Half Marathon Fuel Guide

You should practice fuelling how you plan to race.

Even though SAP is extremely easy to digest, your metabolic system still needs practice working alongside your endurance system. Get into the habit of fuelling your training runs and plan at least 2 race-day rehearsal workouts were you fuel as though it’s race day. This removes guesswork on race day.

Do I Need to Carb Load?

Short answer: yes. Long answer: perhaps not as aggressively as a marathon.

A carb load is a short period (2–4 days) where you increase carbohydrate intake to fully top up your glycogen stores. Glycogen is your body's primary and preferred fuel source during endurance events. Once that drops too low, it starts tapping into backup systems — breaking down muscle, messing with blood sugar and hormones — aka “the wall.”

Think of your body like a hybrid car: Glycogen = battery. Fat and other fuels = diesel. You want the battery fully charged before the race. 

How much glycogen/carbs are needed? 

Your body can store around 480-600g of carbs in your liver and muscle. This is roughly 2,000-2,400 calories and for most people more than enough to get you through the half-marathon - if fully topped up before. 

You might be doing the math and wondering then - do I need to fully top up my stores if I only burn x amount?

Short answer: yes. While you might not burn through all of your stores during the race, there’s only upsides and no downside to starting a half marathon with full glycogen stores - so we recommend carb load.

How to Carb Load - Simplified for Half Marathon

Avoid heavy, greasy, or unfamiliar foods. Common mistake: people will use pizza or pastries to carb load, but they have lot’s of fat which slows down digestion and can leave you feeling heavy or running to the loo on race day. 



Day Before the Race. Not much changes, except for really dialing in the following:

Common mistake: having a huge dinner before race day which can impact sleep and leave you feeling stuffed. Instead, opt for a big lunch and lighter dinner.

Race Morning

Your final top-up. Aim for 1–2g of carbs per kg of bodyweight, 2–3 hours before the start.
Keep fat, fibre, and protein very low. Examples: White bread or bagel with SAP or jam. Oats with SAP and banana.

HOW TO FUEL RACE DAY

First – Why? You might be thinking - I have carb loaded and my glycogen is full, why do I need to fuel during?  Unless starting depleted, you don’t fuel a half marathon to refill muscle glycogen.
You fuel it to protect blood glucose and the nervous system.

Think of it like this: You start with a full tank, but your dashboard starts flashing early if blood sugar drops - even when the tank isn’t empty. Keeping glycogen topped up makes energy access smoother — helping pace, blood sugar, and hormones stay stable.

Now - How to Fuel 

Stick to what you practiced in training. You got this. 
Aim for 50–90g of carbs per hour, depending on pace and tolerance:
1 SAP every 17 min = 90g/hr
1 SAP every 20 min = 75g/hr

1 SAP every 30 min = 50g/hr

There’s your Half Marathon fuel guide. To wrap it up: 

Fuelling in training =
race day rehearsal 
Pre-race carb load =
biggest performance lever
In-race carbs (30–60 g/hr) = pace insurance