The Complete Marathon Nutrition Guide

Everything you need to know about fueling a marathon — from pre-race carb loading to mid-race gel strategy and post-race recovery.

The marathon is 26.2 miles. At race pace, you'll burn through your glycogen stores in roughly 90-120 minutes. The race is twice as long. That gap is where nutrition becomes the difference between a strong finish and hitting the wall.

This guide covers everything you need to fuel a marathon well — from the week before to the finish line.

The week before — carb loading

Carb loading isn't about eating pasta the night before. That's a myth that leads to heavy legs and a poor night's sleep.

Effective carb loading means gradually increasing carbohydrate intake over 2-3 days before the race while reducing training volume. The goal is to top up muscle glycogen stores beyond their normal resting level.

Target 8-10g of carbohydrate per kg of body weight per day for the 2-3 days before the race. For a 70kg runner, that's 560-700g of carbs daily — significantly more than a typical diet.

Focus on easily digestible sources: white rice, pasta, bread, potatoes, bananas, sports drinks. Reduce fiber, fat and protein relative to normal. This reduces gut bulk and minimizes the risk of GI issues on race day.

Race morning — the pre-race meal

Eat 2-3 hours before the start. The goal is to top up liver glycogen (which depletes overnight) without leaving food sitting in your stomach at the gun.

A good pre-race meal for a 70kg runner:

Total: approximately 150g carbs, low fiber, low fat.

60 minutes before the start, sip 500ml of water or dilute sports drink. Avoid high-fibre foods from this point.

15-20 minutes before the gun, take a caffeine gel if using caffeine strategy — this times the peak caffeine effect with the early race miles.

During the race — gel strategy

For marathon running, target 60g of carbs per hour. Elite runners may push to 90g/hr but this requires gut training and a carefully planned dual-transporter approach.

A simple gel strategy for a 4-hour marathon:

For a 4-hour race you'll need approximately 8-10 gels depending on carb content. Pack more than you think you need.

Sodium matters. At marathon pace you'll lose 1-2g of sodium per hour through sweat. If you're only taking gels, supplement with electrolyte capsules or choose gels with higher sodium content. Cramping in the late miles is often sodium depletion, not just fatigue.

The wall — and how to avoid it

Hitting the wall is glycogen depletion. It happens when you've burned through your stored carbohydrates and your body switches to fat oxidation — a much slower fuel source.

The wall is avoidable with two things:

First, start fueling early and consistently. Most runners start too late and try to catch up. You can't. Once glycogen is depleted, no amount of gels will bring it back in the time available.

Second, pace correctly. Going out too fast in miles 1-10 burns glycogen at an accelerated rate. Even 10-15 seconds per mile too fast in the early miles can determine whether you have energy for the final 6.

Post-race recovery

The 30-minute window after finishing is the most important nutrition moment of the day. Muscle cells are maximally receptive to glucose uptake and protein synthesis.

Don't skip the post-race meal because you feel nauseous. Start small with liquid nutrition if needed — a protein shake, a banana, sports drink — and build from there.

Caffeine strategy

Caffeine is one of the most evidence-backed ergogenic aids in sport. For marathon running, a well-timed caffeine strategy can meaningfully improve late-race performance.

Options:

If you're not a regular caffeine user, start with a lower dose and test in training first. GI sensitivity to caffeine varies significantly between individuals.

Practice everything in training

The single most important piece of advice in this guide: practice your race nutrition in training. Long runs are dress rehearsals for your gut as much as your legs.

Take gels at race pace. Drink from cups while running. Test your pre-race meal. Try your caffeine strategy. Everything that goes into your body on race day should have been tested at least twice in training.

Race day is not the time to try a new gel.