How Pro Endurance Athletes Fuel
Carbohydrates
This article is possibly the most in-depth insight into how professional endurance athletes fuel their specific sports that you will find. There’s a lot to read, but when you finish, you WILL have a new competitive advantage. We guarantee it. ENJOY!
Expect to learn
- How the pro’s fuel for specific sports in both training and racing.
- The difference in carb requirements for Ironman athletes vs Cyclists.
- How the pro’s are able to consume and oxidise (turn to energy) a tone carbs super fast.
- The chronic effects of energy deficits.
- Discoveries (as recent as mid-2023) about optimal fueling strategies for 6-hour+ events.
- And the expert’s opinions regarding low carb, carb loading, carb sources and much more!
Our primary sources of information for this article include:
- Dan Lorang (Head coach of Jan Frodeno, Lucy Charles Barclay, Anne Haug, and Bora Hansgrohe Cycling)
- Robert Gorgos (Bora Hansgrohe Cycling Team Head Nutritionist)
- Tim Podlogar (Bora Hansgrohe Nutritionist and world-leading expert on carbohydrates and nutrition in endurance sports)
- Will Girling (Nutritionist at EF Education Easy Post World Tour Cycling Team)
- Our own expertise after specialising in sports nutrition for multiple years.
Interesting Facts
- An energy deficit is when you burn more carbs than you have stored. Symptoms of repeated energy deficit include long term muscle and bone damage, decreased heart health and more
- According to Dan Lorang and Robert Gorgos, we burn approximately 60g of carbs per hour at low intensities. At high intensities, values as high as 400g per hour have been recorded.
- You can store roughly 550g of carbohydrates in your body. 460g in the muscles (from glucose) and 90g in the liver (from fructose).
- At a threshold (FTP) intensity, on average a cyclist burns 250g of carbs per hour and 0g grams of fats.
- Energy for performance comes primarily from fats and carbs. Fats during rest and low intensity. And carbs during moderate and high intensities. Carbs are also required for regular bodily functions (brain power…).
Do the maths. Your carb stores are full going into a race. You burn 250g of carbs per hour. After only 2 hours and 12 minutes you will be out of fuel. Your body will start to shut down and you will be in no condition to perform.
Therefore carbs are essential for endurance performance. However, there is a big difference between how Ironman athletes should fuel and how cyclists or Olympic distance triathletes should fuel.
Personalising Carb Intake for Your Specific Sport (Training)
One way of looking at it is understanding the required VLa Max for your specific sport.
As the above diagram shows, different athletes require different Vla Max profiles. Simply put, it is a measure of the performance of your anaerobic energy system. Your maximum lactate production rate. Higher values don’t indicate a better athlete, instead, the value you have determines your current athlete type. A higher value means a higher maximum power output and more fast twitch muscle fibers, but lower energy efficiency over a long period of time, and vice versa. You can change your Vla Max in many ways, but when it comes to carbs, this is how you do it…
To raise your Vla Max.
Consume high amounts of carbs even during low-intensity/easy trainings. This will increase your body’s ability to use carbs as fuel and decrease your ability to use fats as fuel. It takes 6-8 weeks for adaptation to occur.
To lower your Vla Max.
You guessed it, consume lower amounts of carbs during low-intensity endurance trainings. For example, a 3-hour endurance bike ride at 35g-50g of carbs per hour. (this seems to be very common in Ironman triathletes). Remember this may take a few weeks to get used to. You will find an increase in your body’s ability to use fats as fuel and decrease your ability to use carbs as fuel. It takes 6-8 weeks for adaptation to occur.
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Carbs for Low Intensity and Endurance Training
During this training, an athlete in a longer lasting, more steady paced sport such as Ironman should consume less carbs per hour compared to an athlete in a shorter, faster sport.
As endurance athletes though, when training at low intensities we should ideally look at consuming moderate quantities per hour. Avoiding very low quantities (<25g per hour) and very high quantities (>90g per hour).
You should have a mixture of liquid and solid forms of carbs for these trainings.
Road Cyclist or Olympic Distance Triathlete
Will Girling says during a 4-5 hour endurance ride you should consume no less than 60g of carbs per hour. Some pro riders will even take in up to 90g per hour on long 5+ hour endurance rides.
