How are calories burned from exercise calculated via iPhone step counts?

dkf295
dkf295 Posts: 3 Member
in Fitness and Exercise
After noticing a regular pattern of losing more weight than it seems I should have after days I exercise, I decided to compare the number of calories the app THINKS I burned by automatically populating steps from my iPhone, to a few calculators that take height, weight, age, gender, distance, and time into account.

For a set distance of walking, the app thought I burned 18 calories. All the calculators I used thought I burned 65.

Does anybody know how the calories burned through exercise are automatically populated? There’s got to be some reason for such a large disparity, and it really throws off calorie counting especially on days when I’m a lot more active.

Replies

  • yskaldir
    yskaldir Posts: 202 Member
    Is your activity level set to sedentary?
  • lorrpb
    lorrpb Posts: 11,463 Member
    I don't think MFP gives me any extra calories until I have at least 5000 steps. I'm set to sedentary.
  • AidenT94
    AidenT94 Posts: 39 Member
    Do you have negative calories enabled? When I set up my Fitbit, it had turned off negative calories for me and refused to calculate them.
  • dkf295
    dkf295 Posts: 3 Member
    My activity level was set to lightly active, I changed it to active and it looks like it adjusted the daily calorie goal upwards by about 200. I guess I’ll see what that does for steps -> calories burned. Didn’t really think about that, because why would the activity level change how many calories you’re burning via exercise versus steps, distance, and age/gender/height/weight?
  • NorthCascades
    NorthCascades Posts: 10,968 Member
    An active person moves more than a lightly active person and needs more calories as a result.
  • dkf295
    dkf295 Posts: 3 Member
    NorthCascades wrote: »
    An active person moves more than a lightly active person and needs more calories as a result.

    I got that part, I meant that someone suggested changing it to active to solve my issue - that being, that the rate the app is adding calories burned under exercise based on my pedometer is roughly 1/4 of what it should be. Also, adjusting your calorie goal based on activity level AND essentially subtracting calories based off of activity from pedometer data/manually added exercise is redundant. However, this does help me out in another way as I was seeking a way to adjust for my own metabolism which is a bit weird, which adjusting the activity level will (mostly) accomplish.

    Having just tried changing the activity level two active and then re—testing the rate at which calories are added, there appears to be no difference between the “lightly active” and “active” activity levels. So, my original problem is still there.
  • NorthCascades
    NorthCascades Posts: 10,968 Member
    I think it's a little bit more complicated than you're thinking.

    An active person walks more than a lightly active person. If you say you're "active," the system will expect more steps from you in a day than if you say you're "lightly active" or "sedentary." I don't know what the numbers are. But you don't get extra credit for the steps you're already expected to take - that would be double counting. You should be getting the same number of calories per mile, but more of them are part of the number you start the day with at higher activity levels.

    Walking calories per mile ~= your body weight in pounds / 3.
  • ryenday
    ryenday Posts: 1,540 Member
    I think there is something not right in the Apple Watch to MFP sync regarding steps. I am set to sedentary. 11,776 steps gives me 115 calories (significantly less, I’ve been told than a Fitbit would.) Btw, I’m 160 ish pounds.

    58w3nynlkd2b.jpeg

    It gets worse if I do any workout that syncs via the Apple Watch. If I record any workout the step calories go to zero ( or go negative if negative adjustments are enabled). Again, my activity level is set to sedentary so this should not be the way it works.

    0jaym2zjb9ah.jpeg
  • davidyaches
    davidyaches Posts: 7 Member
    Reviving this thread. I generally understand how the calculation works. The app is predicting your calorie burn based on your activity in real time. So if you do a big run, it will give you credit for a large amount of calories as it thinks you will be burning at that pace. If you then get in bed for the rest of the day, and have negative adj on, you will see the calories actually go down (I believe) as it has over calculated the burn.

    However, I don't understand the philosophy when it comes to separately tracked exercises. So lets say I walk 10k steps, it shows me I burned 250 calories. Now if I wake up, and do an exercise on my Apple Watch that shows I burned 400 calories (and I moved 5k steps), the app will record 400 calories and nothing for steps (correct behavior as all my steps are attributable to the morning exercise for which I am already getting credit. Now I then walk another 10K steps except the app only gives me credit for 100 calories. This is not the correct behavior. The 400 calories was calculated separately by the watch (using my heart rate, among other) so the app is not in the position to "over calculate) by calories. It should effectively be thinking I am at 0 and measure me like it did in the first example.

