Question on Carbs/Calories

I’ve headed the advise on the podcast and elsewhere on fuelling rides appropriately
( I used to head out with a single 600ml bottle of water no electrolytes and scoff at others taking gels) :roll_eyes:

I now head out on a 2-2.5 hour ride with 2x 950ml/32oz bottles each with 60g of carbs + electrolytes and 2x gels (70-90grams carbs/hour)

Whilst @Jonathan makes a great point about calories burnt during a 1 hour ride at only 100watts matching the calories in recommended carb intake, my question is more about carbs needed and available glycogen levels

As example last week I rode a “tempo” ride for 2.5 hours and consumed 180grams of carbs on the ride.
XERT has estimated my carb usage was 167g carbs and 1670calories
(This same ride can be up to 300g carbs and 2 hours of riding hard)
But in my case with 167g burnt, is taking in 180g of carbs too much? What type of reserves do we hold in stored glycogen in blood/liver/muscles? and should this be considered/calculated too?

Or am I basing my logic off a prediction (XERT) that may be wildly inaccurate

You’re assuming XERT is correct regarding the split between carbs and fat which I doubt to be honest. I wouldn’t worry about what the software says and just eat as required.

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Yes, complete assumption from a single cycling platform, I know :roll_eyes: but non the less, certainly curious about how many carbs vs fat are burnt in a ride.

But if total calories burned are ~1500 and I’m quibbling about 100g of carbs (400calories)? Then really not worth thinking about

Not sure how close their estimate of fat vs. carbs is.

Fat is more like 9 cals per gram, and they have estimated that you burned 101g of fat (900 cals), of the total 1673 cals. Don’t worry about eating an extra 13 grams of carbs. If you eat excess carbs that your body doesn’t need at the time (to burn or to store in muscle and liver), they will be turned to fat. likewise, if you consume a little too few carbs, you will make up for that with your regular meals for the day.

So, unless this is some plan you have to lose weight on the bike, you probably should refuel for those 900 cals, too, but some of that refueling will need to be protein and fiber and healthy fats, etc.


Yes, and interestingly (if the predictions are in fact in the ball park) the same ride/route at SweetSpot (25min shorter) has the carb consumption at 256g

its not just about pure grams of carbs consumed/ metabolised. carbs make the ride feel easier, help recovery, ward off post ride excess binges. your body wants to maintain glycogen levels, your brain likes carbs and lactate. also your liver doesn’t really want to convert carbs to fat. its an expensive process, while fatty acids store easily. we are not like light switches, we are complex systems

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So should we ever expect to rely on glycogen stores to fuel our ride?
Or try and match expected carb requirements with gels/mix?

I went for a 1.5 hour ride this morning, 2x gels and 950ml bottle with 60g carbs + banana

Ride estimate was 169g carbs
I took on 120g (during ride) + pre banana = roughly 160g carbs

Would this be a good strategy?

For context this was a SS/Threshold ride with a current FTP of 269

it depends how fit you are. if your ftp is high and your lactate 1 threshold also, then 1385 kcals may be low to moderate on carbs. if your ftp is low, then 1385 may well be highly fuelled by carbs and little fat. i doubt your app/ device really knows. if you eat a good meal the night before, breakfast before hand, then 2 food items should be plenty. i’d say you got it about right. drip feeding sugars into the blood stream is the key.

Interestingly (before structured training) I used to ride the same route much faster with only 1x gel

However, I’ve noticed that this morning I’m still feeling fresh, had a post protein smoothie and not even Hungry….

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But, I’ve noticed there are varying recommendations,
ie using Precision Hydrations calculator they don’t even recommend any carbs…

If I extend to a 70km hot ride they up to 30g / hour
This is interesting as I’ve often heard Andy from PHrecommending 90g+/hour for Races, however, I guess these are pro athletes with stupid high FTP

Seems to be related directly to duration and intensity (obviously)
Maybe I’m simply overestimating requirements for the shorter durations I usually work for

@thomas1, I think you may be overthinking things a bit.

If your diet is balanced outside of riding (meaning you are eating enough calories daily to maintain your body weight and non-cycling activity levels), then you main concern is to replace calories burned during workouts on 1 to 1 basis.

The fact that XERT gives grams of fat (9 calories/gram) and carbs (4 calories/gram) burned, seems to be causing you some confusion. I don’t think the SOURCE of the calories you use for the ride doesn’t necessitate that you replace them with the same type of calories upon replenishing.

I recently watched a helpful video from Dialed Health, linked below (starts right at the spot). In this video he talks about how to replace your workout calories - he suggests to mostly do it with carbs. I suggest watching the whole video if you have the time. Explains how you should approach nutrition and macros at a high level, and then gets into workouts and how to replenish.

Unless you’re trying to lose weight, you should focus on replacing all the calories you burn in workouts - especially if you want to become a faster/stronger cyclist.


Thanks @dhengen - I’ll give the video a watch.

Yes, probably overthinking it, as @chad always mentions on the podcast us cyclists are often thinkers, plus throw in the gift of ADHD and I usually get a bit obsessive - crazy combo! I’m sure @Nate_Pearson knows what I mean. :stuck_out_tongue_winking_eye:

But if my understanding is correct are we not supposed to focus on carbs as a fuel source whilst *on the bike?

