Accurately measuring calories burned

onemanpeloton
onemanpeloton Posts: 58 Member
edited November 27 in Fitness and Exercise
Can anyone recommend the most reliable (publicly accessible) way of measuring calories burned?

I cycle, and use a power meter and hrm but I still read a lot that strava doesn't given a good indication of calories burned, and tends to overshoot.

This is quite problematic if you got to great lengths to weigh all your food in an effort to lose weight.

Replies

  • Machka9
    Machka9 Posts: 25,687 Member
    edited July 2018
    The power metre is supposed to do it.

    But I use an estimate and it isn't problematic at all ... if I lose weight, I've got it right. :)


    BTW - my own personal estimate is 100 calories for every 5 km.

    Co-incidentally, that matches Strava quite well. :)

  • onemanpeloton
    onemanpeloton Posts: 58 Member
    Machka9 wrote: »
    The power metre is supposed to do it.

    But I use an estimate and it isn't problematic at all ... if I lose weight, I've got it right. :)


    BTW - my own personal estimate is 100 calories for every 5 km.

    Co-incidentally, that matches Strava quite well. :)

    Very true, I guess the scales will tell the story!

    Interesting, how did you calculate that? My own calculations may be difficult due to the varied elevation of my rides. Some miles are hilly and some are flat. I imagine this is partly where a lot of strava's variability comes in to it
  • Djproulx
    Djproulx Posts: 3,084 Member
    I have a power meter on the bike and believe that is as accurate a method as any, since it is measuring actual work. My Vector3 measurements are uploaded to Garmin Connect and Training Peaks. I just accept those numbers. My running calorie expenditure is derived from a chest strap mounted HRM and uploaded in the same manner.

    I do not use Strava.
  • kcjchang
    kcjchang Posts: 709 Member
    edited July 2018
    Convert total kj from your ride to kcal and divid by your metabolic efficiency (determine at a lab). 25% is generally used and don't know if any application allow you to set the efficiency. PM is best tool you can have in determining your total work out side of a lab. Dump the HRM.
  • Machka9
    Machka9 Posts: 25,687 Member
    onemanpeloton wrote: »
    Machka9 wrote: »
    The power metre is supposed to do it.

    But I use an estimate and it isn't problematic at all ... if I lose weight, I've got it right. :)


    BTW - my own personal estimate is 100 calories for every 5 km.

    Co-incidentally, that matches Strava quite well. :)

    Very true, I guess the scales will tell the story!

    Interesting, how did you calculate that? My own calculations may be difficult due to the varied elevation of my rides. Some miles are hilly and some are flat. I imagine this is partly where a lot of strava's variability comes in to it

    Yeah, some of my kilometres are hilly and some are flat too.


    Now, as I lost weight, I found that 90 calories for every 5 km was probably slightly more accurate, based on the way my weight loss slowed a bit.
  • BrianSharpe
    BrianSharpe Posts: 9,248 Member
    I've found Strava to estimate far more calories than my Garmin when running but with my power meter the biking lines up with Garmin Connect so it should be pretty close.
  • rsclause
    rsclause Posts: 3,103 Member
    I always consider calories burned as a guesstimate rather than the gospel. Of course I am not really training but in this for general fitness and quality of life.
  • aokoye
    aokoye Posts: 3,495 Member
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").
  • NorthCascades
    NorthCascades Posts: 10,968 Member
    Your power meter. Total KJ. This will have a maximum error of 5%, and puts you in the middle of that range.
  • onemanpeloton
    onemanpeloton Posts: 58 Member
    aokoye wrote: »
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").

    Thanks. I see this alot. "Strava doesnt agree with Garmin so Strava is wrong". How do we know that Garmin is right?
  • onemanpeloton
    onemanpeloton Posts: 58 Member
    NorthCascades wrote: »
    Your power meter. Total KJ. This will have a maximum error of 5%, and puts you in the middle of that range.

    How is total KJ calculated though? If we assume that the power data is accurate then is there still not an algorithm applied to that data to calculate KJ?
  • NorthCascades
    NorthCascades Posts: 10,968 Member
    1 watt = 1 joule per second.

