Cycling Endurance Athlete On The Bike Riding Down The Road Practicing Fueling Strategy

Fueling Strategy for Endurance Sports: Combining Glucose and Fructose

BY Dom Kuza

Falling flat in training and racing despite your fueling strategy? Combining glucose and fructose might be your new secret weapon.

Whether you’re a seasoned athlete or just starting, endurance sports demand a lot from your body. One key to improving performance, no matter your level, is understanding how your body utilizes energy sources, particularly carbohydrates. Here, we explore how your body processes carbs, why combining glucose and fructose can optimize energy utilization, and supplementation tips for endurance athletes.

Understanding Carbohydrate Transporters: SGLT1 and GLUT5

Our bodies have specific transporters for absorbing different types of sugars. One main way glucose is absorbed is through the SGLT1 transporter, while fructose utilizes the GLUT5 transporter. When you consume only glucose, the SGLT1 transporters can become saturated, limiting glucose absorption to about 60 grams per hour.

WorldTour cyclists who engage in high-intensity cycling often consume between 100 and 120 grams of carbohydrates per hour. This high intake is due to the intense demands of professional cycling, where maintaining high glucose levels for muscular and cognitive function is crucial. The ability to absorb and utilize such high amounts of carbohydrates is often a result of specialized training and adaptation, allowing their bodies to efficiently process these carbohydrates during high-intensity efforts.

For broader endurance activities, an intake of 60-90 grams per hour should be sufficient for energy demands. The specific intensity that correlates with this range varies based on the sport and the athlete’s conditioning. Generally, this recommendation applies to moderate to high-intensity endurance activities. These activities are typically characterized by sustained effort that is not maximal but still requires a significant and continuous energy output.

Carbohydrate Needs Based on Event Duration

For events lasting 4-5 hours, a higher carbohydrate intake is often necessary to maintain optimal performance. This is because glycogen stores (the body’s stored form of carbohydrates) are limited and can be depleted during such durations of exercise. Athletes might aim for the higher end of the 60-120 grams per hour range, depending on their tolerance and the event’s intensity.

In ultra-endurance events, carbohydrate needs are complex and vary significantly. While high carbohydrate intake is still crucial, the intensity is often lower compared to shorter events, which can affect the rate of carbohydrate utilization. Additionally, gastrointestinal comfort and the ability to consume and digest food become more significant factors over longer durations. Athletes might consume lower rates of carbohydrates per hour compared to shorter events but focus more on continuous and consistent intake to prevent energy dips and maintain endurance.

3 Key Benefits of Mixing Glucose and Fructose

By including fructose, which uses a separate transporter than glucose, you can increase your total carbohydrate absorption, thus enhancing available energy. This mixed intake leads to greater total carbohydrate oxidation than consuming glucose alone. While your glucose transporters may be saturated, fructose can still be absorbed, allowing for additional carbohydrate uptake.

Mixing fructose and glucose offers three key benefits for endurance athletes:

1. Ensures a steady energy supply

Maintaining a high carbohydrate oxidation rate during prolonged exercise is crucial for sustaining high-intensity performance. The combined absorption of glucose and fructose ensures a steady energy supply.

2. Avoids possible GI Issues

Consuming high amounts of glucose alone can lead to gastrointestinal issues. However, using both glucose and fructose minimizes this risk, as fructose absorption doesn’t compete with glucose, thereby reducing gastrointestinal stress. 

3. Conserves Energy

The mix allows the body to maintain energy levels over longer periods, which is essential in endurance sports.

Supplementing Fructose and Glucose: Tips for Athletes

While about 60 grams of glucose can be absorbed per hour, adding fructose further enhances carbohydrate absorption. Ratios of 0.8:1 (fructose to glucose) are considered more beneficial for absorption. Such mixtures allow for higher carbohydrate intake with a lower onset of gastrointestinal discomfort, which is critical in both high-intensity and long-duration activities.

Maximize your carbohydrate absorption during those long runs, rides, and/or swims by properly supplementing fructose and glucose: 

  1. Start with a 0.8:1 fructose-to-glucose ratio and adjust based on your personal tolerance and performance needs.
  2. Gradually increase your carbohydrate intake during training to adapt your digestive system.
  3. Always pair your carbohydrate intake with adequate hydration and sodium to facilitate absorption and reduce gastrointestinal discomfort.
  4. Practice your fueling strategy during training sessions to mimic race conditions.

If you’re struggling to find the perfect fructose/glucose concoction, consider giving RAW Nutrition’s endurance product, FUEL, a try. This new formula combines the perfect ratio of 0.8:1 (fructose to glucose) with 24g carbohydrates and 300 mg sodium per serving size, providing you with the optimal balance of sodium and carbohydrates.

Understanding how your body absorbs and utilizes carbohydrates can significantly impact your performance. Strategically combining glucose and fructose will enhance your energy levels, maintain high-intensity performance for longer durations, and minimize the risk of gastrointestinal distress. (Goodbye belly aches, hello new personal best!)


Beelen, M., et al. (2015). Performance enhancement by carbohydrate intake during sport: effects of carbohydrates during and after high-intensity exercise. Retrieved from

Jeukendrup, A. (2014, May). A step towards personalized sports nutrition: Carbohydrate intake during exercise. Retrieved from

Rowlands, D., et al. (2015, November). Fructose-Glucose Composite Carbohydrates and Endurance Performance: Critical Review and Future Perspectives. Retrieved from

Urdampilleta, A. et al. (2020, July). Effects of 120 vs. 60 and 90 g/h Carbohydrate Intake during a Trail Marathon on Neuromuscular Function and High-Intensity Run Capacity Recovery. Retrieved from

Viribay, A. et al. (2020, May 11). Effects of 120 g/h of carbohydrates intake during a mountain marathon on exercise-induced muscle damage in elite runners. Retrieved from

Trainingpeaks Premium App

Train Smarter With Premium

Premium App

With TrainingPeaks Premium you can easily analyze workouts, move training around to fit your busy schedule, and track your progress with weekly fitness summaries.

Photo Of Raw Nutrition Brand Educator Dom Kuza
About Dom Kuza

Dominic Kuza, M.S., brings nearly a decade of experience in the fitness industry as a multifaceted professional, performing roles as a coach, educator, and seasoned competitor. He offers coaching services to a diverse clientele, including individuals focused on functional health, bodybuilding, endurance training, and those from the general population. He also serves as the brand educator for RAW Nutrition and Revive MD, contributing to product formulation and development. He completed his Master’s Degree in Exercise Science in 2019, with his elective concentration on human, medical, and exercise physiology.

Related Articles