How Many Grams of Carbohydrate per Hour Does an Ultra-Cyclist Need?

To fuel successfully over ultra distance can be a challenge, both for nutritionists who coach ultra-cyclists and for the riders who love distance.

We all know that the further you go, the more complicated it gets.

One of the first things to figure out is a happy carbohydrate place within your overall fuelling system.

This is both an art and a science.

The science of carbohydrate is full of competing ideas. High carbohydrate. Low carbohydrate. No carbohydrate. Multiple forms of carbohydrate. You can find an expert or a body of evidence to support almost every point of view.

The art is figuring out what works and keeps working over distance.

So, how many grams of carbohydrate per hour does an ultra-cyclist need?

The short, and unfulfilling, answer is, it depends.

But for many ultra-cyclists, somewhere in the range of 0.5 – 1.0 gram of carbohydrate per kilogram per hour is a useful place to start.

From there, you can adjust according to intensity, duration, terrain, conditions, metabolic fitness and, perhaps most importantly, what your gut can comfortably handle.

Because what works beautifully for six hours doesn’t necessarily work for twelve, eighteen or twenty-four.

A little ultra nutrition science

Adenosine triphosphate (ATP) is the chemical energy that your cells use to fuel performance.

Muscle fibres need it to contract and produce force, from your heart beating to your hip flexors flexing.

We can’t store much ATP, nor can we eat it in appreciable amounts, so our cells have to constantly produce it, and then break its bonds to release energy.

When you train or race, the demand for ATP increases significantly and rapidly.

When you race over great distances, that demand continues for hours, days, and nights.

So where do the fuels that produce all that ATP come from?

Carbohydrates and fats

The two primary substances our bodies use to produce ATP are carbohydrate, in the form of glucose, and fat, in the form of fatty acids.

Our cells, or more specifically the mitochondria within our cells, constantly adjust the proportion of carbohydrate and fat they use depending on several factors.

Heart rate, intensity, availability of oxygen, training status, terrain and the outside environment all play a part.

One factor that has a profound effect is the immediate availability of carbohydrate.

The more carbohydrate that is available, the greater the likelihood that it will be used to produce ATP.

This is one reason carbohydrate is such an important fuel source for cyclists, and why most riders pack gels, bananas, bars and carbohydrate drinks in their pockets and bottles.

But don’t mistake ‘preferred’ fuel source for ‘singular’ fuel source.

Depending too heavily on carbohydrate for ATP production during ultra-endurance can be a fickle business.

A carbohydrate-dependent ultra-cyclist is more likely to run into gut issues, simply because of the amount of carbohydrate required to sustain performance over very long periods.

In my experience, most guts can handle a surprisingly large amount of carbohydrate for around six to eight hours.

After that, things can start to change.

Undigested and unabsorbed carbohydrate can accumulate and contribute to the collection of symptoms we often describe as a ‘sloshy gut’.

What happens when carbohydrate availability is low?

Conversely, when carbohydrate availability is low, a greater proportion of fat is used to produce ATP.

This is where the body’s ability to use fat as a fuel becomes particularly interesting for ultra-athletes.

Body fat provides a very large reserve of fuel. Being able to access that fuel efficiently reduces our dependence on constantly replacing carbohydrate through food and drink.

This can be particularly useful when you’re riding for many hours, or even days.

But there is a trade-off.

Fat oxidation is generally a slower process and most effective under specific conditions, generally lower intensities.

Unless you’re a highly efficient ultra-athlete with a well-developed ability to use fat as fuel, relying too heavily on fat can mean a reduction in speed and power.Once again, over-dependence on one fuel source can be fickle business

A little ultra nutrition art

I prefer the middle ground.

The middle ground where the ratio of ATP production from fat versus carbohydrate is managed by balancing factors such as fuel availability, fuel type, terrain, intensity and environmental costs.

Think heat, cold, wind and altitude.

This requires metabolic fitness and flexibility.

And, like all things performance, it can be trained.

The goal isn’t to become a fat-burning machine and eliminate carbohydrate.

Nor is it to consume as much carbohydrate as your stomach will accept.

The goal is to develop the ability to use both fuel sources effectively, while providing enough carbohydrate to support the work you’re asking your body to do.

So, how many grams of carbohydrate per hour?

For a long, steady Zone 2 ride, I often start towards the lower end of that range, somewhere around 0.5–0.7g of carbohydrate per kilogram of body weight per hour.

For a 70kg rider, that’s approximately 35–50g of carbohydrate per hour.

That might come from a combination of carbohydrate in a bottle and small amounts of solid food that the rider knows they tolerate well.

But this isn’t a magic number.

The appropriate amount will depend on the rider, the intensity, the duration and the conditions.

A six-hour event at a relatively high intensity is a very different nutritional proposition from a 24-hour ultra where you’re riding through the night.

The amount you can absorb comfortably isn’t necessarily the amount you need to consume.

Your goal is not to match calorie output with calorie input.

First, that’s close to impossible. Second, even if you could calculate it, your gut would simply refuse to process that much food and carbohydrate hour after hour.

Your gut is part of the performance system too.

You need to find the amount of carbohydrate that supports the work without creating a nutritional problem of its own.

Training metabolic fitness

It is possible to train your metabolic fitness – and therefore increase your ability to use fat as a fuel – by deliberately reducing carbohydrate intake during low-intensity training sessions.

For example, carbohydrate intake of around 0.3–0.5g per kilogram per hour while maintaining a steady intensity with good oxygen availability can provide a useful training stimulus.

This will likely be Zone 2, depending on your starting point.

I would especially restrict large amounts of fast-acting carbohydrate, such as the 25-30g found in many gels.

Instead, I would favour small, consistent sips of carbohydrate through bottle mix, with additional small amounts of solid food.

Consistency is key when training metabolic fitness.

The goal is to provide a specific amount of carbohydrate per hour, every hour, while holding a steady pace.

The perfect time to train this is often during the winter months, when the focus is on building base mileage.

Those long, low-heart-rate miles add up, as do metabolic adaptations.

Of course, once you start to intersperse your training with higher-intensity sessions, fuel those sessions accordingly.

And please remember, training low doesn’t mean racing low.

Training low is to encourage metabolic flexibility. When we race, we want to use the full range of that metabolic flexibility and that means fuelling to support performance, while also allowing fat oxidation to reach steady state.

Finding your carbohydrate sweet spot

Ultimately, there is no single carbohydrate number that works for every ultra-cyclist.

The science gives us useful parameters.

Your body gives you feedback.

And experience teaches you how to put the two together.

I want an ultra-cyclist to be able to take on enough carbohydrate to support performance without becoming dependent on carbohydrate for every bit of energy they need.

I also want them to be able to use their fat reserves effectively.

That’s metabolic flexibility.

One last thing

There’s lots more we can do to support metabolic fitness, both on and off the bike.

Your metabolism is a responsive system.

It responds to inputs — food choice, timing, volume, intensity and training load.

The aim isn’t to find one perfect number of grams of carbohydrate per hour and stick to it forever.

It’s to understand your own physiology well enough to know when you need more, when you can use less, and how to keep fuelling effectively when the ride gets really long.

Because in ultra-endurance, it’s not just about what works at hour two.

It’s what still works at hour ten, 20, 60 and beyond.

---

I work with athletes who want to hone their metabolic fitness, and non-athletes who want to develop metabolic fitness and flexibility.

There are numerous ways to work with me. Check out what people have said.