Is the wall purely nutritional?

No, it's multifactorial: starting pace, training level, effort management and nutrition. But insufficient carb intake is one of the most common and most avoidable causes.

When should I start fuelling?

Within the first half hour, then steadily. Waiting until you're hungry or flat is already too late: the deficit grows faster than you can fill it.

Is carb loading enough to avoid the wall?

It helps by filling your starting stores, but doesn't replace intake during the race. The two work together.

Running8 min

Hitting the wall in the marathon: nutrition and prevention

The marathon 'wall' — the sledgehammer that often hits after the 30 km mark — is largely a fuel story: your glycogen stores run down and, without enough intake, your pace collapses. Nutrition isn't everything — your starting pace, training and effort management matter too — but a well-built carb strategy is your best insurance against an energy crash. Here's how nutrition, before and during, helps push the wall back.

Delaying the wall during the race

The wall hits when muscle and liver glycogen fall too low. To delay it, take carbs steadily from the start: 30 to 60 g per hour for most runners, up to 60-90 g/h for those trained to high intensity and intake. The key is to start early — before you feel flat — and stay regular, a dose every 20 to 30 minutes rather than one big late hit. Above 60 g/h, favour glucose + fructose products to absorb more without overwhelming the gut.

The role of carb loading

In the 2 to 3 days before the marathon, raising the carb share of your diet helps maximise your starting glycogen. On race morning, a final carb meal 3 to 4 hours before tops up the tank. The higher your initial stores, the further the wall is pushed back — but no amount of loading replaces adequate intake during the race.

After: what the wall teaches you

If you hit the wall, the post-race analysis is valuable: at what kilometre, how many carbs had you actually taken, and had you tested it in training? Most 'walls' come from intake that was too low or too late, not from a lack of talent. Note everything to tune the next plan.

What brings the wall on

Starting too fast and burning through stores early
Starting to fuel too late, once you're already flat
Underestimating carb needs over 3-4 h of effort
Never having tested your target hourly intake in training
Relying on loading alone without fuelling during the race

Practical checklist

Carb loading in the 2-3 days before
Final carb meal 3-4 h before the start
Intake from the first hour, steady every 20-30 min
30-60 g/h, up to 60-90 g/h if trained (glucose + fructose)
Strategy validated on long runs beforehand

FAQ

Running9 min

Marathon nutrition: before, during, after

The marathon needs a progressive strategy: gut training, regular fueling and structured recovery.

Read the guide

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How many gels for a marathon?

The right amount mostly depends on your finish time, your carbs-per-hour target and your digestive tolerance.