Fitbit gives higher calorie burn for steps taken throughout the day vs. intentional walking

swimmchick87
swimmchick87 Posts: 458 Member
in Fitness and Exercise
Does anyone else notice this? On days where I actually take longer, intentional exercise walks, fitbit gives me a WAY lower calorie burn than on the days where I just naturally get a lot of steps throughout my day, without doing any intentional walking for exercise.

I was working from home for a long time and if I didn't do any intentional walks, my steps could have easily been super low, like 1500 per day. I got to my 10,000 daily religiously, and almost all of that had to come from intentional walking. I also did more walking toward the evening hours as that's when I had time to do it. Based on the calorie burn fitbit gave me and the MFP adjustment, I'd often end up with about 100-150 added exercise calories per day.

This week I finally switched back to working in person. I get about 7500 steps just going about my day at work, and most days I haven't had to do any intentional walking to get up to 10K. I'm also getting many steps way earlier in the day than I did working from home. Fitbit is now saying my daily calorie burn is way higher, and I'm getting a 400-500 calorie adjustment from MFP.

I'm certainly not going to eat all that extra, but I'm just curious. Is this some sort of "glitch" or is there actual reasoning/research behind burning more calories walking throughout the day vs. taking an intentional walk? If anything, I would have assumed it would be the opposite- taking a long/intentional walk would burn more than just walking as you go about your day. Or is there something behind getting the steps earlier in the day vs. the evening?

Replies

  • autumnblade75
    autumnblade75 Posts: 1,661 Member
    I work 3rd shift, so I get ALL of my steps "early in the day" and then, while I'm sleeping, Fitbit steals them back away again.

    I got creative for a while and adjusted my time zone on MFP, to make any calories lost accrue to the next day. I have no problem starting with hardly anything and working harder to earn my extra snacks. I can't always go for a run later if Fitbit takes them back after I've eaten them...

    And then I gave up on that model entirely, rolled the workout calories into the calculation and am following the TDEE method. I had my doubts, but it's actually working better for me.

    But have you gone back and looked at completed days to see if any negative adjustments ever happened? Do you have negative adjustments enabled? Is the weight loss working smoothly?
  • heybales
    heybales Posts: 18,842 Member
    Fitbit is getting calorie burn from distance the steps take you, not just steps.

    So what to compare is the distance for the day, not the steps.

    Distance and time and mass is very accurate calorie burn calculations from decades of research using treadmills.

    It counts.

    But how your device is getting from steps to distance is based on stride length setting, and the impact of each step seen.
    It dynamically adjusts the distance for that step based on expected and seen impact.
    So if stride length is off, it may not be able to adjust accurately in 1 direction or another.

    One reason for the difference - all non-step time is given a burn rate of BMR, as if sleeping. Even if actually awake, sitting, moving arms, standing.
    So some constant moving through the day prevents that.
    Just a walk (which it may not be getting the distance correct for either) still allows vast amounts of non-step time.

    Again - this is why you compare distance not just steps.
  • swimmchick87
    swimmchick87 Posts: 458 Member
    edited January 2021
    There is barely any difference between the distance fitbit calculates for the days. Monday I had 4.08 miles, Tuesday 4.12, Wednesday 4.14. Last week, working from home, 4.03 Monday, 4.14 Tuesday, 4.16 Wednesday.

    I do have the negative adjustments enabled. Back when I was working in person all of the time, I noted that I had to get to about 7500 steps for the day in order for MFP to not deduct any calories, as I have mine set to "lightly active." That was motivating for me to never just have a "lazy day" even on the weekend, because I certainly wasn't going to have any of my calories taken away! I noticed that when I started working from home, I often had to get to around 9,000 or sometimes even more in order to avoid that negative adjustment.

  • heybales
    heybales Posts: 18,842 Member
    Here's the other potential reason for the difference, but I didn't mention it because normally it goes the other way - daily steps spread out have lower calories compared to same distance done in single walk.

    That effect is because Fitbit starts a workout when it see the HR go up with the steps and starts a workout, or you manually start it. But now Fitbit uses HR-based calorie burn, not distance based.
    For most people that formula using HR calorie burn is inflated at walking level of effort, it would be better if distance based was used.

    In theory it could go the other way, perhaps your HR is much lower than it expects for your stats compared to avg, and it gives less calories for the long walk it's making a workout of.
    Meds or being very fit could cause that underestimated burn.

    But, workouts should be showing up in your Fitbit exercise diary when it does that.
    Is that the case, workouts for the long walks?

    The difference in work/home steps and when you leave an activity level makes sense - but the distance should be different too.
    I'd imagine home steps being shorter unless you mean that's the same issue with distance being about the same, only calories being different.
    All based on Fitbit's reported daily burn. That's it.
  • swimmchick87
    swimmchick87 Posts: 458 Member
    edited January 2021
    It looks like fitbit is counting my intentional walks as "exercise." However, since my heart rate doesn't typically reach above 120 bpm on those, it's not counting "zone minutes." When I look back at this past week, I have very little "exercise" recorded by fitbit, yet the calorie burn is still much higher. I wonder if part of the super inflated calorie burn is perhaps just that stress=higher heart rate throughout the day (due to being back at work, it's much more challenging in person) and thus an inflated calorie burn.