In general, on endurance training sessions between 1 hour and 3.5 hours you should be consuming between 40g – 65g per hour (more as duration increases).
Ironman
Essentially you should just be consuming slightly less than the above group.
That means between 35g – 60g per hour for training sessions between 1.5 hours and 5 hours
Carbs for High-Intensity Training
When it comes to high-intensity training it’s simple.
Your body needs a lot of carbs.
Firstly because you require lots of energy to perform at high intensity. Not having enough energy leads to an energy deficit which causes all sorts of problems. Muscle failure, and heart issues to name a few.
Second. Without training your gut to digest high quantities of carbs, your body won’t be able to use them. Instead, lots of what you consume will sit inside your intestines which is what causes stomach pain.
Therefore at first, when you start pushing your carb intake you will likely experience stomach pain, but over time, just like normal training, your body will adapt and you will unlock a new potential. Professor Louise Burke was one of the first to discover this and she explained it in detail in our interview with her.
So how much?
This depends on your sport, when running it is harder to digest high amounts, when cycling it is definitely easier.
According to the World Tour Cycling Nutritionists that we have spoken to, during a hard race or stage, riders will look to take around 120g of carbs per hour. This is considerably higher than the 90g per hour suggested by a lot of nutrition brands. The 90g comes from tests done on amateur athletes who hadn’t done any high-carb training as mentioned earlier.
On average, most amateur athletes who haven’t done high-carb training can digest and oxidise (transfer into energy) 60g of glucose and 30g of fructose per hour. These are the two main types of carb. More on that soon.
Liquids are much easier to digest than solids so a drink or gel with the right glucose : fructose ratio is a great start.
Personalising Carb Intake for Your Specific Sport (Racing)
Here’s where it gets slightly more interesting.
If you participate in a sport that starts easier and gets harder the further on you go then we have a secret for you.
A little secret for any endurance race is to start with slower-releasing carbs such as rice cakes. This allows your body to maintain high fat oxidation rates while still getting carbs in. Then toward the second part of the race, you can start consuming more fast carbs (maltodextrin and fructose gels…)
For cyclists, fueling is pretty simple. Aim to consume as many carbs as possible. 120g of carbs per hour is the gold standard.
For Olympic distance triathlon carb loading is the most important part. More on that below. During the race, you should still aim to take in as many carbs as you feel comfortable with. Mainly on the bike through drink mixes and gels. Target 100g+ on the bike leg. Then depending on how long you take on the run you may want to have a gel to get you through to the end.
Ironman is possibly the most complicated. It is almost worth getting a test done to determine how many carbs you can oxidise at race pace.
If you consume 120g per hour on the bike leg but can only oxidise 90g per hour then 1. you will end up with extra carbs sitting in your digestive system causing discomfort and 2. you may actually suppress fat oxidation. Essentially meaning you become more reliant on the carbs you are eating (limited) and less reliant on stored fat (almost unlimited).
Therefore due to Ironman being a true test of energy efficiency, you may be better to consume 100g of carbs per hour on the bike instead of 120g.
On the run, you will also need to consume carbs. And again we are looking for as much as you can tolerate. Getting as close to 90g as possible. As you have less access to a variety of nutrition when running, we recommend using isotonic gels as they contain a lot of water which will help with digestion. This is the only time we recommend isotonic nutrition as it has been proven to be an almost irrelevant feature (Jumbo Visma Nutritionists).
How The Pro's Consume A Tone of Carbs Without Any Stomach Discomfort Glucose : Fructose Ratio
It is ESSENTIAL to know about glucose : fructose ratios if you want to consume high amounts of carbs. They are the two main types of carbs and you need both of them in order to maximise consumption. Glucose is the main form of carb and fructose is carbs from fruit.
As mentioned earlier, on average most people can only oxidise 60g of glucose and 30g of fructose per hour. With training both of these values can be pushed.
So what should you be aiming for?
The most recent studies show somewhere between a 2 glucose : 1 fructose and a 1:1 ratio is best. Ideally you want to be closer to 1:1. Almost all professional athletes consume a ratio of 1:0.8 that we know of. However, the more fructose you add the sweeter it will be, and some people don’t like too sweet. Unfortunately, if you want performance you need the sweet. There is no way around it.
