    0.6 if you are setup as Active in MFP
    0.8 if you are setup as Very Active in MFP

    I have negative adjustments enabled and don't lose any calories except for the morning. The best way to utilize Fitbit/MFP, in my opinion, is by changing your food plan from personalized to sedentary and keeping yourself sedentary on MFP as well. With sedentary you start low and earn calories throughout the day, but with personalized Fitbit tries to predict what you'll burn before you actually do. That constant calorie shift can be frustrating for people.

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