    200 watts for 60 minutes = 7,200,000 joules, or 720 kJ. Because 60 minutes is 3,600 seconds.
  • aokoye
    aokoye Posts: 3,495 Member
    onemanpeloton wrote: »
    aokoye wrote: »
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").

    Thanks. I see this alot. "Strava doesnt agree with Garmin so Strava is wrong". How do we know that Garmin is right?

    Here are some links for you including one that is oft cited, one from Training Peaks, and another from TrainerRoad.
  • scorpio516
    scorpio516 Posts: 955 Member
    And 1 J = 2.39x10^-4 KCal.

    And the human body is about 22% efficient (18-26% in cycling and rowing). i.e. for every 100 KCal burned, 22 KCal is motive power and 78 KCal is heat.

    So, to turn this all around: My FTP is a measly 150 W. 60 minutes @ FTP will be 540,000 J / 540 KJ. That's 129 kcal in motive force. Applying 22% efficiency, that's 586 KCal burned by my engine for an hour @ FTP. Although it could be anywhere from 715 kcal to 500 kcal depending on my personal efficiency that day.
  • Machka9
    Machka9 Posts: 25,687 Member
    edited July 2018
    onemanpeloton wrote: »
    aokoye wrote: »
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").

    Thanks. I see this alot. "Strava doesnt agree with Garmin so Strava is wrong". How do we know that Garmin is right?

    From what I've observed, I've never known Garmin to be right. It usually produces numbers much higher than what they should be. Just what I've noticed.

    Strava seems to be a lot more accurate ... lower!


    Which one is closest to your power metre?
  • aokoye
    aokoye Posts: 3,495 Member
    Machka9 wrote: »
    onemanpeloton wrote: »
    aokoye wrote: »
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").

    Thanks. I see this alot. "Strava doesnt agree with Garmin so Strava is wrong". How do we know that Garmin is right?

    From what I've observed, I've never known Garmin to be right. It usually produces numbers much higher than what they should be. Just what I've noticed.

    Strava seems to be a lot more accurate ... lower!


    Which one is closest to your power metre?

    The bit that I quoted doesn't make any sense. All a power meter is doing is transmitting the current power output. It is not calculating how many calories you're burning, your average watts, or any other number. That is akin to the idea that a heart rate strap will tell you how many calories you've burned or do anything other than transmitting data to device with a visual display that then tells you what your HR is at the moment (and may have the ability to estimate calories burned).

    When people say, "Garmin is accurate in calculating calories burned with a power meter" what they're saying is that the equation that Garmin uses appears to be accurate. As in, your Garmin Edge or Forerunner has been fed these numbers over the course of the ride and is spitting out what appears to be an accurate calorie calculation.
  • scorpio516
    scorpio516 Posts: 955 Member
    aokoye wrote: »
    Machka9 wrote: »
    onemanpeloton wrote: »
    aokoye wrote: »
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").

    Thanks. I see this alot. "Strava doesnt agree with Garmin so Strava is wrong". How do we know that Garmin is right?

    From what I've observed, I've never known Garmin to be right. It usually produces numbers much higher than what they should be. Just what I've noticed.

    Strava seems to be a lot more accurate ... lower!


    Which one is closest to your power metre?

    The bit that I quoted doesn't make any sense. All a power meter is doing is transmitting the current power output. It is not calculating how many calories you're burning, your average watts, or any other number. That is akin to the idea that a heart rate strap will tell you how many calories you've burned or do anything other than transmitting data to device with a visual display that then tells you what your HR is at the moment (and may have the ability to estimate calories burned).

    When people say, "Garmin is accurate in calculating calories burned with a power meter" what they're saying is that the equation that Garmin uses appears to be accurate. As in, your Garmin Edge or Forerunner has been fed these numbers over the course of the ride and is spitting out what appears to be an accurate calorie calculation.