It is KEY that you ensure the products you purchase contain a correct glucose-to-fructose ratio. If unsure, often lollies such as jet planes contain a good ratio. Also plain white sugar.
You should apply these ratios to pre exercise, during exercise, and post exercise.
The Low Carb High Fat Theory
This idea originated after studies showed that when carb availability in the body was low, athletes used more fat as energy, therefore, saving carbs for later in races. Your body can store over 5000g of fat which is enough to last you much longer than your normal race. So in theory if you teach your body to use mainly fats you can go all day right?
So what’s the issue?
Fats aren’t the body’s preferred source of fuel, especially under high stress (e.g. racing). The process involved in turning fats into energy takes a long time whereas carbs can be turned into energy relatively quickly. Hence why at high intensities (when you need energy quick) your body is only able to get energy from carbs.
No one can max out their ability to use carbs as energy and also max out their ability to use fat as energy at the same time. You must compromise one for the other. When you adapt to being better at using fats, you get worse at using carbs. Therefore you need to find the balance.
If you can use fats reasonably efficiently during moderate exercise and also are able to consume (and transfer into energy) high amounts of carbs during high intensity exercise, then you can find yourself an equilibrium. Continue reading to find out exactly how much carbs you should be consuming to achieve this in your specific sport.
Without carbs, you cannot perform. Without being able to use fats as fuel you cannot perform. Finding the balance is the key.
The Real Question To Ask Yourself
How can I maximise my bodies ability to use fats as fuel during exercise while at the same time maxing out carbohydrate intake and glycogen (stored energy in the muscles from glucose) stores?
During race day you will be taking in high amounts of carbohydrates and be full of glycogen anyway so this is the condition you need to prepare for. This idea was proposed by Podlogar.
- Step 1 is to improve your aerobic threshold in training (Lowering your VLa max). In other words you LT1 or upper zone 2. Through metabolic training (zone 2 and a little bit of zone 3) you can improve this threshold to a point where you burn mainly fats and save carbs. This is key for 95% of athletes.
- Step 2 would be to plan your nutrition to build up from slow carbs to faster carbs throughout the race or in training. More on that soon.
Energy Deficits
“No athlete in a constant energy deficit will be able to train and compete at their full potential”
50% – 80% of endurance athletes train in a constant energy deficit
Relative Energy Deficit in Sport (RED-S). Simply put, when an athlete consistently uses more energy than they take in.
Over time results in long term:
- Decreased bone health
- Decreased muscle health
- Decrease in cardiovascular/heart health
- Decrease in immune health
- And a decrease in menstrual cycle function.
It is the single greatest cause of failure in endurance athletes and it’s all due to a lack of nutrition and recovery. Learn more about recovery here.
Training Your Gut
The best plan of attack is to find out your limit during a high intensity training and then gradually push that limit up to 120g per hour. Start at 80g-90g per hour and remember it may take months for you to reach the goal. Consistency is key.
Also worth noting is the fact carbohydrate oxidation is reduced in the heat and when performing at your limit. As some of you may have noticed, this seems to be one of Tadej Pogacars biggest weaknesses. The Slovenian superstar dominates in the cold but struggles in the heat due to not being able to oxidise as many carbs. This was mentioned by him after cracking on stage 17 of the 2023 Tour de France.
For running, test what you can take in and work from there. As you have less access to a variety of nutrition when running, we recommend using isotonic gels as they contain a lot of water which will help with digestion. This is the only time we recommend isotonic nutrition as it has been proven to be an almost irrelevant feature (Jumbo Visma Nutritionists).
Carbs for Recovery
When it comes to recovery, arguably the most important thing you do is consume carbs.
A common misunderstanding is the most important nutrient for recovery is 30g of protein. Multiple studies have shown this to be not true. In the studies there were three groups.
- Consumed 400 calories of protein.
- Consumed 200 calories of protein and 200 calories of carbs.
- Consumed 400 calories of carbs.
Group one showed the worst recovery and group 3 showed the best. Obviously protein is still important however which is why most pros consume similar to the following after races and hard trainings.
