Carbohydrate Fueling for Endurance Sports: How Many Carbs Per Hour Do You Need?
- Marine Lenehan
- Aug 16
- 7 min read
Whether you are cycling, running, racing in a triathlon, or taking part in another endurance event, carbohydrate fueling can make a major difference to performance. But fueling well isn't simply about consuming as many carbohydrates as possible. Your body has different pathways for absorbing and using carbohydrates, and understanding these pathways can help you decide how many carbs per hour you should consume, which foods to choose, and how to train your gut to tolerate more fuel.
For endurance athletes, one of the most important concepts is the combination of glucose and fructose, which use different intestinal transporters: SGLT1 and GLUT5.
How many carbs per hour should you consume during endurance exercise?
Your carbohydrate target depends on the duration and intensity of your event.
Exercise duration | Recommended carbohydrate intake |
<60 minutes | Usually little or none required |
1–2 hours | 30–60 g/hour |
2–3 hours | 60–90 g/hour |
>2.5–3 hours | 90 g/hour or more if well trained |
For long-distance cycling and other endurance events, 60–90 g of carbohydrate per hour is a useful evidence-based target. Some well-trained athletes can work towards 100–120 g/hour, particularly during long, high-intensity events. However, higher carbohydrate intake needs to be practiced during training.
Simply consuming 120 g/hour on race day is a recipe for gastrointestinal problems if your gut is not prepared.
Why can't we simply absorb unlimited carbohydrates?
Your intestine has specific transporters that move different carbohydrates from the gut into the bloodstream.
One of the main pathways for glucose is SGLT1—the sodium-glucose linked transporter 1. When consuming glucose or glucose-based carbohydrates, SGLT1 plays a major role in transporting glucose across the intestinal wall. Traditionally, the capacity of this pathway has been associated with approximately 60 g of carbohydrate per hour during exercise.
This doesn't mean that exactly 60 g/hour is an absolute physiological limit for every athlete. Rather, it illustrates why relying exclusively on glucose can limit carbohydrate absorption and oxidation at higher intakes. This is where fructose becomes particularly interesting.
Glucose and fructose: SGLT1 and GLUT5
Fructose uses a different intestinal transporter called GLUT5.
Because glucose and fructose use different transport pathways, consuming them together allows us to increase carbohydrate delivery without relying exclusively on the SGLT1 pathway.
This is known as multiple-transportable carbohydrate.
A classic endurance fueling strategy is
~60 g glucose + ~30 g fructose = ~90 g carbohydrate/hour
Research has shown that combining glucose and fructose can increase exogenous carbohydrate oxidation compared with consuming glucose alone. More recent research has investigated ratios around 1:0.8 glucose to fructose, which can allow some athletes to tolerate carbohydrate intakes approaching 90–120 g/hour.
However, the goal should not automatically be to consume 120 g/hour. More is not always better.
Your carbohydrate intake should match the duration, intensity, and demands of the event, as well as your individual tolerance.
Can you train your gut to absorb more carbohydrate?
Yes—gut training is an important part of endurance nutrition.
Your gastrointestinal system can adapt to regular carbohydrate consumption during exercise. Repeatedly practicing race fueling can improve your ability to tolerate and absorb larger amounts of carbohydrate. This is particularly relevant when increasing fructose intake and using the GLUT5 pathway.
Think of it in the same way as physical training. You wouldn't expect to increase your FTP dramatically overnight. Your gut also needs progressive exposure.
For example, an athlete might progress from
50–60 g/hour → 70–80 g/hour → 90 g/hour → 100–120 g/hour
The progression should be gradual and based on individual tolerance. This is why gut training should be part of your cycling nutrition strategy, rather than something you only think about during competition.
What should you eat on the bike?
When cycling, the easiest approach is usually to combine different carbohydrate sources so that you are supplying both glucose and fructose.
Glucose-based carbohydrate sources
Maltodextrin
Dextrose
Glucose
Many sports drinks
Some energy gels
Rice
Rice cakes
Bread
Some low-fiber carbohydrate bars
Fructose-containing carbohydrate sources
Fructose
Honey
Bananas
Dates
Raisins
Dried mango
Fruit purées
Some energy gels and sports drinks
You don't need to calculate exactly how many grams of glucose and fructose are coming from every individual food. Instead, look at your total carbohydrate intake per hour and use a mixture of carbohydrate sources.
Example: 90 g of carbs per hour during training
A cyclist targeting approximately 90 g carbohydrate/hour could use:
Carbohydrate drink: 30 g
Energy gel: 25 g
Banana: 20–25 g
Small serving of dried fruit: 10–15 g
This gives approximately 85–95 g/hour.
There are many ways to achieve the same target. You might use gels and drink mix during a race, while during a long training ride you could use more real food such as bananas, rice cakes or dried fruit.
The best fueling strategy is the one that provides enough carbohydrate and that you can actually tolerate for the duration of the event.
When should you start fueling on the bike?