    Id be interested to understand why this is the case. Seems like wrong behavior.
  • neugebauer52
    neugebauer52 Posts: 1,120 Member
    I was wondering about this topic: After 1 year I had lost 30 kg, but according to MFP / exercise / gym machines I should have lost just over 37 kg during the same time. So either I didn't record my food / drinks accurately or I overestimated my work outs. Food and drinks intake I can check meal by meal, day by day. But exercise? When I started walking with 170 kg on my back, I was able to walk only short distances, very slowly and with small steps. Now, a year later I do walk somehow faster, cover bigger distances, but my steps? Ah yes indeed, they have increased in length! By about 25 cm a double step, which is an increase of about 18 %. I haven't come across a tracking device which is that clever to change suchlike improvements and calculate the changes in calories burned. Oh well, I have decided not to worry too much about that - I just trust MFP and its calculations, prepare my daily meal plan and exercise as much as possible. Thank you all members for invigorating thoughts, I always learn something new!
  • heybales
    heybales Posts: 18,842 Member
    davidyaches wrote: »
    Reviving this thread. I generally understand how the calculation works. The app is predicting your calorie burn based on your activity in real time. So if you do a big run, it will give you credit for a large amount of calories as it thinks you will be burning at that pace. If you then get in bed for the rest of the day, and have negative adj on, you will see the calories actually go down (I believe) as it has over calculated the burn.

    However, I don't understand the philosophy when it comes to separately tracked exercises. So lets say I walk 10k steps, it shows me I burned 250 calories. Now if I wake up, and do an exercise on my Apple Watch that shows I burned 400 calories (and I moved 5k steps), the app will record 400 calories and nothing for steps (correct behavior as all my steps are attributable to the morning exercise for which I am already getting credit. Now I then walk another 10K steps except the app only gives me credit for 100 calories. This is not the correct behavior. The 400 calories was calculated separately by the watch (using my heart rate, among other) so the app is not in the position to "over calculate) by calories. It should effectively be thinking I am at 0 and measure me like it did in the first example.

    Id be interested to understand why this is the case. Seems like wrong behavior.

    To you first point about big run, rest of the day thought to burn at same rate - no.

    For trackers that work correctly with MFP (Apple does not - unsync it directly) - MFP takes the daily burn given by device up ta time stamp, and figures rest of the day at MFP selected Activity Level, and from that total and burned so far creates an adjustment.

    Read the 2nd section here for how the math works out for all trackers that do it correctly, even though this is written from Fitbit perspective.

    http://community.myfitnesspal.com/en/discussion/10098937/faq-syncing-logging-food-exercise-calorie-adjustments-activity-levels-accuracy

    Your 2nd paragraph is seeing exactly why direct sync with Apple fails to allow MFP do correct math.
    Pacer app can sync with Apple Health, and then to MFP, and provide correct figures though.

    The tracker should always supply the TDEE up to that point, which if you have a workout it should obviously already be in the TDEE figure.

    If MFP is informed of a workout (synced in or manually entered) - it's assuming that a new TDEE from a tracker already includes those workout calories.
    Because of the math it's about to do with your eating goal - it backs that workout out from the daily burn so far.

    Tracker daily - MFP estimated - workout = adjustment.

    Base eating goal + workouts + adjustment = new eating goal.


    Here's the problem with direct Apple sync - Apple sends the workouts over correctly (that's optional).
    Apple sends a daily burn that is their estimate of Sedentary activity level over, it contains no workouts.
    Apple does NOT send the daily activity above that base burn.

    So the math MFP does makes it worse the more active you are, and the more workouts you do. Adjustment goes the wrong way.
  • heybales
    heybales Posts: 18,842 Member
    neugebauer52 wrote: »
    I was wondering about this topic: After 1 year I had lost 30 kg, but according to MFP / exercise / gym machines I should have lost just over 37 kg during the same time. So either I didn't record my food / drinks accurately or I overestimated my work outs. Food and drinks intake I can check meal by meal, day by day. But exercise? When I started walking with 170 kg on my back, I was able to walk only short distances, very slowly and with small steps. Now, a year later I do walk somehow faster, cover bigger distances, but my steps? Ah yes indeed, they have increased in length! By about 25 cm a double step, which is an increase of about 18 %. I haven't come across a tracking device which is that clever to change suchlike improvements and calculate the changes in calories burned. Oh well, I have decided not to worry too much about that - I just trust MFP and its calculations, prepare my daily meal plan and exercise as much as possible. Thank you all members for invigorating thoughts, I always learn something new!

    That stride length for those doing many steps (over 4K I'd suggest) is probably the biggest improvement to accuracy for daily burn.

    Because the devices are all basically measuring the impact of each step, and based on hang time and stride length setting, and expected impact based on weight, dynamically adjust that steps distance.

    Distance and time and weight = calories.

    So biggest improvement is getting the walking stride length correct for the pace done the vast majority of the day - not the grocery store shuffle, not the exercise pace - right in the middle. Then as the device dynamically adjusts up and down based on impact - it's starting at best place in the range.
    Improved distance accuracy - better calorie burn.

    And indeed, the default settings based on gender & height change based on weight easily.

    It's easy to walk a known distance at that seemingly slow pace and confirm distance seen is correct.

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