20. April 2026

The Ultimate Beginner’s Guide to Ultra Marathon Nutrition (50K to 100 Miles)

By Ultrarunner.life – Sports Therapy & Running Coaching Experts

Introduction: Welcome to the Buffet of Suffering

If you’ve signed up for your first ultra-marathon, congratulations—you’ve officially decided that running a marathon just isn’t painful enough!

Now comes the real challenge: not the hills, not the distance, not even the questionable life choices… but eating. Constantly. While running. For hours. Sometimes days.

Ultra marathon nutrition is the difference between feeling like a durable mountain goat and a melted candle somewhere around mile 37.

This guide is your one-stop, no-nonsense (okay, some nonsense) beginner’s roadmap to fueling your body for races from 50K all the way to 100 miles.

We’re going deep. Science, real-world experience, mistakes (so many mistakes), and practical strategies you can actually use.

When planning your hydration strategy, remember no plan survives first contact with the enemy! Stick to your plan but adjust accordingly. If you are thirsty, drink more. Same for nutrition, if you are hungry, put a little more fuel in. If at any point you are concerned and your health may be at risk, seek assistance from other competitirs, medical staff, or call the race director on the emergency number. Always have an ICE contact on your race number and in your phone!

There are reasons races like UTMB Arc of Attrition get renamed Arc of Nutrition! They are a great reason to consume a lot of food that we might normally avoid, but doing it in the right way is where it gets interesting.

Why Nutrition Matters More Than Your Fancy Shoes

You can have the best shoes, watch, and training plan—but if your nutrition fails, everything fails.

In ultra running, you are essentially:

Burning 400–800+ calories per hour
Depleting glycogen stores within 60–120 minutes
Losing electrolytes through sweat
Gradually questioning your life decisions

Nutrition and hydration are not optional—it’s performance-critical.

The Golden Rule: Eat Before You’re Hungry, Drink Before You’re Thirsty

Simple? Yes. Easy? Not at mile 62 when your brain thinks a gel is a personal attack.

But this rule is everything.

Set a timer. Follow a schedule. Future-you will be grateful. I like to set two one every 10 minutes to hydrate, one every 30 minutes to eat. In 50k's I like to eat every 20 minutes as the pace is slightly higher.

Understanding the Basics: What Your Body Needs

Carbohydrates: Your Primary Fuel

Carbs are king. Emperor. Supreme ruler.

60–90g/hour standard
Up to 120g/hour with gut training

Multiple transportable carbs (glucose + fructose) increase absorption. SIS and Enervit come in convenient 40g, Stryky do a 50g option as well!

Fats: The Slow-Burning Backup

Useful in longer events but not fast enough alone.

Protein: The Repair Crew

Helpful in events over ~6–8 hours

5–10g/hour can reduce muscle breakdown

Electrolytes: The Silent MVP

Without sodium, everything falls apart. Electrolye tablets and drinks often give 300-400mg of sodium per hour, we tend to lose between 1000-1700mg per hour, especially on warmer days. This where you can either opt for a Precision Hydration 1000/1500mg tablet or get your sweat loss tested properly (we can help with that).

Fuelling by Distance

50K Strategy

200–300 kcal/hour
Mostly carbs
Minimal solids

50 Mile Strategy

250–350 kcal/hour
Introduce real food early

100K Strategy

Mix liquids + solids
Aggressive carb intake

100 Mile Strategy

300–400+ kcal/hour
Include protein + fats
Plan for night eating

Hydration: The Fine Line Between Smart and Sloshy

400–800ml/hour
Adjust for heat

Signs you’re off:

Too little: dizziness, dark urine Too much: bloating, confusion

Electrolytes: Don’t Skip This (Seriously)

Sodium: 300–800mg/hour
Increase in heat/sweat-heavy runners

Gut Training: The Skill Nobody Talks About

Train your stomach like you train your legs.