    I will say, I had a non-heart rate tracking Alta for several years before this and I noticed very similar patterns, it's just the calorie burn wasn't so inflated. I noticed especially that if I got the majority of my steps in the late evening, fitbit never seemed to "catch up" the calories. Even though I'd still reach 10,000 steps that day, it would give me a lower calorie burn than on days when I got my steps earlier in the day. But the difference was maybe 100-200 calories, not 400-500 like it is now with the versa 3.

    The other thing that's different with the versa 3 is it counts floors, and my Alta didn't do that. I do tend to have about 10-12 "floors" on work days vs. 2-3 on most days I'm home. But even so, walking up 7-10 more flights of steps doesn't account for 500 extra calories.
  • heybales
    heybales Posts: 18,842 Member
    HR is not used for daily burn. Unless you have the steps and elevated HR long enough to allow it.

    Distance is.

    HR below a certain level, like 90 HR-flex for most - is invalid formula for calorie burn.
    Therefore unless steps and HR stay elevated for I believe 5 min (may have changed), Fitbit won't even auto-start a workout. During a workout is when it will start using HR-based formula for calorie burn.

    And to my point earlier - even when that formula is appropriate in the aerobic zone above 90, the lower end of that zone IS inflated using the formula.

    Floors aren't used in any calorie calcs - merely a display figure like steps or glasses of water. Because it can be highly inaccurate just using air pressure that weather can change.
    The HR zones don't change the formula used either.

    I can't imagine a scenario where the math would make a difference in calories for different parts of the day.

    Have you ever looked at your 24 hr graph, the 15 min increments - website on computer easiest to see.

    You can look at a range of minutes where you got the same steps early in day or later in day - same calories in a 15 min block no matter what.

    Now - doing walks later in the day for many people means they are not taking care of other active household things - those are being put off.
    So the exercise is not a net gain, it's only slightly more burn than their busy life would have gotten them anyway. 2-1
    I could see walks earlier in the day would still allow for that busy evening though to occur. 2+1
  • swimmchick87
    swimmchick87 Posts: 458 Member
    I figured maybe it wasn't that it was giving me more calories for doing the same walk earlier in the day, but that perhaps it thought I was burning more throughout the day if I started earlier. Like I said, this is a trend I've noticed for years and years. And again, distance doesn't seem to matter.

    On Thursday of this past week, a regular work day, my distance was 4.24 miles and I got 10,344 steps. I had 10 "zone minutes." Fitbit lists my calorie burn for Thursday as 2,414 calories. Contrast that to Saturday, a non work day. I'd eaten a bit more and was trying to do extra walking so that my adjustment would catch up. I walked 12,172 steps, and 4.97 miles. I had 7 "zone minutes"- only 3 less than Thursday. Yet fitbit says my calorie burn for Saturday was only 2,231 calories- almost 200 less despite walking longer distance and more steps that day. The only difference is that on Saturday, I didn't start walking at all until right before 2 PM. On Thursday, I was at work at 7:30 AM and did the bulk of that day's walking prior to leaving at 4 PM.
  • heybales
    heybales Posts: 18,842 Member
    Active Zone Minutes replaced the Active Minutes on newer watches.
    Charge 4, Inspire 2, Ionic, Sense, and Versa track Active Zone Minutes. All other devices track active minutes.

    Active minutes meant your calorie burn for a 10 min block hit 3 x your BMR rate of burn. Had to hit 10 min to even count at all.
    Usually by that point a workout would have started and HR-based calorie burn would be used. Whether good or bad estimate. As mentioned, lower end of aerobic range is inflated calorie burn.

    Active Zone minutes means your HR is in any of the zones, which also means a workout was started and HR-based calorie burn was used.
    1 min per 1 min in fat zone (most inflated calorie burn zone)
    2 min per 1 min in cardio/peak zone (better estimate of burn)

    If the 10 zone min day was mainly due to time in the fat burn zone, then indeed inflated. Probably all 10 min was.
    Compared to 7 zone min in the same zone would mean less inflated calories.
    Either day you probably walked longer than that time, but were below the HR zones.

    Again - the time you did the workout may seem to correlate to something, but it really doesn't.
    Whether you are moving a mass of weight a certain pace @ 10 am or 4 pm doesn't matter, and Fitbit knows that.
    Your HR obviously could have a difference for a number of reasons, for walking I wouldn't imagine that many since you aren't in terrible fitness shape.

    I have been allowed access to probably 22 different accounts over the years to explain flakiness exactly like this, and during a time I was doing testing for something and asked for volunteers and just confirmed things working in different scenarios.

    This switch to Active Zone Minutes was a negative to calorie burn estimate in my mind, for exactly the flakiness you see.
    It happened already, perhaps they lowered the requirement to start using HR-based calorie burn though so it starts more often daily - which is bad for truly step-based daily activity level stuff.
    Anyone unfit or genetics or meds where HR shoots up higher than body really needs it to be to supply the oxygen needed for the level of effort - gets inflated calorie burn.

    But it does allow people doing lower end intensity to get some "active minutes" without needing to hit 10 min @ 3xBMR rate of burn, which is tad high for low end stuff for some.
    It was not really hard to hit that walking, since that normally used distance-based calorie burn that was more accurate, but you did have to hit 2.2 mph constantly for 10 min, and with hills that maybe didn't happen.

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