Nutrition During Runs: How Marathon Runners Fuel, and How You Can Too

Stand on the side of a marathon course at 35 km and you see the real race. Faces tighten. Stride shortens. Some runners slow sharply, others keep moving with almost boring consistency. The difference is rarely bravery or talent. More often, it is fuel.

Marathon runners do not rely on motivation to carry them through the final third of a race. They rely on carbohydrates taken on during the run, usually in liquid or semi-liquid form, at regular intervals. This is not a professional trick. It is basic endurance physiology. And it is something recreational runners can apply just as effectively with the right approach.

This is a practical guide to nutrition during runs. Why marathon runners drink carbohydrates, how much they typically take in, and how amateur runners can achieve the same effect using simple, widely available products.

Why your stored energy is not enough for long runs

Your muscles store carbohydrates as glycogen. Even when those stores are topped up, they are finite. For most runners, glycogen alone supports somewhere between 90 minutes and two hours of steady running before levels fall enough to compromise pace and coordination.

When glycogen drops, the body is forced to rely more heavily on fat. Fat can fuel movement, but not at marathon pace. Effort rises, form deteriorates, and decision-making becomes sloppy. This is what runners experience as “the wall”.

Taking carbohydrates during a run slows this process. You are not replacing all the energy you burn. You are reducing how quickly your limited stores are drained. That delay is often the difference between holding pace and bleeding minutes in the final miles.

How marathon runners actually fuel during races

Modern marathon fuelling is far more structured than it used to be. Instead of a single gel taken reactively, many runners now fuel proactively from early in the race.

A common intake range looks like this:

• 40 to 60 g of carbohydrate per hour for most recreational marathon runners
• Up to 90 g per hour for highly trained runners who have practised gut tolerance

This intake is spread evenly across the hour, usually every 15 to 25 minutes. The goal is steady availability, not spikes. Runners who fuel this way tend to experience fewer dramatic drops in pace late in the race.

Why carbohydrate drinks and gels work better than food

During sustained running, digestion is compromised. Blood is prioritised to muscles and skin, not the stomach. Solid foods require more processing and sit in the gut longer, increasing the risk of bloating and nausea.

Liquids and gels bypass much of this problem. Carbohydrates dissolved in fluid leave the stomach more quickly and are absorbed more predictably. This is why marathon runners overwhelmingly “drink carbs” rather than eat them.

The aim is not comfort in isolation. It is reliable absorption under stress.

How amateur runners can fuel like marathon runners

You do not need access to elite-only products to fuel effectively. The same carbohydrate formats used in marathons are widely available and affordable.

Carbohydrate drink powders

Drink mixes allow runners to spread carbohydrate intake across multiple small sips, which many find easier on the stomach than relying on gels alone.

Look for powders that provide roughly 30 to 40 g of carbohydrate per serving and include sodium to support fluid absorption.

Carbohydrate Drink Powders for Running on Amazon

Drink strength can be adjusted based on conditions. In hot weather, slightly weaker mixes often improve tolerance while still contributing useful energy.

Energy gels for precise fuelling

Energy gels are compact and predictable. Most provide around 20 to 25 g of carbohydrate, making it easy to plan intake across an hour.

They are best taken with water to aid absorption and reduce stomach irritation.

Energy Gels for Running and Marathon Training

Many runners use gels as the backbone of race fuelling, topping up with drinks when possible.

Energy chews as an alternative option

Some runners struggle with the texture of gels. Energy chews offer a similar carbohydrate profile in a form that feels closer to food.

Energy Chews for Endurance Running

Chews tend to work best at steadier intensities where breathing is controlled enough to chew safely.

How to structure fuelling during long runs and races

The biggest mistake runners make is waiting until they feel tired. By that point, the deficit is already there.

A simple, repeatable structure works well for most long runs and marathons:

• Begin fuelling around 20 to 30 minutes into the run
• Aim for 20 to 25 g of carbohydrate every 20 to 25 minutes
• Combine drinks and gels to avoid flavour fatigue

This approach should be practised in training. Long runs are not just about building endurance. They are where you train your gut to tolerate fuel at effort.

If you are following a structured programme from the Running Plan Generator, long runs provide natural opportunities to rehearse race-day nutrition.

Common fuelling mistakes that cost runners time

Under-fuelling is by far the most common issue. Many runners are cautious early on, then pay for it later.

Another mistake is introducing new products on race day. Even well-formulated fuel needs to be tested at pace.

Finally, fuelling without considering pacing often leads to disappointment. Nutrition supports performance, but it cannot rescue aggressive early pacing. Tools like the Negative Split Calculator help runners see how steady pacing and fuelling work together.

FAQs about nutrition during runs

Do I need carbohydrates on runs shorter than an hour?

Generally no, provided the run is easy to moderate. Carbohydrates become more relevant as duration or intensity increases.

Can I fuel only with sports drinks?

Yes, if the drink provides enough carbohydrate. The limiting factor is often how much fluid you can comfortably carry or access.

What if fuelling upsets my stomach?

Reduce the dose, increase frequency, or dilute drinks slightly. Practising during training is essential.

Is fuelling just for races?

No. Long training runs are where fuelling habits are built. Race day should feel familiar, not experimental.

Marathon runners drink carbohydrates because endurance demands it. When amateurs fuel deliberately, long runs become more controlled, pacing becomes steadier, and late-race survival turns into late-race execution.