How:

Practice race fuelling in long runs
Build up carb tolerance
Try worst-case scenarios

Yes, it’s uncomfortable. That’s the point. I once did 20 miles on a treadmill, ate sweets and crisps every 15 minutes, just to see what I could do. Train with the nutrition that you plan to race with, and make sure you do this with the same hydration, at the same intensity, and same environmental conditions that you might face on race day.

Pre-Race Nutrition Strategy

48 Hours Before

Increase carbs
Reduce fibre (avoid “emergencies”)

Race Morning

300–600 calories
Low fibre, familiar foods

Race-Day Nutrition Checklist (Save This!)

✔ Fuel plan written down
✔ Backup foods packed
✔ Electrolytes ready
✔ Bottles/flasks pre-filled
✔ Timer set for eating
✔ Drop bags organised
✔ “Emergency snacks” (the emotional support kind)

Post-Race Recovery Nutrition

Immediately

Carbs + protein

First 24 Hours

Rehydrate
Eat balanced meals

Also: celebrate. Preferably with something greasy.

Caffeine Strategy: Rocket Fuel (If Used Right)

Caffeine is a powerful performance enhancer—but it can backfire.

Benefits

Reduced perceived effort
Increased alertness
Improved endurance

Strategy

1–3 mg/kg doses
Use later in race (not all at once)

Warning

Too much = jittery disaster + stomach issues

Supplements for Ultra Runners

Useful

Electrolyte tablets
Energy gels/chews
Caffeine

Situational

BCAAs (very little evidence that these do much at all but wanted to include them as some people disagree)
Beta-alanine (more for shorter events and make sure you test them, they often come with caffeine if in can form)

Not Magic

If your nutrition plan is bad, no supplement will save you.

Gender-Specific Nutrition Considerations

Female Athletes

Higher risk of low energy availability
Iron levels critical
Hormonal fluctuations affect fuelling needs

Male Athletes

Often under fuel early (ego issue, let’s be honest)

Key Takeaway

Personalisation matters more than gender stereotypes.

Dealing with Common Problems

Nausea

Slow down
Switch to liquids
Try ginger (can be chewable or lozenges)

Cramping (if serious then seek medical attention or call race organisers)

Increase sodium
Adjust pacing

Bonking

Eat immediately
Reduce intensity

Building Your Personal Plan

Calculate calorie needs
Test in training
Adjust for terrain/weather
Build variety
Keep it simple

Advanced Tips from Ultrarunner.life Coaches

Variety prevents flavour fatigue
Real food becomes essential over time
Walk breaks help digestion
Don;t take on nutrition with high HR or on hills)
Small, frequent fuelling beats large doses

The Psychology of Eating During Ultras

At some point, eating becomes emotional.

You’ll hate food. Then love it. Then hate it again.

That’s normal.

Sample Nutrition Plans

Beginner 50K

Gel every 20-30 min
Electrolytes hourly

Intermediate 50 Mile

Mix gels + real food
250–300 kcal/hour

100 Mile Plan

Rotate sweet + savoury
Include warm foods at night

Final Thoughts: Eat Like Your Race Depends on It (Because It Does)

Ultra nutrition is messy, personal, and constantly evolving.

The goal isn’t perfection—it’s consistency.

And maybe not crying over mashed potatoes at mile 80.

I have written a small article on my personal nutrition strategies that you might to borrow something from:

Nutrition Strategies......

Scientific Research Studies

Jeukendrup, A. (2014). A Step Towards Personalized Sports Nutrition.
Burke, L. M. (2015). Re-examining High-Fat Diets for Sports Performance.
Stellingwerff, T. & Cox, G. R. (2014). Carbohydrate Supplementation.
Hoffman, M. D. (2015). Hydration in Ultra-Endurance Events.
Costa, R. J. S. et al. (2017). GI Issues in Endurance Athletes.
Pfeiffer, B. et al. (2012). Carbohydrate Absorption.
Sawka, M. N. et al. (2007). Fluid Replacement.
Cermak, N. M. (2013). Protein & Endurance.