Your marathon is around the corner and you’re wondering how to fuel it properly. This is where fueling goes from “helpful” to non-negotiable. Whether your race is weeks away or just around the corner, this guide is here to give you a clear, easy to understand plan. There are 3 parts: 1. Fuelling your training. 2. The carb load. 3. Race day fuelling. Let’s jump in!
You must practice fuelling in your training. Even though SAP is extremely easy to digest (especially compared to artificial options), your system still needs reps. Your gut and metabolism need to be trained to work alongside your endurance system.
To keep it simple: Plan at least 2+ rehearsals where you fuel as though it’s race day (This includes pre race breakfast). Fuel all runs over 45 to get fuelling reps in and also reduce injury risk.
The legendary carb load. Some fear it, others love it. Do you need to do it? Absolutely yes.
The carb load is the biggest lever you can pull to to make sure you perform on race day and reap the rewards of all those training weeks.
What is a carb load and why?
A carb load is a short period (2–4 days) where you deliberately increase carbohydrate intake to fully top up glycogen stores. Glycogen is your body’s primary and preferred fuel during the marathon. Once it drops too low, your body shifts into backup systems - breaking down muscle, disrupting blood sugar and hormones - aka “the wall.”
Think of your body like a hybrid car: Glycogen = battery, Other fuel sources = old diesel. Electric is smooth, quick, easy. You can run on diesel, but it can be clunky and exhaustive. Either way, you want the battery fully charged before you start.
How much glycogen and energy can you store?
When fully carb loaded: Muscle + Liver: ~480–600g of carbs that is ~2,000–2,400 calories of stored energy. Most runners will burn that many calories or more in a marathon. That means it is critical that you carb load so you get to the start line with enough stores AND you fuel during the race to keep those stores.
5 Days Before the Race
Goal: Start topping up stores and simplify digestion. Isn’t a carb load only 2-3 days? The majority of your carb top up will be - but it is important to start easing into it and simplifying your digestion.
3 Days Before the Race
Goal: Full carb load. Hydration is also important. Track your carb intake! Keep a note of it on your phone or use an app. Most runners overestimate how many carbs they actually eat and fall shy of the 10g/kg target. Example: A 75kg runner equals 750g carbs per day. That’s a lot of pasta.
What to Eat During a Carb Load
The goal isn’t to increase calories significantly. Instead, you want to shift to a high carb, low protein and very low fat diet. You also want to reduce fibre and foods that don’t sit well with you.
What about hydration?
Hydration is critical during a carb load. Carbs are stored alongside water. For every 1g of carbs there is 4g of water. You will notice your weight on the scale go up - but this is only temporary water weight and is what you will use during the race to perform. Welcome it!
The Day Before the Race
Goal: Hitting your carb targets is non-negotiable, time your meals, and get off your feet and horizontal somewhere. It’s easy to want to move around lots especially if you are out of town. That will just burn extra energy.
RACE MORNING
Goal: Final top up but show up to the start line feeling fresh. Breakfast: 3 hours before the race. Aim for 1-2g carbs per kg of bodyweight. Keep fat and fibre to pretty much zero. Protein is very low.
Example: white bread or bagel with SAP or jam. Oats can also work but some people find it heavy. Do what feels good and you have practiced. Snack: 45-60 min before while heading to or waiting for the race to start. Example: Banana, carb bar, SAP
20 min pre race: 1 SAP
Target 50–90g carbs per hour.
The more you can take on the better your system will operate. That said, race day shouldn’t be when you introduce more carbs than you’ve practiced. Practice this in your training. Trust it. Execute.
1 SAP every 30 min = 50g/hr
1 SAP every 20 min = 75g/hr
1 SAP every 17 min = 90g/hr
WHY
You NEED to fuel a marathon because:
• Stored glycogen is not enough on its own
• Liver glycogen will drop
• Blood glucose will fall without input
Fueling during the race:
• Slows glycogen depletion
• Keeps blood glucose stable
• Reduces brain-driven fatigue
• Helps you hold pace especially after 30km
Simple way to think of it like this: You start with a full tank — but the race is long enough that you will drain it unless you keep adding fuel.
POST RACE
Enjoy the celebrations - you’ve earned it! But don’t forget to refuel so you can be a normal human the next day: Carbs to refill the glycogen. Lot’s of protein to repair muscles. Start restoring fat for hormones.