I also feel like most of my rides don’t warrant the 90g/h carb intake as most are <2hours

I’m not focused on weight loss, however, after 3 years of consistently weighing between 74-76Kg I have noticed my weight increase steadily to over 79kg in a couple of months since taking on more carbs during rides/runs.

I guess if my diet stays the same then this is logical, simply based on taking on additional calories over and above my usual eating habit. But maybe there are other factors or diet changes that have gone under the radar….

Will probably keep overthinking this :joy:

Yes, you are correct. You should focus on fuelling while on the bike. I usually base my intake around intensity. The carbs you take on the bike should count towards the replacement calories of the workout. For example:

2hr Z2 ride, depending on your FTP, you might burn 1,000 calories. If you fuel at 60g carb/hr (typical Z2 range), that would be 120g of carb (or 480 calories, since each gram of carb has 4 calories). This means that even though you fueled adequately on the bike, you are still in a 520 calorie deficit and (unless you’re trying to lose weight) you should replace those calories off the bike, typically with carbs as I mentioned above if you’re already hitting your protein targets (maybe some fat? I’m not sure about that).

I hope this helps. I recently took the time to understand my diet holistically with regards to Active BMR and getting my macros right from that and then adding in workout calories on top of that. It really helped me piece all this nutrition together. The bike and that fuelling is really just a subset of all the other fuelling you do throughout the day for your ‘normal’ life. It’s actually been extremely liberating.

With regards to your weight going up… that could be concerning, but it could also just be a more natural place for your body. I would ask you some followup questions; has your muscle/fat mass increased during this time? What’s happened to your FTP? How do you feel in general? If you are gaining weight and fuelling workouts, then you’re definitley in a calories surplus, but whether or not that’s ‘bad’ depends on your goals. If you take the time to track your normal eating through an app like MyFitnessPal for even a week or two, you’ll probably learn some pretty insightful things about your eating habits and subsequent weight gain.

Good luck!

I personally have trouble physically consuming that much sugar on the bike. That much sugar means no plain water in the 2nd bottle because I can’t fit 180 grams in one bottle without making it sickly sweet. I also don’t want to pay $1 per gel for regular training rides. I’d rather carry an extra $.25 banana or two.

I just eat some carbs in my meal before the ride, take a banana or two and a bar along, and have one bottle with maybe 60grams of maltodextrin in it.

Be careful with your dental health when trying to guzzle down a lot of sugar per hour. Try and chase drink mix and gels with plain water. Brush your teeth after rides. After decades with no cavities, I ended up two two a few years after starting to use sugar on the bike. (Yes, I know, it’s anecdotal.)

If your Xert signature is dialled in correctly ( a bit like making espresso) and you are working at the efficiency that Xert uses in its calculations then you shouldn’t be too far out. As a result of a gas Exchange test a few years back I found I was only 19% efficient at my endurance pace as opposed to the 22% I think they use. I estimate this increase my CHO consumption by about 10% over what they calculate. Anyway its a whole lot better than assuming all your body uses is sugar and eating far far too much of the stuff on the bike.

The App makes a half decent stab at it. Using what they call your Peak Power, your Threshold Power and your High Intensity Energy it constructs an approximate Fat/Carb Oxidation Graph against power using their calculation of LT1 as the point just beyond Fat Max. It then works out a second by second consumption of Fat & carbs on your Head Unit. As I’ve said previous if your numbers in Xert are right and you are averagely efficient then its more than likely very close.


That’s almost exactly what I do so I’d have to say - Yes

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Thanks @carytb. @thomas1 The Fat/Carb feature of Xert can be used in a variety of ways. As @carytb points out, if your signature is good you can use these approximations as improvements over using plain calorie calculations that you might find elsewhere.

Remember that these are based on your power data and do not account for the demands from basal metabolism. I.e. you need to eat carbs, protein and fat as part of regular daily intake. Hence, if you were to measure your fat/carb demands while riding, they would be higher than what you’ll see from our fat/carb counts. Remember to eat breakfast, lunch and dinner as you normally do whether you ride or not. You should also ensure these meals meet your micronutrient demands as well.

While on the bike, you should be most concerned about replenishing your carbs. Your gut can process roughly 60g of carbs per hour but can be trained to handle more. Pros are consuming 100g+ per hour, for example. You’ll need to experiment and perhaps try different approaches in order to find the right type and quantity that doesn’t cause G.I. issues. But fuel early and regularly while riding. If you can replenish the carbs you burn while riding, this is better than doing so after your ride. (This is something many athletes don’t think about). If you’ve trained your gut and you’re not riding at too high an intensity, you may not even need to eat carbs afterwards. Again, experiment a bit, but this is what we should be aiming to achieve.

If you can get it right, you’ll be surprised at how strong you feel at the end of rides and how you feel afterwards too. You’ll know when you get it right when you can push for a breakthrough deep into a long ride. That’s the tell-tale sign you had the fuelling right.