Don't wait until you feel hungry!
By the time you feel completely depleted, it can be difficult to catch up. Instead, start consuming carbohydrate early in the ride, often within the first 20–30 minutes, and continue taking it consistently throughout the event. For example, rather than consuming 90 g of carbohydrate in one large dose, you could divide it into smaller amounts every 15–20 minutes. This can make high carbohydrate intakes easier to tolerate and helps maintain a consistent supply of carbohydrate throughout the event.
Fueling for high-intensity endurance events
Carbohydrate becomes particularly important as exercise intensity increases. During easy endurance riding, your body can rely more heavily on fat oxidation. As intensity increases, carbohydrate becomes increasingly important because it can provide energy at a much faster rate.
This is particularly relevant for:
Cycling races
Gran fondos
Long-distance running
Trail running
Marathon
Triathlon
Road races
Gravel races
Mountain bike events
Long-time trials
A five-hour endurance ride with repeated climbs, attacks, and surges requires a very different fueling strategy from an easy five-hour Zone 2 ride.
Your carbohydrate target should therefore reflect the demands of the event—not simply its duration.
Lactate gels: a new source of fuel?
A newer development in endurance nutrition is the use of lactate-based gels. Lactate has traditionally been described as a waste product of high-intensity exercise, but we now know that this is an oversimplification. Lactate is an important metabolic fuel and intermediate that can be transported between tissues and oxidized by working muscles. This has led to interest in supplying lactate externally during exercise.
Early research suggests that exogenous lactate can be taken up and oxidized, potentially providing an additional fuel source during exercise. This is particularly interesting for high-intensity endurance sports where rapid energy availability is important. However, lactate gels are still an emerging area of sports nutrition research. They should not currently be considered a replacement for established glucose + fructose fueling strategies.
More research is needed to determine the optimal dose and timing and whether lactate supplementation provides a meaningful performance advantage during real-world endurance events.
The future of endurance fueling may therefore involve more than simply asking:
"How many grams of carbohydrate can I absorb?" It may also involve understanding which fuels can be supplied to the working muscles and how they interact with the body's existing energy systems.
The most important endurance fueling rules
If you want to improve your cycling nutrition or endurance fueling strategy, remember these principles:
1. Fuel according to the event. Longer and harder events generally require more carbohydrates.
2. Start early. Don't wait until you are hungry or fatigued.
3. Use multiple carbohydrate sources. Combining glucose and fructose allows you to take advantage of different intestinal transport pathways.
4. Train your gut. Gradually practise higher carbohydrate intakes during training.
5. Don't chase numbers blindly. 90–120 g/hour isn't automatically better if you cannot tolerate it.
6. Practice your race nutrition. Your race fueling strategy should be tested repeatedly before competition.
Frequently Asked Questions
How many carbs should I consume per hour when cycling?
For rides lasting 1–2 hours, 30–60 g/hour may be appropriate. For longer endurance events, 60–90 g/hour is a useful target, while well-trained athletes may work towards 90–120 g/hour.
What is the difference between SGLT1 and GLUT5?
SGLT1 primarily transports glucose, while GLUT5 transports fructose across the intestinal wall. Using both pathways allows athletes to absorb and oxidize more carbohydrate than relying predominantly on a single carbohydrate source.
Can you train your gut to absorb more carbohydrates?
Yes. Regularly consuming carbohydrate during training can improve gastrointestinal tolerance and the body's ability to handle higher carbohydrate intakes. This is known as gut training.
Is 90 g of carbohydrate per hour too much?
Not necessarily. Around 90 g/hour is commonly used during prolonged endurance events, particularly when glucose and fructose are combined. However, athletes should build towards this intake progressively.
What are the best foods for fueling on the bike?
Sports drinks, gels, bananas, rice cakes, dried fruit and other easily digested carbohydrate foods can all be useful. For higher carbohydrate targets, combining glucose- and fructose-containing sources is particularly effective.
The bottom line
Effective endurance fueling is about much more than simply eating more.
Understanding SGLT1, GLUT5, glucose, fructose, and gut training allows you to build a strategy that delivers carbohydrate efficiently throughout a long event.
For many endurance athletes, 60–90 g of carbohydrate per hour is an excellent starting point, with higher intakes of 90–120 g/hour possible after appropriate gut training.
Scientific sources
Jeukendrup AE. A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise. Sports Medicine, 2014.
Jeukendrup AE. Carbohydrate Feeding During Exercise. European Journal of Sport Science, 2008.
Wilson PB. Multiple Transportable Carbohydrates During Exercise: Current Limitations and Directions for Future Research. Journal of Strength and Conditioning Research, 2015.
Stellingwerff T, Cox GR. Systematic review and meta-analysis of carbohydrate supplementation and endurance performance.
Rowlands DS et al. Research on glucose-fructose combinations and carbohydrate oxidation during exercise.
Current research on exogenous lactate metabolism and lactate supplementation in exercise.
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