Targeting your Race Carb Goals [in 2 Simple Steps]

Carbohydrates are making a comeback in endurance sports. Top athletes, such as David Roche and Tour de France winner Tadej Pogačar, have been observed consuming substantial amounts of carbs taking in as much as 120–150 grams per hour. While this may sound extreme, research indicates that consuming sufficient carbohydrates during prolonged events can significantly enhance performance.

Let's break it down so you can figure out your race carb goals as well as the right amount of carbs for training.

What Are Carbohydrates?

Carbohydrates (or "carbs") are your body's primary source of energy during exercise. 

There are three main types:

• Simple carbs: These are sugars like glucose, fructose, and sucrose. They are quickly absorbed and utilized for rapid energy — ideal for endurance sports.
• Complex carbs: Found in foods like grains, vegetables, and legumes, these take longer to digest. Your body eventually breaks them down into simple sugars.
• Fibre: Important for health, but not used directly for energy during exercise.

For endurance events, simple and complex carbs are most relevant, with a focus on simple sugars during training and races.

Scientific note: Carbohydrates provide 4 kcal per gram and are the preferred fuel during high-intensity exercise (Jeukendrup, 2010; Burke et al., 2011).

 

Why You Need Carbs in Endurance Sports

When you exercise, especially for extended periods (e.g., over 60–90 minutes), your muscles use stored carbohydrates (called glycogen). Eating carbs during exercise helps maintain blood sugar, prevents fatigue, and allows you to perform at your best.

If you don't get enough carbs, you might finish your workout, but you'll likely feel sluggish and won't be able to hit top speeds or high efforts.

Scientific reference: Without carbohydrate intake, muscle glycogen depletion is a major cause of fatigue during prolonged exercise (Cermak & van Loon, 2013).

 

How to Target Your Race Carb Goals

Step 1: 

How long and hard are you going?

• < 1 hour: No extra carbs needed.
• 1–2.5 hours: Aim for 30–60 grams of carbs per hour.
• 2.5+ hours: You can benefit from up to 90 grams per hour. The level you choose depends on experience, tolerance and the duration of the event. Many recreational athletes will be comfortable with a 60 g/hour fueling level.
• Advanced athletes in ultra events sometimes push this to 120+ grams per hour, but this should be tested in training first.
• For most people:
  • Choose 60 g carbs or less if exercising 2.5 hours or less.
  • Consider 70-90 g/hour if exercising with at least moderate intensity for more than 2.5 hours.

Scientific note: Jeukendrup (2014) showed that carb intake during prolonged endurance exercise can improve performance, especially above 60 g/hour.

What does 70 g per hour look like?:

1 Mangoes Huma Gel + 1/2 Berry Tailwind Pack + 1/2 Blueberry Pomegranate Gu Chews

Step 2: 

What type of products to choose?

 

1. Know that Different Sugars Matter (Glucose vs. Fructose)

Your body absorbs glucose and fructose using different transport systems in your gut:

• Glucose uses the SGLT-1 transporter.
• Fructose uses the GLUT-5 transporter.

Your body can maximally absorb about 60-70 grams/hour of glucose. If you try to take in more glucose than that, it's like the sugar is a commuter stuck on a subway platform at rush hour- ready to go to work but not enough room to squeeze in and get there. Adding fructose allows you to use a different transporter, kind of like adding another subway line, which enables you to absorb more carbs. That's why combining the two helps you absorb more total carbs.

2. Figure out What Ratio Fits

You may have heard about glucose-to-fructose ratios, but you're unsure what they mean or how to choose products. Know that most carbohydrate products contain a combination of both glucose and fructose, and for most people, you don't need to calculate this ratio in detail.

The glucose-to-fructose ratio compares the amount of glucose in a product to the amount of fructose. For example, a product that has a 1:1 ratio has equal amounts of both sugars. 

When targeting 60 g/hour of carbs, you can meet this goal with glucose alone. Higher targets require the addition of fructose.

A glucose-to-fructose ratio of 2:1 works well up to 90 g/hour. At levels greater than 90 g/hour, ratios of 1:1 or 1:1.08 should be targeted.

Winning Strategy

• 30-60 g/hour target
  • Any combination of carb-based products will work.
  • Select products based on your preferences and tolerance.
• 60-90 g/hour target
  • Choose products mindfully, but many commercial products will work.
  • Choose products that contain a mix of glucose and fructose. A ratio of 2:1 works for this level.
  • Start with >60–70g of glucose per hour, then add fructose to reach your target.
    • For example, to hit >90 g/hour, you can take:
    • 60g glucose + 30g fructose (2:1 ratio).
  • Always test your fueling strategy in training. Everyone's gut tolerance is different.
• >90 g/hour target
  • Specifically choose products with higher levels of fructose.
  • Choose products that contain a 1:0.8 ratio or a 1:1 ratio of glucose to fructose.

Scientific note: Studies show that combining glucose and fructose leads to faster absorption, higher oxidation rates, and less stomach discomfort than glucose alone (Jentjens & Jeukendrup, 2005; Rowlands et al., 2005).

Examples of Glucose + Fructose Ratios

These are examples of commonly used products and their glucose:fructose ratios.

Commercial Products

 

Maurten 100 Gel

1:0.8

 

SIS Beta Fuel

1:0.8

GU Energy Gel

2:1

Krono Energy Gel

1:0.8

 

Food Products

Many ultra athletes like to eat other foods during their events. Here are some examples of common food products and their ratios.

 

Takeaway

Carbohydrates are essential for endurance performance. Whether you're running a marathon or racing a bike for hours, getting the right amount- and the right mix- of carbs can help you go harder, longer, and feel better doing it.

 

Looking for more information on race day nutrition? See this article on our sister site, Gazelle Nutrition, for more on race day nutrition.

 

References

1. Jeukendrup, A. E. (2010). Carbohydrate and exercise performance: the role of multiple transportable carbohydrates. Current Opinion in Clinical Nutrition & Metabolic Care, 13(4), 452–457.
2. Burke, L. M., Hawley, J. A., Wong, S. H. S., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29(sup1), S17–S27.
3. Cermak, N. M., & van Loon, L. J. C. (2013). The use of carbohydrates during exercise as an ergogenic aid. Sports Medicine, 43(11), 1139–1155.
4. Jentjens, R. L., & Jeukendrup, A. E. (2005). High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise. British Journal of Nutrition, 93(4), 485–492.
5. Rowlands, D. S., et al. (2005). Glucose–fructose combination improves endurance performance and carbohydrate use during exercise. International Journal of Sport Nutrition and Exercise Metabolism, 15(4), 386–399.

 

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Written by: Ashley Leone, RD, MSc, IOC. Dipl. Sport Nutr

Ashley is a sports and performance dietitian and the Founder of Fuel Kit and the Owner of Gazelle Nutrition Lab. Ashley has been a dietitian for over 25 years and holds a Master of Science degree from the University of Toronto, as well as a Diploma in Sports Nutrition from the International Olympic Committee.