Kind of confused here about which I should track when trying to top off energy stores during a long ride. I know that its nearly impossible to take enough on board over 5 hrs to maintain levels, but it seems simplest to have my Garmin monitor calories rather than KJ, and just try to keep up with calorie depletion. Any arguments for KJ that I should be aware of? What am I missing?
Thanks!
The math just happens to work out 1:1. So every kilojoule of work you do you burn 1 dietary kilocalorie. There is noise that is hard/impossible to account for in your body spending energy to regulate its temperature. But for the most part you just take on your 60g (240 calories worth) of carbs/hour because any reasonable effort is going to put you over that burn rate anyways.
Neither!
They are both made up and do not correlate to Food In and Energy Out
This is not relevant to the discussion. A 5 hour effort from a trained cyclist is going to dominate the calorie expenditure for that day. OP is asking how to stay fueled, not how to lose weight.
Too bad team Sky team didn’t know that calories were made up when they were driving Froome’s weight loss to a few grams precision during this year’s Giro!
But coming back to the OP’s question - really not much difference between Calorie/kJ, as long as the source of data is an actual power meter.
we’re simplifying the calculation to say it is 1:1. That is assuming you have the near perfect 25% pedaling efficiency, otherwise your energy expenditure is greater than kj.
Ok super helpful. Thanks. I won’t worry too much about it and will just estimate 1:1. I’m not on Team Sky at this time so this should be close enough for me. 
Much appreciated.
For anyone looking for a bit more reading on this, we actually have an article on this exact topic within our Help Center
Ok, I’ve read the topic, various google links, and the above blog post and I’m still a little confused.
On my ride today:
52 miles 3.5 hours
1978 kjs
2353 calories (reported by Garmin, Strava, and Interval.icu)
If kjs and calories are roughly equal for cycling where is the 2353 coming from?
If I’m tracking calories which should I add to my daily calorie budget?
kJs. Generally they estimate based off HR or time and distance. If you have power it’s the most accurate.
Yes, I have power so the Kjs are right on. The calories are some kind of estimate but the not the roughly one to one people say to use.
Got the same thing. When you put your ftp, body metrics etc it starts to try to give you an (accurate) cal measurement. How accurate however i don’t know.
I have had a chat with Garmin about this recently. They have released an update (on about 14Jun2021) where Total Calories burned is your “resting calories” + “work performed” during that workout. So in your example you burned an additional 1978kj (work performed) during the ride.
To specifically answer your question, you should use the 1978kj to add to your caloric budget. The additional 350 calories in the 2353 number is already accounted for in your BMR.
As an aside the Total Calories is the number the MyFitPal pulls from the Garmin API for your additional calorie budget, so if you are one of those folks that relies on MFP to track your calories and pull your workouts in from the Garmin ecosystem, it is over reporting your daily caloric budget starting on about 14Jun2021.
Which is stupid, because no one actually wants that number.
A bit crazy from garmin to suddenly change that field. If you don’t have a powermeter, you wouldn’t realise it’s off, and could well over-fuel afterwards.
Is it possible to get your garmin to forward on the kj value instead? (to another app I mean, like MFP)
The issue here is that MFP pulls from Garmin. Garmin does no pushing. As far as I know, we now have to manually put the correct info in.
I have put in a ticket with MFP, and encourage others to do so as well, but I have heard nothing back from them yet.
If anyone happens to have a better method I would love to know about it!