does this exist? thinking a calculator that factors things like average watts, ride duration, etc. pretty sure at 60kg and at my power output… i might not need 120g/carbs per hour.
That’s not how it works. The fat burned on a daily basis is not free energy. You’re trying to maintain an energy balance.
You’re right though. You may not need all those carbs based on training length and weekly volume.
2 Likes
I use average power times 3.6 divided by 4 times .45 to get carbs per hour.
Times 3.6 gives total calories burned
Divided by 4 converts calories to carbs
Times .45 gives how many carbs I want to replace while in the bike per hour of biking.
2 Likes
Your body burns carbs and fat to produce energy. Some of that goes to the pedals. Most gets wasted as heat. That bit is an unfortunate side effect of the laws of physics and chemistry. Some of us are more efficient than others. And actually, our individual gross efficiency tends to rise with power, up to a point (over your threshold you recruit more and more fast twitch fibers, which are less efficient).
That said, say you average 100W for an hour, or 3600s. That’s 360 kJ.
At higher power, we probably have GEs ranging from 18-25%. They’re a bit lower at lower power. If you assume a 25% GE, you figure that we have to burn 360 / 0.25 = 1,440 kJ of energy. You multiply by 0.239 to get that in calories - that’s 344 calories. So, at an average of 100W, you burned at least 344 calories of food, and actually you almost certainly burned more than that.
1 Like
I think an app would be overkill. Dr. Alex posted a little table many times on the forum that is probably useful.
Personally for an under 2 hour easy endurance ride, I’ll probably just take a banana and a bar. If I do a 2-3 hour hard hitting group ride, I’ll bring as much sugar as I can cram in a single bottle.
If I’m I’m doing VO2 max or threshold intervals I’ll drink some sugar. I don’t think it has to be an extraordinary amount for a 1 hour workout - like a few hundred calories worth which is like 75 grams.
I did a 5 hour gravel race/fondo. I put 1200 calories of sugar/malto in my hydration pack and ate another 300 calories in solid food. That works out to about 75 grams per hour. By the end, my stomach was slightly nauseous so I think I was near my max sugar ingestion. My performance was great. Never bonked nor felt like I ran out of energy.
Though we often read about 100-120grams per hour, I wonder how many athletes really get that high in practice. Maybe you have to for Ironman or something but for regular training, it hardly seems necessary.
2 Likes
interesting. ironically i get 80g/hr which was my target in my last long race.
do you have a link or keywords i could search to get the table? edit: found it.
1 Like
You can also check out the Saturday mobile app (published by the very same Dr. Alex Harrison), which helps determine fueling requirements for individual workouts.
It’ s a subscription product, and I’ve been using it since it came out. Very happy with it, and glad to pay the subscription, because I’ve definitely found better performance in races and better energy management in training by following the app’s recommendations.
5 Likes
I think it depends on rider power output and length of rides. I’m frequently in the 100-120 g/hr range for longer training rides, which for me are usually 260-290 NP. The longer you ride, the more you’ll need throughout, and the higher the power, the more you’ll need as well.
2 Likes
Not really how it works. I’ve had a coach for a while and it’s not that complicated.
These values are all based on that you’ve eaten properly before the ride. I aim for 1.5-2g/kg of carbs for most of my meals.
Easy endurance under 90min: can be done fasted, or 20-40g in total.
Any endurance ride over 90min: 60g/hour
Any type of intervals or hard ride 80g/hour
Back to back long endurance days, for example training camp or trip abroad: 80g/hour
Again, it doesn’t look super much, but if you’re having enough carbs for allt the rest of the meals, measured carefully, it should be a good starting point 
Look at @Dr_Alex_Harrison‘s app, which helps. But to summarize my take on the many discussions we have had on this topic:
- Weight does matter, but not as much as many think. That is because caloric needs depend on the total energy expenditure (= average power times time).
- You don’t need a lot of power to use up 90 g/h worth of energy. Even people with a pretty low FTP can manage that at endurance pace.
- Many will argue that you don’t need to fuel shorter (< 2-hour) rides/workouts. That is correct, but …
- It does not mean that it doesn’t matter whether and how you fuel (or not) as far as performance and consistency is concerned.
- Taking in more carbs can be trained.
1 Like
To add something to this point:
Yes, it’s correct that you don’t need to fuel shorter rides to get through that ride well.
HOWEVER, if you have a demanding training schedule for the week, you may very well benefit greatly from fueling those shorter rides, indeed ALL rides, in order to improve recovery and be better prepared for the NEXT ride rather than having to replenish all your glycogen reserves from the subsequent meals.
I now fuel EVERY ride, and I feel a million times better throughout my week, and I’m able to work harder, than I did before.
6 Likes
So, I was wondering how much extra intake is needed? Just living life is burning, how much? Training is burning significantly more. Hence if your objective is weight lose ( not mine) its the extra energy that is helping; but if you are training then the extra fuel, rather than the whole lot, that is pertinent?
Going from memory, the human body’s efficiency is around 21–23 % when cycling. Meaning that to produce 100 W of power, the body has to roughly produce 4x the amount. That’s why, roughly, the kJ produced at the crank “equal” the amount of kCal you need to take in. The reason is that the conversion factor (going from kJ to kCal) approximately matches the body’s efficiency.
What is not included is the energy expended by the body during recovery (to heal the damaged muscle tissue, etc.).
1 Like
Adam Pulford (Time Crunched Cyclist Podcast (ep. 200)) uses 40-50% of the kJ per hour, then divides by 4 to convert kJ to grams (carbs) without saying it. So your 45% is the average of what he recommends.
Your first two steps gives the kJ per hour, then converted to grams (of carbs) per hour. Most modern head units record kJ, so it’s easy to use that number as a reference point.
So if you know the average kJ per hour (total kJ / duration) from previous activities, you can guesstimate the required carbs by simply using a range (40-50%) or the average (45%), to get total calories (divide by 4 to convert to grams of carbs).
Most labels show grams of carbs, so I use that to add up all food, bars, bottle mix, gels,etc., to get my lower and upper limits.
1 Like
If you are talking about a “long race” then you will always be in a deficit so eat as many as you can tolerate. There is no way you can eat as many as you burn.
1 Like
OOooh a timely question 
.
Make sure you tune into today’s episode of the Ask A Cycling Coach Podcast (Spetember 12th, 2024). We cover a study that directly adresses your question.
Without giving away too much, Dr Podlogar and colleagues just completed a study that challenges the current guidelines. The current guidelines do not consider body size in the suggested carbohydrate intake during exercise. The study we discuss has been accepted by the International Journal of Sport Nutrition and Exercise Metabolism but it hasn’t been published online yet.
Dr. Podlogar sent us a copy of the final draft but this is a link to the abstract.
We discuss what this means for us cyclists in the podcast episode so I can link to the episode when it’s released later this morning :).
3 Likes
Here’s the link to today’s podcast!
And we dive into this specific question at this time point.
If you have any questions about this study, comment on YouTube video and I’ll do my best to answer them! 
2 Likes