Running guide

Marathon fueling: carb loading, race morning, and in-race strategy

Marathon fueling starts well before the gun goes off. By the time you're on the start line, the carb loading and the training-run rehearsals should already be done — race day is just executing the plan.

Carb loading in the days before

Deliberately increasing carbohydrate intake for a day or two before the race is a widely used way to maximize glycogen stores for an effort this long. It's worth doing for a marathon you're actually racing, and matters less if you're running one at an easy, non-racing effort.

Race-morning breakfast

Eat something carbohydrate-focused, familiar, and easy to digest, 2–4 hours before the start — whatever has worked in your long-run rehearsals. Race morning is not the time to try a new breakfast, however good it sounds.

In-race fueling strategy

Set your target from carbs per hour running, then work out roughly how many gels or equivalents that means for your expected finish time, and when you'll take them — many runners plan a gel every 25–40 minutes, adjusted to their own target and tolerance. Whatever the plan, it should already be familiar from long-run rehearsals, not improvised on the day.

Why runners crash after halfway

A common pattern: starting a little faster than goal pace, plus under-fueling in the first half because everything still feels fine, catches up once glycogen actually runs low — usually somewhere past halfway. Both sticking to planned pace and fueling from early in the race, not just when you start to feel it, help avoid this.

Aid-station strategy

Know the course's aid-station spacing in advance and decide whether you're relying on it for fluids, carbohydrate, or both. If you're using your own gels for carbohydrate and course drinks for fluid only, plan for that split rather than figuring it out mid-race.

Common mistakes

  • Skipping carb loading because it feels unnecessary. It's specifically useful for an effort this long and this depleting.
  • New shoes, new breakfast, or a new gel on race day. Anything new belongs in a training run first.
  • Fueling reactively instead of on a plan. By the time you feel low, you're already behind for the rest of the race.
  • Ignoring pacing's role in your fueling needs. A too-fast start changes the math on how much fuel you'll actually need.

Related guides

How many carbs per hour should you eat while running?The target this race-day plan is built around. Long-run fuelingWhere this plan should already have been tested. Fueling before exerciseMore on carb loading and race-morning timing. Fueling after exerciseRecovering once you're across the line.

Frequently asked questions

Do I really need to carb load before a marathon?

For most runners aiming to race a marathon, yes — it's a widely used technique to maximize glycogen stores for an effort that will draw heavily on them. It matters less for a marathon run at an easy, non-racing effort.

What should I eat on marathon morning?

A carbohydrate-focused breakfast 2–4 hours before the start, familiar to your stomach from training, is the safest bet. This isn't the morning to try something new.

How many gels do I need during a marathon?

It depends on your target carbs per hour and your finish time, not a fixed number that applies to everyone. Work backward from your hourly target and your expected pace to figure out roughly how many you'll need, then practice that exact count in training.

Why do I feel fine at halfway and then crash?

This is often a combination of starting faster than race pace and under-fueling early, so the deficit only shows up once stored glycogen actually runs low, typically somewhere past halfway.

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