Carb Loading vs Regular Fuelling: What’s the Difference Before a Marathon?

We talk so much about carb loading before a marathon.

But what’s actually different about a carb load compared with regular fuelling?

If you’re heading towards a marathon, particularly one like Berlin, it’s easy to think that the most important nutrition happens in the final few days.

But your marathon fuelling doesn’t start with your carb load.

It starts with how you fuel your training block.

Regular fuelling vs carb loading

Throughout your training block, you might be running the same distances as race day, or shorter distances at a lower intensity.

Race day is different.

You’re going full pelt.

You’re asking your body to run for hours at a high intensity, using large amounts of stored carbohydrate.

And while you’re building towards race day, your training load should eventually decrease as you taper.

That’s where carb loading comes in.

Carb loading isn’t about suddenly trying to fuel all the training you’ve done.

It’s about increasing carbohydrate availability while your training volume decreases, helping you start the marathon with your glycogen stores well stocked.

So what does that actually look like?

These are general sports nutrition ranges, rather than rules that work identically for every athlete.

🥣 During regular training

For moderate training, carbohydrate needs might sit around 5–7g/kg/day, increasing as training volume and intensity increase.

The important part is consistency.

You need enough total energy and carbohydrate to support the training you’re actually doing, rather than trying to make up for it later.

🏃♀️ During longer or harder sessions

For longer or harder training sessions, around 30–60g of carbohydrate per hour is a commonly used starting range, with higher intakes often used for longer endurance efforts.

This is also a chance to practise your race fuelling.

Your long runs are not just about building fitness.

They’re an opportunity to find out:

• What fuel works for you

• How much you can comfortably eat

• How often you want to take it

• What your gut tolerates

• What you actually enjoy eating

• How you want to fuel when you’re tired

Race day is not the time to experiment.

🍝 Carb loading before a marathon

For the final 2–3 days before a marathon, carbohydrate intake may increase to around 8–10g/kg/day, while training volume is significantly reduced.

This is the key difference.

You’re eating more carbohydrate while doing less training.

That gives your body the opportunity to maximise carbohydrate stores before race day.

And remember, carb loading doesn’t mean you need to eat enormous meals.

It’s about deliberately increasing carbohydrate intake across the day using foods and fuels that you know work for you.

🍌 What about race morning?

Carb loading is only one part of the strategy.

You also need to think about your pre-race meal or snack.

A general range is around 1–4g carbohydrate/kg in the 1–4 hours before exercise, depending on the timing, the individual and what they have practised in training.

For an early marathon start, this can be challenging.

You might be waking up at 4 or 5am, travelling to the start, dealing with nerves and not feeling particularly hungry.

That doesn’t mean your body doesn’t need fuel.

It just means you need a plan that works for you.

This is one reason familiar, easy-to-eat foods can be so useful on race morning.

🏃♀️ And then you actually have to run the marathon...

Your carb load gets you to the start line with your carbohydrate stores topped up.

It doesn’t mean you’re fuelled for the entire marathon.

You still need to fuel during the race.

Keep taking on carbohydrate regularly throughout the marathon, using the strategy you have practised during your training.

This is where familiar fuel really matters.

If you’re travelling for a race, you might not be able to find the exact products you normally use.

You might not want to rely on whatever happens to be available at the race expo or at the start.

So take your usual fuel with you from home.

That’s something we hear from so many RED-Scue customers heading away for races.

They pack their RED-Scue bars so they know they have something familiar to eat before, during and after the race.

🥪 And don't forget what happens afterwards

Your fuelling job isn’t finished when you cross the finish line.

Post-race nutrition is about supporting recovery and replacing what you’ve used.

Think:

Carbohydrate + protein + enough overall energy.

You’ve just asked a huge amount from your body.

Recovery is part of the marathon, too.

Why does all of this matter?

Because I see so many athletes get a stress fracture just before their marathon.

Stress fractures are multifactorial. Training load, recovery, bone health, previous injury and nutrition can all play a role.

Low energy availability is one factor that can negatively affect bone health and increase injury risk.

Which is why waiting until carb-loading week to think about nutrition misses a huge part of the picture.

You cannot carb load your way out of months of under-fuelling.

Carb loading has a specific purpose.

Regular fuelling has a different one.

Your training deserves fuel too

Think of your marathon nutrition as a whole process:

Fuel your training block.

Practise your race fuelling.

Carb load as you taper.

Fuel on race day.

Recover afterwards.

There is no magic three-day window where nutrition suddenly becomes important.

Your body has been doing the work for weeks and months before you reach the start line.

So if you’re heading towards Berlin, now is the time to think about your fuelling strategy.

Not just your carb load.

Your breakfast.

Your training fuel.

Your race fuel.

Your recovery.

And the fuel you’re going to pack in your suitcase.

Your carb load is only one part of the picture.

Your training deserves fuel too. ❤️

Where RED-Scue fits in

RED-Scue was created around one simple idea:

food-first fuelling.

Our bars are designed to give athletes a practical source of carbohydrate in a solid, smooth format that’s easy to eat before, during or after training and racing.

And because they’re familiar food-based fuel, they can be particularly useful when you’re travelling and want to take something you already know works for you.

Fuel the sport you love for life.

Fuel Without Fear.