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Why The Huge Discrepancy?

wolf39us
wolf39us Posts: 163 Member
edited November 18 in Social Groups
I wanted to show a couple of photos from yesterday's workout on the elliptical complete with my brand new fitbit surge.




17634254522_e9beb5034b_z.jpgUntitled by Chris, on Flickr

17014132984_13faf6698d_z.jpgUntitled by Chris, on Flickr




As you can see there's a massive difference in calorie burn! I am proud to report that the HR monitor on the fitbit was within 1-3 bpm of the machine almost the entire way! But why such a large discrepancy?

The only thing I can think of is the fact that the fitbit has my height and gender and weight, whereas the machine only has my weight.

Replies

  • editorgrrl
    editorgrrl Posts: 7,060 Member
    Just as no two scales are ever calibrated exactly the same, a piece of equipment, MFP + Fitbit will give you three different burns. Trust your Fitbit for several weeks, then reevaluate your progress.
  • wolf39us
    wolf39us Posts: 163 Member
    I asked at the fitbit support and they said that the burn here also takes into account BMR + Height + Gender. So it makes sense I guess!
  • editorgrrl
    editorgrrl Posts: 7,060 Member
    Your Fitbit burn is TDEE (total daily energy expenditure), aka your maintenance calories. If you eat at a reasonable deficit from that, you will lose weight.
  • editorgrrl
    editorgrrl Posts: 7,060 Member
    Your Fitbit burn is TDEE (total daily energy expenditure), aka your maintenance calories. If you eat at a reasonable deficit from that, you will lose weight.
  • NancyN795
    NancyN795 Posts: 1,134 Member
    Since you should have your average heart rate and workout duration, plug the numbers into an online calculator and see which it agrees with. Here's one I found:

    http://www.shapesense.com/fitness-exercise/calculators/heart-rate-based-calorie-burn-calculator.aspx
  • heybales
    heybales Posts: 18,842 Member
    The elliptical machines have no good valid formula for calorie burn.
    No study has even shown a formula that would work with all the variables possible in the settings, and the differences in form doing them.

    So at the best they are probably taking what appeared to be your watts to get it moving, and used the average 23% efficiency turning energy in to mechanical motion.

    But that's assuming they got the watts right.

    But - You'd have to be very fit to burn 900 calories in a hour too.

    So that could be that you have a higher HRmax than Fitbit is assuming based on 220-age, and while Fitbit thought you were working out at say 100% of HRmax, you were actually at 80% - so not nearly the calorie burn it thinks.

    And HRmax has nothing to do with fitness level but genetics. Fitness just keeps it higher as you age.
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