How Much Carbohydrate Can We Tolerate Per Hour Using Energy Gels and other Products for Endurance Performance

Endurance Sports: Fueling Your Performance with Carbohydrates

Endurance sports demand a lot from the body. One key factor that can make or break your performance is how well you fuel yourself during exercise. Carbohydrates are the main energy source for endurance athletes. But how much carbohydrate can you actually tolerate per hour? And how do energy gels fit into this picture? I’ll break down the science and practical tips to help you get the most from your carb intake during long workouts or races.

Close-up view of energy gels and water bottle on a running trail

Why Carbohydrates Matter for Endurance

Carbohydrates are the body’s preferred fuel during moderate to high-intensity exercise. When you run, cycle, or swim for long periods at these intensities, your muscles rely heavily on carbs stored as glycogen and glucose in your blood. Once these stores run low (somewhere around 40-60 minutes), fatigue sets in quickly.

Eating carbs during exercise helps maintain blood sugar levels and delays fatigue. It also supports brain function, which is crucial for focus and motivation during tough sessions. That’s why endurance athletes often consume carbs in the form of drinks, bars, or gels while training or competing.

How Much Carbohydrate Can You Tolerate Per Hour?

The amount of carbohydrate you can absorb and use depends on several factors:

• Your gut’s ability to digest carbs without discomfort

• The type of carbohydrate consumed

• Your training status and adaptation to carb intake

• Exercise intensity and duration

  
  

Research shows most people can absorb about 60 grams of carbohydrate per hour from a single source like glucose or maltodextrin. Going beyond this often causes stomach issues such as bloating, cramps, or nausea.

However, combining different types of carbohydrates can increase absorption rates. For example, glucose and fructose use different transporters in the gut. When taken together (usually a 2:1 or 1:0.8 ratio of maltodextrin to fructose), you can absorb up to 90 grams or more per hour without discomfort. Some highly trained athletes will even get up to approx 120 grams per hour - this is very close to the upper limit of ingestion!

Using Energy Gels to Meet Carb Needs

Energy gels are a popular choice for endurance athletes because they are easy to carry and digest. They typically contain a mix of simple sugars designed for quick absorption.

One example is the GU Energy Gel. It contains 22 grams of carbohydrates per packet, combining maltodextrin and fructose for better absorption. It also includes electrolytes and amino acids to support hydration and muscle function. You can check it out here.

Another option is the SIS GO Isotonic Energy Gel. This gel offers 22 grams of carbohydrate per serving and is designed to be taken without water, making it convenient during races. It uses a blend of glucose and fructose to maximise carb uptake. More details are available here. SIS also do a Beta Fuel version of their gel with 40 grams of carbs per serving.

How to Use Energy Gels Effectively

• Start taking gels early in your session, around 20-30 minutes in. Don't wait until you start to feel 'low' - that's too late!

• Space them out every 20-30 minutes to maintain a steady carb supply. Do your maths to ensure you get the correct amount per hour for you. Log this in your training diary along with any GI distress you suffer, so that you learn and get an optimal amount on race day!

• Drink water with gels unless they are isotonic (like SIS GO), which can be taken alone. If you don't drink water with them, you will potentially dehydrate.

• Practice your gel strategy during training to avoid surprises on race day.

  
  

Practical Carb Intake Guidelines for Endurance

The amount of carbs you actually need will depend on your body mass, fitness level, gender, and the duration of the event you are undertaking. Here's a simple plan based on current sports nutrition guidelines:

• Exercise lasting 1-2.5 hours: 30-60 grams of carbohydrate per hour (less because you have stores already in your liver and muscles)

• Exercise lasting over 2.5 hours: up to 120 grams per hour using multiple carb sources

  
  

For example, if you use GU Energy Gel (22g carbs), taking one every 20-30 minutes plus some sports drink can help you hit your target for short durations. If you prefer SIS GO Isotonic Gel, you can take it every 30 minutes without extra water, which is handy for quick refuelling. For longer efforts, you may need to switch to a gel such as SIS BETA, in order to get the increased amount of carbs.

Training Your Gut to Handle More Carbs

Your gut can adapt to higher carbohydrate intake with practice. Start by adding small amounts of gels or sports drinks during training. Gradually increase the amount and frequency over weeks.

Physiologically, carbohydrate transporters (SGLT 1 for glucose and Glut 5 for fructose) increase in number - meaning more carbs can be transported into cells. We also start to secrete increased levels of amylase - meaning the carbs can be digested quicker. Finally, gastric emptying (of the stomach) will happen quicker, meaning you can eat higher volumes!

Our microbiome changes too and the digestive system becomes more tolerant to high sugar levels. This adaptation reduces the risk of stomach issues.

Eye-level view of a runner taking an energy gel during a long run

Signs You’re Taking Too Much Carbohydrate

Watch out for these symptoms during exercise:

• Stomach cramps or pain

• Bloating or gas

• Nausea or vomiting

• Diarrhoea

  
  

If you experience these, reduce your carb intake or try different products. Sometimes switching to gels with different sugar blends or lowering the amount per hour helps.

Other Tips for Carb Intake Success

• Combine gels with fluids to aid digestion unless using isotonic gels.

• Avoid trying new products on race day.

• Consider your sweat rate and electrolyte needs alongside carbs - remember - you need additional water!

• Use a mix of carb sources (gels, drinks, bars) for variety and better absorption.

  
  

Good luck!

Paul

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This article is for informational purposes only and does not replace professional medical advice.