Data Field: estimated Fat and Carbs burned from time zones of heart rate

Nobody?
I suppose this is not complicated for developers...

You can count calories burned while athlete is in Z1 of HR as "fat calories" so, 9kcal are 1gr. of fat burned
Calories burned while athlete is in Z2 are 80% fat 20% carbohydrates...so 80% of that Kcal are fat (9kcal=1gr) and 20% carbs (4,5Kcal=1gr)
Calories burned in Z3 are 50:50...
Calories in Z4 are 20%fat and 80% carbs...
Z5 only carbs...

and etc.

All the people would kill to know how much CH and fat they are burning, depending on HR zones and time...

I had an hour to kill so went ahead and had a go at it, I've only calculated the fat calories (not the ch calories).
Once the app is approved (takes a few days) you'll be able to download it here: https://apps.garmin.com/en-US/apps/76ca8d3a-c186-4d65-8bf2-20971e02898b

Really awesome Peter!
Will try it ASAP!!

CH grams burned (if possible in a future) will be quite interesting because athlete will have an approximate idea of how much of the glycogen reserves have been depleted in the activity.
So collapse or fainting fit can be avoided, I mean a physical breakdown caused by hypoglycemia...

Depending of intensity of the activity (related to HR zones) athletes will know when they have to reduce it to prevent full glycogen depletion, or when eat some carbohydrates...and how much.;)

I can see the motivational value in the fat burned in grams for people who's primary reason to run is weight loss, but I'm not sure if the carbohydrate calculation is usefull, I could add it, but I don't know in which scenario's you would be using the figure.

You can't prevent depletion as you simply can not digest enough to keep up. It's not advised to digest more than 70 grams of carbo's per hour (as more is too much for the stomach to handle). (I use less than 70g/hour and even then my stomach starts complaining after a while)

From experience I can say that when I've been running for 5 hours I'm even not any more thinking of eating anything, usually I'm already glad if I can hold what I drink inside my body without having to throw up.

Released version 1.1:

Via the settings of the app (in Garmin Express / Garmin Connect Mobile) you can now opt to see:
* amount of fat burned (default)
* amount of carbs burned
* amount of fat and amount of carbs burned

Awesome Peter!!
Working really nice the previous ("early") version with only fat, I checked manually and working perfect.

For the users that want more accuracy, better if you use Karvonen formula using Garmin profile settings.
Karvonen method is more precise because is related to VO2 max for the most of people so I recommend it.

Go to your user profile and then HR zones configuration, choose %HRR and put your HR-Rest and set the zones as this:

Z1: 50-65
Z2: 65-75
Z3: 75-85
Z4: 95-95
Z5: 95-100(HR Max)

I will test the new version with carbs tomorrow. :D

Released version 2.0:
* Via the settings of the app (in Garmin Express / Garmin Connect Mobile) you can now enable the option to record fat burned and carbs burned to the fit file.

Love this data field, and the fact it records the data in the fit file is great! (I assume the fit file is the summary of my run?

Out of interest, I'm on a low carb (less than 20g carbs per day) high fat diet. Weight loss going well so I'm pleased. After a hard run z4, it says I've burned 30g carbs, but it know I've not eaten than many to burn... What am I burning?

Love this data field, and the fact it records the data in the fit file is great! (I assume the fit file is the summary of my run?

Actually it shows throughout the whole workout how much fat/carbs you 'consumed' in graphical format (viewable on garmin connect), a bit like this:


In the summary it's not shown yet the total, but I suppose I could do that as well. I'll add that to my todo list :)

Out of interest, I'm on a low carb (less than 20g carbs per day) high fat diet. Weight loss going well so I'm pleased. After a hard run z4, it says I've burned 30g carbs, but it know I've not eaten than many to burn... What am I burning?

Well it's an estimate :)
I would assume you'd be burning fat then, but your guess is good as mine.... maybe Susun can better answer your question when she comes around...

Released version 2.0.5:
* fixed the coloring of the graphs. It's advised to uninstall and reinstall the app (for some people the changes don't take effect when do an overwrite-update)