How Do Carbohydrates Fuel Endurance Performance?

22nd Sep 2026

Carbohydrates are the primary fuel source for moderate to high-intensity endurance exercise. During prolonged activity, the body draws on carbohydrate stores to maintain energy output and delay fatigue. For most endurance athletes, consuming approximately 30 to 60 g of carbohydrate per hour covers sessions lasting one to 2.5 hours. Events exceeding two to three hours often require up to 120 g per hour, sourced from multiple carbohydrate types to access more than one intestinal absorption pathway.

Key Takeaways

Carbohydrate needs increase with exercise duration and intensity, matching intake to the demands of your specific event.
Approximately 30 to 60 g per hour is a widely used starting range for sessions lasting one to 2.5 hours.
Consuming up to 120 g per hour during longer events generally requires a combination of glucose-based and fructose-based carbohydrates, see multiple transportable carbohydrate products.
Glucose and maltodextrin both use the SGLT1 intestinal transporter; fructose primarily uses GLUT5. Using both together allows higher absorption rates.
SiS GO Isotonic Energy Gel provides 22 g of carbohydrate per serving; SiS BETA FUEL Gel provides 40 g in a 1:0.8 maltodextrin-to-fructose ratio.
Test your complete carbohydrate and hydration strategy during training before race day.
Science in Sport states that its Australian products are Informed Sport registered; verify the exact product and batch before use. See health, safety and TGA compliance for further information.

How Do Carbohydrates Support Endurance Performance?

Carbohydrates maintain fuel availability during moderate to high-intensity exercise by supplying glucose to working muscles and the central nervous system. Without sufficient carbohydrate intake during prolonged activity, muscle glycogen stores decline and performance suffers.

As a practical starting point for planning: during sustained high-intensity sessions under 75 minutes, small amounts of carbohydrate or a carbohydrate mouth rinse may offer a modest benefit. For sessions lasting one to 2.5 hours, approximately 30 to 60 g per hour is a commonly used target. The SiS GO Isotonic Energy Gel at 22 g per serving fits easily within this range. During events exceeding two to three hours, up to approximately 120 g per hour from multiple carbohydrate sources is often recommended.

These figures are general guidance, not fixed requirements. Event duration, exercise intensity, body size, starting nutrition status, gastrointestinal tolerance and the overall fuelling plan should all inform individual intake.

How Much Carbohydrate Do Endurance Athletes Need Per Hour?

The amount of carbohydrate an endurance athlete needs per hour depends primarily on exercise duration and intensity. Widely used sports nutrition guidance provides these starting ranges: small amounts or a carbohydrate mouth rinse for high-intensity efforts under 75 minutes; 30 to 60 g per hour for sessions lasting one to 2.5 hours; and up to approximately 120 g per hour for events lasting more than two to three hours. The Australian Institute of Sport (AIS) Sports Supplement Framework supports the use of multiple transportable carbohydrates at higher intake levels to help maximise absorption during prolonged events.

For events longer than three hours, some athletes and competition protocols now target more than 120 g per hour. Evidence for these ultra-high intake strategies is still developing. Athletes considering them should build intake gradually across multiple training sessions and seek guidance from an Accredited Sports Dietitian. Find a dietitian via Sports Dietitians Australia.

How Are Glucose, Fructose and Maltodextrin Different?

Glucose, fructose and maltodextrin each provide carbohydrate but are absorbed through different pathways.

Glucose is absorbed primarily through the sodium-glucose linked transporter 1, known as SGLT1, in the small intestine. Maltodextrin is a starch-derived carbohydrate made from linked glucose units; digestion breaks the chains down into glucose, which is then absorbed via SGLT1. Fructose is absorbed primarily through a separate intestinal transporter, GLUT5.

Because SGLT1 has a maximum absorption rate, consuming glucose or maltodextrin alone limits how much carbohydrate can be absorbed per hour. Using fructose alongside glucose-based sources engages a second transport pathway. Science in Sport's BETA FUEL is formulated on this principle.

Why Combine Maltodextrin or Glucose With Fructose?

Combining glucose-based and fructose-based carbohydrates becomes most relevant when an athlete is targeting more than approximately 60 g of carbohydrate per hour.

At higher intake levels, the oxidation rate of glucose-based carbohydrate alone eventually plateaus. Adding fructose allows the digestive system to use an additional absorption pathway, which may increase total carbohydrate availability compared with a large glucose-only intake. The AIS describes products using this approach as "multiple transportable carbohydrates."

Neither a specific ratio nor a particular product is automatically suitable for every athlete. Total carbohydrate intake, serving frequency, hydration, exercise intensity and individual gastrointestinal tolerance all influence how well a strategy performs. For a personalised fuelling plan, speak with an Accredited Sports Dietitian via Sports Dietitians Australia.

Why Is Maltodextrin Used in Sports Nutrition Products?

Maltodextrin is widely used in sports nutrition gels, drinks and powders because it allows a concentrated amount of carbohydrate to be delivered in a compact, lower-osmolality format. You can find maltodextrin-based options across the SiS energy gel range.

Its presence in a product does not guarantee freedom from gastrointestinal symptoms. Comfort during exercise depends on total carbohydrate intake, product concentration, fluid intake, exercise intensity, environmental conditions and individual tolerance. Test any maltodextrin-containing product during training before using it in an important event.