    From above:. 1 Watt = 1 Joule per second. A Joule is the SI unit of work. So are BTU and calories. 1000 Joules are equal to 0.239 kilocalories. So a power meter is transmitting work. It's just that the agreed upon unit is the Watt, not the calorie or kcal or Calorie.
  • kcjchang
    kcjchang Posts: 709 Member
    aokoye wrote: »
    The bit that I quoted doesn't make any sense. All a power meter is doing is transmitting the current power output. It is not calculating how many calories you're burning, your average watts, or any other number.
    It is measuring work done (energy expended) in Joule per second.
    aokoye wrote: »
    That is akin to the idea that a heart rate strap will tell you how many calories you've burned or do anything other than transmitting data to device with a visual display that then tells you what your HR is at the moment (and may have the ability to estimate calories burned).
    No, a heart rate monitor just tells you how many beats per second your heart is moving. It does not directly relate to energy expenditure. Give yourself a good scare or drink a pot of coffee, did you just burn more energy? A bit, but negligible.
    aokoye wrote: »
    When people say, "Garmin is accurate in calculating calories burned with a power meter" what they're saying is that the equation that Garmin uses appears to be accurate. As in, your Garmin Edge or Forerunner has been fed these numbers over the course of the ride and is spitting out what appears to be an accurate calorie calculation.
    Yes and no. Direct work measured is very accurate. Translating that to how much energy you actually expended is somewhat a black box because there isn't a customized adjustment for gross efficiency. However, it is far more accurate than estimate derived from a HRM. Those estimates are based on a very small number of studies. Direct measurement is always going to be better than inferences.
  • aokoye
    aokoye Posts: 3,495 Member
    scorpio516 wrote: »
    aokoye wrote: »
    Machka9 wrote: »
    onemanpeloton wrote: »
    aokoye wrote: »
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").

    Thanks. I see this alot. "Strava doesnt agree with Garmin so Strava is wrong". How do we know that Garmin is right?

    From what I've observed, I've never known Garmin to be right. It usually produces numbers much higher than what they should be. Just what I've noticed.

    Strava seems to be a lot more accurate ... lower!


    Which one is closest to your power metre?

    The bit that I quoted doesn't make any sense. All a power meter is doing is transmitting the current power output. It is not calculating how many calories you're burning, your average watts, or any other number. That is akin to the idea that a heart rate strap will tell you how many calories you've burned or do anything other than transmitting data to device with a visual display that then tells you what your HR is at the moment (and may have the ability to estimate calories burned).

    When people say, "Garmin is accurate in calculating calories burned with a power meter" what they're saying is that the equation that Garmin uses appears to be accurate. As in, your Garmin Edge or Forerunner has been fed these numbers over the course of the ride and is spitting out what appears to be an accurate calorie calculation.

    From above:. 1 Watt = 1 Joule per second. A Joule is the SI unit of work. So are BTU and calories. 1000 Joules are equal to 0.239 kilocalories. So a power meter is transmitting work. It's just that the agreed upon unit is the Watt, not the calorie or kcal or Calorie.

    You misunderstood what I was saying (or perhaps I said it wrong, or both). What I was saying is that a power meter isn't feeding your head unit the number of calories you've burned. If it did then the watt bike wouldn't also have the apparent issue of an accurate amount of watts being displayed but a arguably inaccurate number of calories.
  • aokoye
    aokoye Posts: 3,495 Member
    kcjchang wrote: »
    aokoye wrote: »
    The bit that I quoted doesn't make any sense. All a power meter is doing is transmitting the current power output. It is not calculating how many calories you're burning, your average watts, or any other number.
    It is measuring work done (energy expended) in Joule per second.
    aokoye wrote: »
    That is akin to the idea that a heart rate strap will tell you how many calories you've burned or do anything other than transmitting data to device with a visual display that then tells you what your HR is at the moment (and may have the ability to estimate calories burned).
    No, a heart rate monitor just tells you how many beats per second your heart is moving. It does not directly relate to energy expenditure. Give yourself a good scare or drink a pot of coffee, did you just burn more energy? A bit, but negligible.
    aokoye wrote: »
    When people say, "Garmin is accurate in calculating calories burned with a power meter" what they're saying is that the equation that Garmin uses appears to be accurate. As in, your Garmin Edge or Forerunner has been fed these numbers over the course of the ride and is spitting out what appears to be an accurate calorie calculation.
    Yes and no. Direct work measured is very accurate. Translating that to how much energy you actually expended is somewhat a black box because there isn't a customized adjustment for gross efficiency. However, it is far more accurate than estimate derived from a HRM. Those estimates are based on a very small number of studies. Direct measurement is always going to be better than inferences.

