How Many Carbohydrates Do Athletes Need Per Hour?

When we talk about training, most runners think about mileage, pace, elevation, workouts… but very few think about something that can make the difference between finishing strong or crawling to the finish line: fueling and hydration during the effort.

It doesn’t matter if you’re a recreational runner, preparing for your first 5K, a half marathon, or you have an ultra on the calendar — this is something you need to understand. Knowing how to fuel while you run is a basic skill every athlete should have, even if you later decide not to apply it to the highest level.

Here’s the key point: not all races require the same nutrition strategy.

Running a 10K in 45 minutes is not the same as spending 4 hours in a marathon or 8–12 hours in the mountains. And this is where a skill that many runners ignore comes in: training the gut.

Yes — just like you train your legs, your cardiovascular system, and your strength, you can (and should) train your ability to absorb carbohydrates while running. This not only improves performance, it also dramatically reduces the risk of gastrointestinal issues on race day.

In the world of endurance sports nutrition, one of the most respected references is Precision Fuel & Hydration. In recent years they’ve conducted very interesting analysis and testing to develop high-quality nutrition products.

In this article, we’re using as a reference their blog post written by sports scientist Andy Blow titled How many carbohydrates do athletes need per hour?

In that article, Andy clearly explains the recommended carbohydrate intake ranges during prolonged exercise. He also highlights an important assumption behind these recommendations: they assume you start exercise with high glycogen stores, meaning you consumed a carbohydrate-rich meal or snack 2–3 hours before your session or race. The recommendations are built around the goal of optimizing performance.

According to the article:

• For exercise lasting less than 60 minutes, if you start with full glycogen stores, you don’t need to consume additional carbohydrates.
• Once exercise goes beyond 90 minutes, things change. For sessions lasting up to 120 minutes (2 hours), it’s recommended to consume around 30–60 grams of carbohydrates per hour, with higher intensity efforts leaning closer to 60 g/h.
• When exercise exceeds 2 hours, Andy suggests increasing intake up to 90 grams of carbohydrates per hour. Of course, these higher intakes must be tolerated well. The article emphasizes that the higher the intake, the more important it is to practice and train your gut. Consuming these amounts is not something every athlete can do right away — it requires adaptation.

Here’s one of the most interesting takeaways from their work:

According to Precision Fuel & Hydration, body size does not significantly change how many carbohydrates you can absorb per hour.

In other words, from their perspective, a 50 kg athlete and a 90 kg athlete have a fairly similar absorption ceiling, because the limiting factor is the intestine, not the muscle.

So… should everyone eat the same?

This is where the conversation gets interesting.

From a purely physiological standpoint, it makes sense that there is a relatively universal absorption “ceiling.” But when we bring this into the real world of training and racing, there’s another factor we cannot ignore: energy demand.

A 90 kg runner moving at the same pace as a 50 kg runner:

• is moving more mass

• burns more energy per minute

• likely uses more carbohydrates per hour

Because of this, in my own coaching practice, I (Michael Gonzalez) use a working guideline of 0.7 to 1.2 grams of carbohydrates per kilogram of body weight per hour, adjusted based on intensity and the type of session.

This is not about contradicting Precision — it’s about integrating both realities:

• Yes, there is an intestinal absorption limit

• But there is also an individual energy demand

And the athlete’s job is to find the point where both align — where, based on their own sensations and performance, they find the intake that keeps their energy levels high and stable.

The real game changer: train your gut

Regardless of which approach you follow, there is something everyone agrees on:

You cannot improvise your carbohydrate intake on race day. It must be trained.

Your gut adapts just like your muscles do.

If today you tolerate 30–40 g/h, you cannot expect to handle 80–90 g/h overnight.

Progression is key:

• Start with an amount you tolerate well

• Practice during long runs

• Adjust sources, textures, and timing

• Gradually increase your intake

Over time, your ability to absorb and use more energy improves — without discomfort.

And that process, when done correctly, can be the difference between holding your pace in the final hour… or simply surviving.

In summary

Understanding how to fuel and hydrate during exercise is a fundamental skill for every runner.

The work from Precision Fuel & Hydration and Andy Blow provides a strong scientific foundation on absorption limits and general guidelines.

Our approach adds another layer of individualization by considering body weight, intensity, and each athlete’s energy demands.

But both perspectives agree on the essentials:

• train your gut

• practice your fueling in training

• arrive on race day with a clear plan

If you’re preparing for a race and don’t know how much you should eat, what products to use, or how to start training your nutrition, feel free to reach out or leave a comment.

We love helping runners perform better — and enjoy every mile of the process.

You can also read the full article from Precision Fuel & Hydration here: How many carbohydrates do athletes need per hour?

Leer este artículo en Español: ¿Cuántos carbohidratos necesitan los deportistas por hora? análisis del articulo de PRECISION FUEL & HYDRATION