Tim Podlogar stated after a race his riders would always consume 1.2-1.5g of carbs per kg of body weight (at a correct glucose:fructose ratio) along with 25-30g of protein within 30 minutes after a hard race or training. Ideally in liquid form as your body is like a sponge when you finish exercise and it soaks up liquids and nutrients very well.
Carb Loading and Fueling Before the Race
Full carb loading should be done before a hard race. Semi carb loading can be done before a hard training session.
Maximum carbohydrate stores are roughly 460g in the muscles (from glucose) and roughly 90g in the liver (from fructose). On average endurance athletes consume roughly 600g of carbs per day, however, most of this will be burned during a regular day.
Interestingly muscles prefer stored glycogen as an energy source compared to recently transformed glucose. This emphases how important carb loading is.
You only need to start loading 1 day before your target. Particularly during exercise and straight after exercise. Though do not neglect to start the loading phase from breakfast. It is important you maintain a relatively similar intake for each meal in your day (not just overloading dinner). There is no need to force down food but simply have more than you usually would.
The morning of your race you will want to consume more carbs. The amount will be determined by when your race starts. If it is early in the morning like 5am you shouldn’t have as much. If it is a later start like 11am then you should have more.
You don’t want to be eating high amounts of carbs within 1.5 hours of your race as this will decrease fat oxidation and you will run out of energy quicker. So if your race starts at 7am ideally you want to have breakfast at 5am.
Podlogar has a simple strategy for fueling before a race.
If breakfast is 3 hours before the race then you want 3g per kg of carbs.
If it is 2 hours before then you want 2g per kg.
And if it is 1 hour before then no more than 1g per kg.
Ideal foods to have for breakfast that have a high amount of carbs include oats, toast, banana, jam, honey, bagels, or rice. (remember you should usually have a source of protein with breakfast as well).
Ensure you avoid high-fat foods before races as this suppresses carbohydrate oxidation.
Foods high in fibre also need to be avoided in the days building up to the race. This includes salads and vegetables. Reasons for this include; fiber often sits in your digestive system which can cause stomach discomfort. High amounts of fiber in your stomach means there is less area to properly digest carbs. And without fiber on race day, you will likely be lighter.
Types of Carbs
When it comes to high-end performance during exercise, fast carbs are almost always better as they transfer into energy quicker and are less likely to give you stomach pain. This includes blends of maltodextrin and fructose or plain sugar.
However, some nutritionists including Jumbo Visma’s (arguably the best cycling team in the world) say slower carbs do have a benefit. For breakfast, foods such as oats slowly release energy for your body to use throughout the day which is perfect for before a race. If the first part of your race or training is relatively easy then this is where you should look to consume slow sources of energy (rice cakes, energy bars) as the chances of stomach pain are lower. This will give you more long term energy. When trying to lower Vla Max Dan Lorang suggests using slow carbs as well.
But remember fast carbs should be your focus when it comes to performing during a race.
Mathieu Van der Poel won the Tour of Flanders in 2020 and 2022. At over 270km with out-of-this-world power numbers required just to compete, this is one of the world’s ultimate endurance races.
MVDP normalised 400w for the final 3 hours of the race and managed to do 418w for 20 minutes after 5 and a half hours.
The image above shows us the nutrition Van der Poel had during his race. It was then broken down by Kristof De Kegel (performance manager of his team).
At the start of the race he had solid foods and water. In the first 2.5 hours he had 5 energy bars (35g of carbs each) and 3 rice cakes (25g of carbs each) totaling 260g.
From 2.5 hours in until the end, he had 7 gels (196g of carbs) and multiple drink mixes (280g of carbs). Totaling over 700g of carbs for 6.5 hours.
100g per hour in the first part of the race, then 120g+ per hour after that.
So that’s how the pros win races. Do you eat as much as that?
Summary
No carbs = no recovery, no high intensity, no quick energy, no quality training, no speed, and no fun.
- Ensure the products you purchase have the correct glucose : fructose ratio.
- Train your body on the correct quantity of carbs for specific sessions.
- Train your gut to digest 100g+ of carbs per hour during high intensity sessions.