Suddenly burning significantly fewer calories

[molten_dragon]

The last few days I've noticed my calorie targets have seemed rather low, despite decent amounts of activity.  I looked into it some more and it seems like whatever it was happened on Friday March 24th.

On Thursday March 23rd my activity overview is:

11,458 steps, 4 floors, 5.52 miles, 3299 calories burned

On Friday March 24th my activity overview is:

13,937 steps, 14 floors, 6.36 miles, 3213 calories burned.

Other days before and after that with similar activity levels show very different calories burned.

Sunday April 2nd:

10,968 steps, 19 floors, 5.35 miles, 2852 calories burned

Saturday march 18th:

10,697 steps, 7 floors, 4.85 miles, 3285 calories burned.

I didn't change anything about my settings or the way I use my fitbit.  I wear it on the same hand, it's set to the same hand (dominant), my plan intensity is the same, the way it counts my calorie target is the same (sedentary).

Does anyone have any ideas why the major difference in how many calories I'm burning starting on March 24th?  Did Fitbit change something in their method of calculating things?

[WavyDavey]

Hi @molten_dragon,

I don't think the calorie calculation has changed recently. Two things I look at it terms of effort is Active Minutes and Heart Rate, as I find them better indicators of energy expenditure than steps and distance. I have days where I get 2500 steps and burn more calories than days I walk twice that many steps. So I would compare the Active Minutes on those days and look for differences.

As far as I can tell, the calories burned is largely based on heart rate data, so that would be something to compare on those days also. For example, I had a workout with weights yesterday that was 90 minutes in duration, but only generated 10 Active Minutes, and then went for a short walk that generated 30!

So I would start with comparing Active Minutes and heart rate between the days and see if there's enough of a difference to explain the change. Hope this helps.

[molten_dragon]

So I dug into my export data a little more.  It seems like it's registering a lot fewer fairly active and very active minutes, and a lot more lightly active minutes.  For example:

Date	Calories Burned	Steps	Distance	Floors	Minutes Sedentary	Minutes Lightly Active	Minutes Fairly Active	Minutes Very Active	Activity Calories
3/13/2017	3,434	11,253	5.17	13	1,099	222	34	85	2,040
4/1/2017	2,887	11,334	5.12	5	1,084	324	5	27	1,514

I'm not sure why that's suddenly changed though.  I'm not sure how to see historical heart rate data, so I'm not sure if that's affecting it.  Most of my activity is about the same from day to day though.  A workout in the morning that's either weights or running on the elliptical, and the rest of it is pretty much walking. 

I wonder if something's wrong with my heart rate sensor.