Carb intake confusion

Hey guys,

first off all: thank for the awesome podcast and the great workouts in Trainerroad.
Thanks to commutes and longer trainings, I could listen to almost all of trainerroads podcasts.
I noticed, that there seems to be a development of the carb intake recommendations.
Chad was very skeptical with Carbs in the early podcasts. This changed, when Nate got in touch with Fitzgeralds advice and now the recommendations of Amber are going all in carb intake on the bike.
My experience is here very similar. It helps me a lot, if I fuel my workouts properly.

My confusion is now, which rides I should fuel. Yesterday I did Phoenix with a Brick run. Coach chad said in the workout text, that this ~85% intensity is too low to fuel (a lot). So I ate just one bar, but noticed that I was quite empty during the run. After training I was VERY hungry.

So my question is: Fueling higher intensity workouts properly seems to be opinio communis.
But what about these 85% sessions or the 4h Z2 rides on the trainer.
How should I fuel them to prepare my body for these long endurance efforts?
(My goal is finishing an Ironman this year. I am in the LW FD Plan).
Thanks a lot for the support!

I’m training for Leadville, so similar to an Ironman in that it’s a long day out.

My dilemma is that I want to both 1. Improve my fat metabolism so i am less carb reliant for energy and 2. Train my gut to process 200-300 kCal of carbs per hour - and of course have good quality workouts.

So here’s where I have landed (I’m doing the TR low volume plans, and augmenting with outside rides).

  • For high intensity trainer rides, fuel appropriately with high quality carbs several hours before the workout. No gels immediately before or during. For these 60-75 min rides, I haven’t (so far) felt like I’m underfueled, and if that happens, I want to avoid pure sugar, and instead will eat more a few hours prior.

  • for my 4 hr endurance rides in my base phase, eat a modest amount of high quality carbs a few hours before, no nutrition during. The goal of this is that by hours 3 and 4, I’m hopefully in a state where I’m burning majority fat. I know I’d probably get even more benefit doing these fasted, but generally I’m awake for several hours before I go out and ride, so I just eat when I wake up.

  • As I get into build and specialty phase, I’ll gradually increase the intensity of my endurance rides, and also start to consume carbs during. Every few weeks I’ll do either a “race pace” several hour ride, or race, to get used to consuming carbs at high intensities. The goal of this is to introduce nutrition into my rides, and train my gut.


I like the way @ambermalika described it in the podcast: (of course I’m paraphrasing) fuel to have a good workout, every workout. My current strategy (while finishing up Traditional Base Mid-Volume 3) is to have at least a bottle of sports drink per hour, and then add in some more depending on the effort level. Yesterday I was munching on gummy bears during the ride and it wasn’t quite enough, or at least I wasn’t eating enough of them. Last weekend I was eating pancakes (dry, not messing with syrup on the bike :joy:) during Mount Bear.

@Mikael_Eriksson made a good point in his That Triathlon Show podcast recently, Q&A #19 (I am having trouble finding a link to the episode, but from the Episode Notes in my podcast app):

Effective training is the best way to improve substrate utilisation (and therefore performance) - of both carbs and fats!


Thanks for the shoutout @matthew.weigel, here’s the link.

In terms of fasted training, a little goes a long way. Depending on how often you train, I think one (4 rides or less per week) or two (more than five rides per week) fasted workouts per week is appropriate. No need for anything more than that. And I would also say that the fasted portion of a fasted workout really doesn’t need to be any longer than 45-90 minutes, depending on your level.

For example, if you do go out for a 4 hour ride, don’t even think of doing the entire thing fasted. You can do it, but it will only cost you in the long run. It’s more than enough to do up to at most 90 minutes of that ride fasted.

Note also that these would for me be the MAXIMUM recommendations in terms of number of fasted workouts and durations. I still (a whole 2 weeks later!) stand by the statement that this is just icing on the cake - most of the substrate utilisation changes you are after comes from the actual training you do, and a lot of it comes down to - how much can you improve your fitness.

I also agree with @ambermalika 's comments.

I know I’m posting a lot of charts today, but the week’s training is done, and it’s raining, and I find exercise metabolism fascinating so bear with me:

Solid line: VO2max 57.6, VLaMax 0.3, diet: “Endurance diet”, fasted rides: as per my recommendations aboe

Dashed line: VO2max 57.3, VLaMax 0.39, diet: LCHF borderline ketogenic, fasted rides: a lot, and a lot of long ones


As you can see, the solid line has a slighlty better fat oxidation, despite the dashed line rider doing a ton of fasted rides and being an LCHF/keto athlete. The difference in VO2max is almost negligible (1%, so within the measurement error tolerance) whereas the difference in VLaMax is larger (30%).