    See the above. We're not actually disagreeing about anything here.
  • sijomial
    sijomial Posts: 19,809 Member
    aokoye wrote: »
    scorpio516 wrote: »
    aokoye wrote: »
    Machka9 wrote: »
    onemanpeloton wrote: »
    aokoye wrote: »
    I'll echo most people by saying that my Garmin appears to accurately tell me the calories burned when given the data from my power meter (your HRM is useless in this regard). The issue with Strava is that whatever equation they're using, it doesn't seem to be accurate.

    Unfortunately you can't edit an entry in Strava to update the calories. Basically what I do is have Garmin Connect sync with Training Peaks, Strava, and MFP. Training Peaks doesn't manipulate the data the way that Strava does so it will show me the same number of calories that Garmin does. It, however, isn't public facing in the way Strava is (I'm assuming that's what you meant by "publicly accessible").

    Thanks. I see this alot. "Strava doesnt agree with Garmin so Strava is wrong". How do we know that Garmin is right?

    From what I've observed, I've never known Garmin to be right. It usually produces numbers much higher than what they should be. Just what I've noticed.

    Strava seems to be a lot more accurate ... lower!


    Which one is closest to your power metre?

    The bit that I quoted doesn't make any sense. All a power meter is doing is transmitting the current power output. It is not calculating how many calories you're burning, your average watts, or any other number. That is akin to the idea that a heart rate strap will tell you how many calories you've burned or do anything other than transmitting data to device with a visual display that then tells you what your HR is at the moment (and may have the ability to estimate calories burned).

    When people say, "Garmin is accurate in calculating calories burned with a power meter" what they're saying is that the equation that Garmin uses appears to be accurate. As in, your Garmin Edge or Forerunner has been fed these numbers over the course of the ride and is spitting out what appears to be an accurate calorie calculation.

    From above:. 1 Watt = 1 Joule per second. A Joule is the SI unit of work. So are BTU and calories. 1000 Joules are equal to 0.239 kilocalories. So a power meter is transmitting work. It's just that the agreed upon unit is the Watt, not the calorie or kcal or Calorie.

    You misunderstood what I was saying (or perhaps I said it wrong, or both). What I was saying is that a power meter isn't feeding your head unit the number of calories you've burned. If it did then the watt bike wouldn't also have the apparent issue of an accurate amount of watts being displayed but a arguably inaccurate number of calories.

    @aokoye

    I use a Wattbike and although it measures power accurately it also uses a totally bizarre algorithm to convert power to calories. Even their own helpdesk couldn't justify why they don't use the more usual formula (energy (kcal) = avg power (W) X duration (hours) X 3.6) to give net calories.
    My cynical suspicion is that the marketing department influenced that decision - "use our machine - burn more calories!".

    Strava seems to use yet another algorithm. Possibly the Strava algorithm is trying to estimate gross cals as the difference seems close to my estimated hourly RMR.

    When I feed my Wattbike workout data through Garmin and then on to my linked Strava account ONLY the Garmin numbers give what I would consider the true net calorie estimate.


    Example using a one hour FTP test at 213w (which should be a calculated 766.8 cal)
    • Wattbike gave me 953cal
    • Garmin used the same power data and gave me 769cal
    • Strava gave 857cal


    BTW - I don't use a power meter outdoors and Strava's attempt to estimate power from speed/distance/terrain works pretty well for me, maybe because I have awful aero the inflated gross estimates seem very reasonable for my net calories.
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