Calories Burnt Too Low?

I'm not sure if this is helpful, but I have the same makeup as you...except more like 10% body fat. My resting metabolic rate calories averaged 2,070 calories over the last seven days. That, along with the calories reported from my activities are all feed into MyFitnessPal. This is where I monitor and adjust my food intake to get the weight change results I'm looking for...including holding steady. I've been using this setup for about 3 or 4 years...first using a FR235, then a 920XT, then a Fenix 5+, and now a Fenix 6X. Whatever math Garmin is using, it has given me the exact same calorie burn on all of these devices.

Have you logged in to Garmin Connect and gone under account, user settings and updated your activity class?  I believe by doing so, this will adjust your resting calories.

3704102 said:

I should also mention the wrist HRM is usually way off and low while I am training (HIIT or MTB).

Tips:

• Set your weight
• Set your activity class
• Wear a HR strap when performing vigorous activities

Does the heart rate tracking seem accurate? I just upgraded to the 6 from a 5 plus and am having horrendous issues with the heart rate monitor, most often when I'm working out. It's coming in 30% or lower where my 5 was quite accurate. This has led to all of my workouts showing basically a walking pace heart rate and really low calories burned. Maybe this is your issue? I'm hoping they fix whatever issue this is.. I'm not willing to accept the answer that optical HRM are just inaccurate or that I don't know how to wear it properly when my 5 plus was just fine 

TMK17, I have everything in correctly and I just check it all again. Correct stats and I have the activity number set to 9. It just seems crazy low to me.

And no, the heart rate tracking has been extremely disappointing on the F6. I am coming from an Apple Watch 2, and while I know optical HRM aren't perfect, it was WAY better than the F6 for every activity that I did. And that was with three year old technology. 

Also, does anyone know if VO2 Max is taken into account for calorie burn? As in, does the watch 'learn' you as an athlete or is a base calculation? 

To OP: I noticed the same issue - and found that culprit was how watch (6X Sapphire in my case) sums Active calories (no issue with Resting ones)

In your Garmin watch - Calories value are sum of Resting + Active ones (you can see this on Calories widget) so if this total value is low at the end of day - do the following: on your watch open each of your activity stats (for that day) and sum their calories (activity 1 + activity 2 etc)

If the value of active calories you get this way is higher than what the watch says (Calories widget - check Active ones) - then you are seeing the same issue as I do.

My swimming calories (~650cal per workout) are always in my activity stats - but my Calories widget  doesnt show them. Sometimes happens with walk and running too.

I reported the issue to Garmin btw

To support claim from my previous reply - see attached screenshots taken just after swim today (slower pace, 1.3km)
Swimming activity - 416 (active) calories, but Calories widget shows only 248 active calories
Also you can see (tiny red bars) my whole week looks idle.
This is obviously bug.
Never had this on FR935. 

HI 3704102 - can you confirm that you have similar situation on your device as the one I provided in my previous reply?

Yes I get this also. Activity calories include your RMR calories also so when I subtract my RMR from my activity calories it equals my active number.