And the difference in VLaMax is largely a result of training.


good point to discuss! With all the complexity of nutrition I find it is sensible to follow recommendations that are simple and easy to implement. Matt Dixon has IMHO very good fuelling advice. There’s two episodes on the Purple Patch Podcast, one of him and one with his nutritionist Kyla. Some key takeaways:

  • consume some carbs 1-2h before a workout, doesn’t need to be much
  • workouts up to 1h don’t need extra fuel
  • everything above 1h should definitely be fuelled
  • consume post-workout nutrition after every workout
  • have the sugary race nutrition in workouts that are most like your race (eg race simulations, long bricks)

Even if you only do Pioneer of 1h, your effective workout time with brick is at least 1h20-1h30 so you should definitely fuel.

I have tested carbs during high-intensity 1h workouts recently after the podcast and did not experience a benefit compared to before. That may be individual though.

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Great stuff. Gives me some good pointers on how to adjust my training.

These charts are great by the way. Are these from RER tests?

I’m behind on your podcasts, so haven’t gotten to that one yet. I’ll skip ahead, and listen to that one next.

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in this graph the dashed and solid lines look to me pretty much similar if you take some measurement error and variation along.

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@schmidt The difference at FatMax is 30 kcal/h, ~6.7 %. The measurement error is <2.5%. You’re right that they visually appear very similar.

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@DaveWh They’re actually from critical power testing analysed using a software called INSCYD, which has been clinically validated to be as accurate or better than gold standard metabolic carts. Accuracy 2.5% or better.

And it’s worth pointing out that many labs have cheaper metabolic carts that are far from gold standard, so they would be significantly less accurate.

As reference values, lactate threshold measurements have an accuracy of 5-10% and threshold estimation using field tests is even less accurate.


Thanks for the detail!

I’ve listened to many of your episodes and learned a lot. thanks for your work and efforts!


Some advice from the INSCYD website on how to improve fat metabolism:

  1. Avoid lactate accumulation
  2. Lower carbohydrate intake
  3. Increase VO2max

The simplest advice is often then best!


You guys are really great! Thanks for that detailed feedback! I appreciate!

For the German speaking: Today the triathlon crew cologne released a video on just that topic:


good stuff from these fellows. some translated take-aways for everybody:

how do you train your fat metabolism?

  • train twice a day (irrespective of nutrition)
  • consume less carbs during workouts. in particular short ones - just water. this does not count for long workouts! here, start consuming 30-60g per hour from maybe 1h - 1h30 onwards (eg 2 bananas)
  • train fasted (low intensity)
  • consume caffeine

recovery without post-workout nutrition (“recover low”) is at best controversial

“sleep low/train low”: go low carb (but protein/fat) after a high intensity workout and then easy session the next morning. this improves TT times and 10k run, probably due to enhanced glycogen stores, within only a week (3x through). applicability so far not clear.


Great stuff here and big thanks to @Mikael_Eriksson! The thing I struggle with and perhaps because I’m relatively new to structured training and I’m almost 50 but I find for the harder workouts when I do them first thing in the morning, say 6ish AM, like tomorrow Spencer +3 which is an hr but an IF of .95 I seem to do better if I have a gel before hand and perhaps 25g of carbs in a drink during (say tailwind or roctane). Is it all in my head as my carbohydrate stores should be enough?

I can say in general I have a higher than avg. metabolism and heart rate (probably due to poor conditioning, I get in the low 190s during VO2 Max efforts) Does that matter at all?

Your body uses carbs over the course of a night, that’s why when they talk about doing rides in a low carb state on the podcast it’s always “first thing in the morning, before you have breakfast.” You’re definitely low on liver glycogen when you first wake up in the morning.

As @matthew.weigel says, plus RPE can be higher in the morning compared to afternoon, and that extra gel can give a quick sugar boost to your brain which lowers RPE.

What number your HR is doesn’t matter, no. That is admittedly unusually high for your age, but just goes to show why age-based formulas don’t work, never have, never will.

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Makes sense thanks Guys! Funny I heard about not using age formulas for HR on an interesting podcast, what was it? Or right that triathlon show podcast!!! One of the Best out there, I highly recommend to it not just triathletes!

A Sky block – note the last session, done “fasted” and with only 30g of carbs/1 banana to fuel a 5hr ride (which is consumed at the 90min mark). Is it because their physiologies are so trained that they need more time to reap the benefits of fasted/low carb rides…or is it a matter of old school/old habits (although it is Sky, can’t really see them sticking to ‘old school’ methods). Thanks!

I’m pretty dubious about those things sky put out. That final 5 hr day the total energy output must be ~4000kcal and the total input <2000kcal. Doesn’t really stack up to me.

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Why not? My 5hr fasted weekend rides are ~3200kcal and I do them with water only. Pretty sure a pro rider can toodle around in “zone 1-2” for 4.5hr on a single banana.