Race Day Nutrition Plan for Triathlons, Marathons, and Half Marathons

You can’t out-train bad fueling.

Most endurance athletes spend months preparing for race day — but completely guess their nutrition strategy.

If you’ve ever:

• Bonked at mile 18

• Felt nauseous during the bike

• Cramped in the final 10K

• Or faded hard in the last third of your race

It wasn’t fitness.

It was fueling.

Here’s how to build a proper race day nutrition plan for triathlons, marathons, and half marathons.

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Step 1: Pre-Race Breakfast (2–3 Hours Before Start)

Your goal: top off glycogen without upsetting your stomach.

Ideal Pre-Race Meal:

• 60–100g carbohydrates

• 15–25g protein

• Low fat

• Low fiber

Examples:

• Oatmeal + banana + honey

• Bagel with peanut butter

• White rice + scrambled eggs

• Toast + jam + Greek yogurt

Hydration:

• 16–20 oz water upon waking

• Electrolytes if it’s hot or humid

Avoid:

• New foods

• High-fat breakfast sandwiches

• Massive coffee overload

• Fiber bombs

Race morning is not the time to experiment.

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Step 2: Carb Intake During the Race

This is where most athletes mess up.

The science-backed range:

30–90 grams of carbohydrates per hour

The exact number depends on:

• Race length

• Intensity

• Gut training

• Body size

General Guidelines

Half Marathon (1.5–2 hrs)
→ 30–60g carbs per hour

Marathon (3–5 hrs)
→ 60–75g carbs per hour

Olympic Triathlon
→ 45–75g carbs per hour

Half Ironman (70.3)
→ 60–90g carbs per hour

Ironman athletes may tolerate higher amounts if trained properly.

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What to Eat During a Triathlon

Triathlon fueling differs because of transitions.

Swim:

No fueling. Pre-race carbs matter most.

Bike:

This is your primary fueling window.

• Liquid carbs

• Carb mix bottles

• Gels every 20–30 minutes

• Sodium 400–800mg per hour (climate dependent)

Run:

Harder to digest. Simpler carbs work best.

• Gels

• Small sips sports drink

• Avoid solid food unless well trained

Most GI issues start from overloading during the bike.

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Marathon and Half Marathon Fueling Strategy

Running is mechanically harder on the gut than cycling.

Stick with:

• Gels every 25–35 minutes

• Water at aid stations

• Sodium supplementation if sweating heavily

If your pace fades after mile 18, it’s often under-fueling early.

Fuel early. Not late.

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Electrolyte Strategy for Endurance Racing

Cramping isn’t always sodium-related — but heavy sweaters need a plan.

Start with:

• 400–600mg sodium per hour

• Increase toward 800–1000mg in hot races

We’ve seen athletes lose over 1,000mg sodium per liter of sweat in testing.

If you finish covered in salt streaks, you likely need more electrolytes.

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The Biggest Race Day Fueling Mistakes

1. Trying a brand new gel

2. Skipping early carbs

3. Overdrinking water (hyponatremia risk)

4. Ignoring sodium

5. Not practicing race fueling in training

Your gut needs training just like your legs.

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Example 70.3 Race Day Fueling Plan

Pre-race:

• Oatmeal + banana (80g carbs)

• 20oz electrolytes

Bike (3 hours):

• 2 carb bottles (60g each)

• 2 gels

• 1 electrolyte capsule per hour

Run (1:45):

• 1 gel every 30 minutes

• Water at aid stations

Total: ~75g carbs/hour average

That’s controlled, predictable energy.

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How to Train Your Gut

Start practicing during long workouts:

• Begin with 40g carbs/hour

• Increase gradually

• Test different carb sources

• Track GI response

The best race day nutrition plan is one rehearsed in training.

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Final Thoughts

Endurance racing is fueled performance.

A proper race day nutrition plan for triathlon and marathon athletes should:

• Start before the gun

• Fuel consistently

• Match race duration

• Include electrolytes

• Be practiced repeatedly

Fitness gets you to the start line.

Fueling gets you to the finish line strong.

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If you want structured training that integrates fueling strategy into your workouts — not just mileage — TriSchedule builds race prep that includes nutrition timing, carb targets, and recovery planning.

Because race day shouldn’t be guesswork.