How Do SiS Energy Gels Fit Into a Carbohydrate Plan?

Science in Sport offers two core gel formats with different carbohydrate amounts and compositions, designed for different points in an event fuelling strategy. Browse the full SiS gel range and choose based on your hourly carbohydrate target, event duration and tested digestive tolerance.

SiS GO Isotonic Energy Gel

Each SiS GO Isotonic Energy Gel delivers 22 g of carbohydrate sourced from maltodextrin. The gel is formulated for isotonic delivery, meaning it is designed to be consumed without additional water, although a separate hydration plan appropriate to your exercise conditions remains important.

As a practical example: two gels consumed across one hour provide 44 g of carbohydrate. Any carbohydrate provided by drinks, chews or food consumed during the same period must be counted toward the hourly total. See the SiS hydration range for compatible options.

SiS BETA FUEL Gel

Each SiS BETA FUEL Gel delivers 40 g of carbohydrate from maltodextrin and fructose in a 1:0.8 ratio. Science in Sport positions BETA FUEL for endurance exercise lasting more than two hours, where higher carbohydrate targets and dual-source delivery become most relevant. Explore the full BETA FUEL system including gels, powders and chews.

The Science in Sport Australia product page recommends a target intake of 80 to 120 g per hour using BETA FUEL. Because intake above approximately 120 g per hour represents an emerging high-carbohydrate strategy, athletes should build toward this range gradually and consider guidance from an Accredited Sports Dietitian before adopting it as a race-day approach.

How Should You Build a Race-Day Carbohydrate Plan?

A reliable race-day carbohydrate plan starts with a target matched to your event duration and intensity, then is tested in training under realistic conditions before the event.

Set an initial hourly carbohydrate target based on your event duration and intensity.
List every carbohydrate source you plan to use: gels, drinks, chews, food.
Calculate the carbohydrate contribution from each source and confirm the hourly total.
Divide servings into regular intervals; consuming 20 to 30 g every 30 minutes delivers approximately 40 to 60 g per hour and is often easier to tolerate than larger, infrequent amounts.
Test the complete plan during training at a similar intensity and in similar environmental conditions.
Record your energy levels, fluid intake and any gastrointestinal symptoms.
Adjust one variable at a time between sessions until you find what works reliably.

Practising your fuelling plan in training is the most important step in building confidence and identifying tolerance issues before they matter.

What Should Athletes Know About Informed Sport Batch Testing?

Science in Sport is Informed Sport certified, with every product batch independently screened through the programme. This third-party certification programme uses LGC’s anti-doping laboratory to test products for substances prohibited in sport under World Anti-Doping Agency (WADA) standards. .

Batch certification reduces supplement risk but does not eliminate it entirely. Sport Integrity Australia advises that no certification programme can provide a complete guarantee against a positive anti-doping test. Competitive athletes subject to anti-doping rules should verify the product and specific batch in the Sport Integrity Australia app before use, regardless of certification status.

Build Your Endurance Fuelling Plan

Choose carbohydrate products matched to your event duration, hourly target and tested tolerance. Precision in training builds confidence on race day.

Frequently Asked Questions

1. What are the best carbohydrates to eat before an endurance race?

Choose familiar carbohydrate-rich foods that you have already tested during training and that sit comfortably before exercise. Common options include bread, rice, pasta, oats and fruit. For a sports nutrition option, the SiS GO Isotonic Energy Gel is an easy-to-digest format some athletes include in their pre-race routine. Test your pre-event meal in training at a similar intensity before relying on it on race day.

2. How can I reduce gastrointestinal discomfort during a long endurance event?

Start with a carbohydrate intake you already tolerate and increase it gradually across multiple training sessions. Use the same products, serving sizes and timing you plan to use on race day. Heat, exercise intensity, fluid intake, pre-race nerves and concentrated carbohydrate products can all increase the likelihood of symptoms. If gastrointestinal problems persist despite adjustments, consult an Accredited Sports Dietitian via Sports Dietitians Australia.

3. Can I take carbohydrates every 30 minutes during an endurance event?

Yes, a 30-minute interval is a practical and widely used distribution strategy. Consuming 20 to 30 g every 30 minutes supplies approximately 40 to 60 g per hour. The SiS GO Isotonic Energy Gel at 22 g per serving fits this interval well. Check the nutrition information panel of each product and account for carbohydrate from all sources to track your hourly total accurately.

4. Why are glucose and fructose combined in endurance gels?

Glucose and fructose are absorbed via different primary intestinal transporters: SGLT1 for glucose and GLUT5 for fructose. Using both together allows the digestive system to draw on more than one absorption pathway simultaneously. The SiS BETA FUEL Gel is formulated on a 1:0.8 maltodextrin-to-fructose ratio to apply this principle at higher carbohydrate intakes.

5. Is maltodextrin appropriate for endurance athletes?

Maltodextrin is a commonly used carbohydrate source in sports gels, drinks and powders and is suitable for many endurance athletes within a planned fuelling strategy. Individual digestive tolerance varies. Check the ingredient and allergen information on any product label, test during training before race day and seek guidance from an Accredited Sports Dietitian for specific dietary requirements or medical conditions.