Ultramarathon Nutrition: How to Eat for 50+ Miles

50 miles. 100 miles. These distances break athletes in ways training never can.

The problem isn't your legs. It's not your fitness. It's the simple math: you're about to burn 5,000–10,000 calories, and your body can only store about 2,000.

Fueling an ultramarathon is a skill. Here's how to master it.

Let's be direct about what's coming:

Your body can store 400–600 g of glycogen. Everything else must come from what you eat and drink during the race.

Research shows endurance athletes can absorb 200–350 calories per hour from a mix of sources. Here's the breakdown:

• Carbs: 60–90 g per hour (240–360 calories)
• Total calories: 200–300 per hour from all sources
• Fluids: 400–800 ml per hour (adjust for heat)
• Sodium: 500–1,000 mg per hour (heavy sweaters need more)

Yes, you're reading that right. You need to eat continuously, every hour, for 10+ hours.

Mixing sources prevents palate fatigue and GI issues:

• Gels and chews: Fast-acting, easy to carry, familiar (25–30 g carbs each)
• Drink mixes: Steady carbs, hydration, and electrolytes in one (30–50 g carbs per bottle)
• Solids: Real food for variety and fullness (50–100 g carbs per serving)
• Savory options: Soup, potatoes, pretzels for salt and variety

Here's a sample plan:

Total for a 10-hour 50-miler: 600–700 grams of carbs (2,400–2,800 calories) from food and drink.

Ultras are won and lost at aid stations. Here's how to own them:

• Walk through aid stations. Running wastes energy and increases GI stress.
• Plan your stops. Know what's available and what you need.
• Eat what you've practiced. Aid station food should be familiar.
• Fill bottles and pack pockets before leaving.
• Spend 2–3 minutes eating, then get moving.

Common aid station foods: potatoes with salt, fruit, soup, chips, pretzels, candy, soda (yes, soda works).

You can't show up to a 50-mile race and suddenly eat 300 calories/hour. Your gut needs 8–12 weeks of training:

• Week 1–2: Practice eating 150–200 calories/hour on long runs
• Week 3–4: Build to 200–250 calories/hour
• Week 5–6: Test race-day foods and timing
• Week 7–8: Reach 250–300 calories/hour with diverse sources
• Week 9+: Simulate race conditions with back-to-back long runs

Key rule: If you haven't eaten it on a 20-mile training run, don't eat it on race day.

Many runners drop at 50 miles not because of their legs, but because they stopped eating. Here's what happens:

• You feel nauseous, so you skip a gel.
• An hour later, you're dizzy and can't keep anything down.
• You slow to a walk, then a shuffle, then you're done.

The solution: eat before you're hungry, drink before you're thirsty, and accept that discomfort is part of the deal.

• Carry gels and chews for the first 10–15 miles.
• Rely on aid stations for fluids and solids after that.
• Know the aid station locations and cutoffs.
• Have a backup plan if an aid station is closed or out of supplies.

• Skipping calories because of nausea (makes it worse)
• Drinking only water (causes hyponatremia and GI distress)
• Trying new foods on race day
• Not practicing aid station foods
• Walking aid stations without eating
• Fueling inconsistently (feast or famine)