Data Field: Fat Burner

When you say pause the exercise do you mean that you go in power save mode or do you just stop and start the activity?

I'm afraid myself don't have much settings to play with, I can only specify that the field should be stored in the fit file and the value to store in the FIT file. The actual writing to the fit file is something that the API handles, so likely it will be in Garmin's hands...

When you specify to not record values to the FIT file this section is skipped and explains why you don't experience the issue then.

Hi Peter,
sorry for late answer ... I was 'on the road'...
At the end of on exercise (on Fenix 5x, Chronos and others) you can choose - to skip - save - or pause and follow up later.
In don't understand your last sentencence. When installing your data field recording is standard setting. It was quite difficult to find out that this gives the unexpected problem and I wanted to let you (and others) know ...

Thanks for your investigation Derechte, I appreciate your research, but as mentioned before I'm afraid it's not in my hands to fix.

I can provide you with 2 workarounds, I realize they may not be satisfying, but it's the best I can do:
* Record to FIT and Do not choose to pause your activity and resume later (just start a new one instead)
* Do not record to FIT (by turning of the write to fit in the settings) and use the pause and resume activity functionality

Hi Peter, linear interpolation is really awesome!!

Now carbs consumption is better estimated. In the past when you were almost at the top of a HRzone (specially Z3), the consumption was quite underestimated.. for example.

Well, I was using a powermeter so I have kJ data of what I'm puting on pedals.
As 1kJ is 0,24Kcal but... there is an efficiency (body processes also consume energy, and lots of energy lost as heat) of around 25-26% in most athletes... we can assume that 1kJ measured is really 1Kcal (calories, as displayed in Garmin) burned.
Strava also assume that inefficiency when you have kJ data provided by a powermeter.

While in route, Garmin measures Kcal same number as kJ (I suppose following what I told before) so then Fat Burner is taking the proper amount of calories to make calculations.
BUT, when you upload activities to Garmin Connect, then calories recorded will change!!!
In my case, as if I had an efficiency of only 16% instead 25-26% so then...calories recorded in the activity (seen in Garmin connect) are more... so if you make calculations of calories of the fat and carbs recorded you can't find coincidence.

All people assume near 1:1 proportion of kJ:Kcal as described for all authors, assuming 25-26% efficiency for all people, I can't understand Garmin is doing this... hope someone explain that.

Hi Susun,

Which Garmin do you have?

I am not fully sure whether I can follow you, but it seems you are delighted with the approach of your Garmin unit right?

I am on the opposite side who hates that his Fenix 3 HR calculates calories burnt using Firstbeat 2nd generation algorithm except for when a powermeter is present. I mean I believe that also in case of having a paired powermeter my watch should stick to the Firstbeat method instead of assuming any sort of metabolic efficiency. In other words I do not think that everybody has the same net metabolic efficiency of 23.74%. Just the opposite, I read dozens of researches about metabolic efficiency

But since I do not use Garmin Connect actively, I cant perfectly confirm whether you are right or not. My restricted expereince tells me that sometimes KJ number an Kcal number are the same, so there is no recalculation of calories, but sometimes I see that even when I had a powermeter with me, Kj and Kcal numbers are different. And I love the latter, and again I hate the former case.

See my posts here:

https://forums.garmin.com/forum/on-t...65#post1060565
https://forums.garmin.com/forum/on-t...22#post1060622
https://forums.garmin.com/forum/on-t...25#post1060625

My watch crashed during an activity. I restarted it and could resume the activity without problems. The only thing that was missing is that FatBurner apparently stopped working after the resume, i.e. fat and carbs burned were no longer recorded / calculated.

Can you check on your watch whether there are any error logs?
More specifically in the root of the device there can be an err_log.txt, in the folder apps\logs there can be a file named ciq_log.txt

Hi all,
can you confirm zones are


Z4: 95-95
Z5: 95-100(HR Max)

instead of

Z4: 85-95
Z5: 95-100(HR Max)

I got an interesting result while testing the pool swim app of my Fenix 3 HR. Calories was being displayed as 15, while fat in grams was 2. It is interesting, because I set fat as 9 kcal/g.
My bet is that since wrist HR is disabled in pool swim, my HR was actually considered as zero, so the interpolation went in a way, that my fat proportion increased to over 100%. Can it be, Peter?

It is just an "out of curiosity" issue ......

Normally it shouldn't increase over 100%, but I'll check my unit tests. I'll have to come back on that. :)

Hi all,
can you confirm zones are


Z4: 95-95
Z5: 95-100(HR Max)

instead of

Z4: 85-95
Z5: 95-100(HR Max)

well spotted, fixed it.

I got an interesting result while testing the pool swim app of my Fenix 3 HR. Calories was being displayed as 15, while fat in grams was 2. It is interesting, because I set fat as 9 kcal/g.
My bet is that since wrist HR is disabled in pool swim, my HR was actually considered as zero, so the interpolation went in a way, that my fat proportion increased to over 100%. Can it be, Peter?

It is just an "out of curiosity" issue ......

Verified with a new test that 0 heart rate is treated the same as rest heart rate. So it maxes out at 100%.