FitBit calcluated calorie burn accuracy??

e_v_v
e_v_v Posts: 131 Member
in Fitness and Exercise
I have owned a FitBit for a couple years now and recently upgraded to the FitBit Ionic (released in October). I used my previous trackers primarily for counting steps and checking the time. With this newer version, I plan to use the automatic calculated calorie burn with my MFP app since the movement and heart rate sensors are improved and more accurate.

After using the tracker for a couple weeks, my calorie burn seems a bit high.

I am 5'3", 150 lbs., and have a generally muscular stature (ex-gymnast). Here's what my Ionic has calculated for my workouts lately:

Les Mills BODYPUMP class (1 hour): ~350 calories burned

I'm also a basketball coach, and I do practice with my girls as if I'm a player for a little extra exercise. Our practices are 90 minutes long and moderately difficult: ~650 calories burned

Does this seem high? Just right? I want something I can trust!!!

Replies

  • NorthCascades
    NorthCascades Posts: 10,968 Member
    Heart rate is a bad way to try to measure calories. There's some correlation between exercise intensity and heart rate but it's weak and noisy.
  • jjpptt2
    jjpptt2 Posts: 5,650 Member
    NorthCascades wrote: »
    Heart rate is a bad way to try to measure calories. There's some correlation between exercise intensity and heart rate but it's weak and noisy.

    While I agree as an absolute statement, I don't think that's very helpful for the op. Unreliable as HR and HRM-based calorie calculations may be, people still want/need a starting point. And it's not hard to sanity check calorie burns from HRMs.
  • jjpptt2
    jjpptt2 Posts: 5,650 Member
    edited December 2017
    OP, 350 cals for an hour long body pump class seems pretty reasonable.

    650 cals for an hour long at moderate effort seems a bit high to me, but not out of the realm of possibility.

    As a general rule, I'm skeptical of any calorie burn that is more than 10cals per minute. At a moderate intensity, I'd expect more like 7-8 cals per minute. If the workout is more interval-ish (periods of high effort mixed with periods of low effort), then I'd look closer to 5 cals per minute. A super high intensity effort can certainly push you over 10 cals per minute, but that's hard for most people to sustain for any length of time.

    Obviously there are a lot of assumptions and estimations involved with those numbers. But they are as good as anything and serve as easy sanity checks when you get calorie burns that differ from what you expect.

    Ultimately, as NorthCascades suggested, there's no good way to know for sure. Ultimately you'll have trust something as a starting point, then evaluate things as you go over the course of several weeks. If your expected results don't match your actual results, then you'll have to tweak something, then start the process over. If actual and expected are reasonably close, then you're on a good track and can be reasonably comfortable with your numbers.
  • NorthCascades
    NorthCascades Posts: 10,968 Member
    jjpptt2 wrote: »
    NorthCascades wrote: »
    Heart rate is a bad way to try to measure calories. There's some correlation between exercise intensity and heart rate but it's weak and noisy.

    While I agree as an absolute statement, I don't think that's very helpful for the op. Unreliable as HR and HRM-based calorie calculations may be, people still want/need a starting point. And it's not hard to sanity check calorie burns from HRMs.

    As far as usefulness to the OP, we would need to see Fitbit's code to have any idea how well it can account for basketball. We know using HR is dicey, and we know Fitbits are pedometers at heart.
  • evilpoptart63
    evilpoptart63 Posts: 397 Member
    I have recently realized my fitbit overestimates my calories. I weigh and log every bite of food that goes into my mouth and I was frustrated that my weight wasn't responding the way I expected it to. It's a good general estimate but it seems to be more accurate to compare your calories in and scale weight to the expected calories burned.
  • e_v_v
    e_v_v Posts: 131 Member
    Thanks for the feedback, guys!

    It's just frustrating in general that there's no way to calculate burned calories with 100% accuracy without using a kinesiology lab.

    When it comes to MFP, I have to eat back my exercise calories or else my energy and progress tanks. I wish there was something more reliable out there!
  • CarlydogsMom
    CarlydogsMom Posts: 645 Member
    Don't forget that these trackers include the calories burned whether or not you were exercising during that time frame (in other words, your BMI calories). For example, my BMI number is about 1450 (calories burned per day if I was lying in a coma doing nothing; body processes fueling themselves). Just so happens, that number is equivalent to about a calorie per minute.

    Example, this morning, I went on a low-intensity walk, 65 minutes total time. My tracker said I burned 220 calories. I'll subtract 65 calories that represent my BMI calories to get 155 calories total "net" exercise. To be honest, even that is probably a bit too high, but better...

    To go one step further, I know that walk is about 2.5 miles, which equates to 62 calories/mile (155/2.5), which in my mind makes sense. 88 calories/mile (220/2.5) as an exercise total seems high for me.

    So I generally subtract about a calorie per minute for my total workout time to get a better idea of true exercise burn.
  • fishgutzy
    fishgutzy Posts: 2,807 Member
    Generally speaking, an HRM won't accurately calculate cal burn unless it can be calibrated to you and your VO2 Max.
    There are many variables effect calorie burn. Using just HR it is likely just taking a mean from whatever database was use to create the algorithm.
    I use a Garmin Fenix 5X. But I do not synch it with MFP.
    I only log swimming. And then just enter 1min per lap. That is more conservative than the numbers from my Fenix. I use the Fenix to track distance and pace.
    I do not enter walking or steps. If I have a particularly vigorous spin class that tops 500 I might add it.
    Like any gadget, it has limits.
  • maybe1pe
    maybe1pe Posts: 529 Member
    I personally don't think those numbers are that far off. If you are truly moving a moderate difficulty for 90 minutes during basketball 650 is around 7 cals/min which isn't unreasonable, if you're actually working that hard.

    I've found mine to be very accurate and gets more and more accurate the longer I wear it.

    The only real way to find out is to experiment with what it tells you and see if you're still losing at the projected rate.

Categories