How to Fuel an Ultra

When you run or walk for many hours in an ultramarathon, your body needs a steady supply of energy, fluids, and electrolytes to keep moving efficiently and feeling strong.

Carbohydrate is your primary fuel source during endurance exercise, but some runners also benefit from small amounts of protein or fat during longer events to improve satiety, reduce flavour fatigue, and make eating more enjoyable over many hours.

If you don't get the balance right, you risk “bonking” (running out of energy), developing gut issues, cramping, or being forced to slow down significantly.

What Is CHO?

Throughout this guide, you'll see the term CHO, which simply stands for carbohydrate. CHO is the body's primary source of fast energy during endurance exercise and is typically measured in grams per hour (g/hr).

Managing your carbohydrate intake effectively helps maintain energy levels, protect performance, and reduce the likelihood of stomach problems later in the race.

The Science Behind Ultra Fuelling

This guide draws upon the work of leading sports nutrition researchers and practitioners:

Key Takeaways from the Experts

Train Your Gut

Practise your race-day fuelling strategy during training. Your digestive system adapts to regular carbohydrate intake, improving absorption and reducing the likelihood of gastrointestinal issues on race day. (Mysportscience.com)

Use Multiple Carbohydrate Sources

Combining glucose and fructose can increase carbohydrate absorption rates and improve tolerance compared with relying on a single source.

Fuel Consistently

For events lasting more than about 2.5 hours, ACSM and Jeukendrup's guidance goes up to 90 g of CHO per hour, using glucose–fructose mixes. The ISSN's ultra-marathon position stand sets a more conservative baseline of 30–50 g per hour (150–400 kcal per hour), which many slower runners find easier to sustain. In practice, most runners we coach land somewhere between 40 and 90 g per hour — individual needs vary with body size, intensity, experience and gut tolerance.

Include Variety

Some runners enjoy small amounts of protein or fat during longer events, particularly at lower intensities. Real foods, savoury snacks, and comfort foods can reduce flavour fatigue and help maintain appetite over many hours.

Hydrate Smartly

A sensible starting point for most runners:

• 400–800 ml of fluid per hour
• 300–600 mg of sodium per hour

These sit within the ranges in the ACSM and ISSN guidance (the ISSN suggests 450–750 ml per hour, with drinks containing more than 575 mg of sodium per litre). Heavy sweaters, hotter conditions, or very long race durations may require more — but avoid forcing down much more fluid than you lose, as over-drinking dilutes blood sodium.

Practise Everything

Nothing new on race day. Test every product, flavour, timing strategy, and combination during training first. Your body is unique, and what works brilliantly for one runner may not work at all for another.

The Lap: An Example Ultra

The Lap is a 47-mile (75 km) trail ultra that circles England's largest lake, Windermere, in the heart of the Lake District. One of its great advantages is that it is a complete loop, making logistics much simpler than many point-to-point ultras.

The event includes:

• Five feed stations, plus a halfway aid station at Troutbeck
• Water, cordial, real Coke, electrolytes and energy drinks
• A mixture of sweet and savoury food, energy bars, salty snacks and salt
• Hot pizza at the Troutbeck halfway station
• A small shoe-bag drop at Troutbeck — shoes plus whatever fits inside them (the organisers are ending the bag drop after the May 2027 race)
• A finisher's meal at the end

How Much Should You Eat?

The right answer depends on your pace, body size, experience, and goals.

These are our coaching starting points rather than fixed rules — adjust them in training. Most Lap participants fall into the strong recreational category. Steady, consistent fuelling usually wins.

Before the Start

Race-day fuelling begins long before the starting gun. Aim to:

• Eat a familiar carbohydrate-rich breakfast 2–3 hours beforehand.
• Continue sipping fluids before the race.
• Avoid experimenting with new foods.
• Start well hydrated rather than trying to catch up later.

Simple options include porridge with honey and banana, toast with jam, rice pudding, bagels, or overnight oats. Stick with foods you know and trust.

Example Hour-by-Hour Plan (Steady Runner)

Race Start

Begin sipping your electrolyte drink immediately. Target around 20–25 g of carbohydrate within the first 30 minutes.

Every 30–45 Minutes

Consume a gel, energy chews, half an energy bar, banana pieces, or small real-food snacks. Aim for approximately 20–30 g CHO at each feeding opportunity.

At Every Aid Station

• Refill bottles.
• Eat something.
• Top up sodium.
• Grab extra food for the next section.
• Thank the volunteers.
• Keep moving.

Troutbeck (Halfway)

This is your opportunity to reset. Consider pizza, a savoury snack, fresh socks if conditions are wet, refilling all bottles, and reviewing your nutrition plan. Eat properly here rather than relying solely on gels.

Final 10 Miles

Fatigue often reduces appetite. Switch to smaller, more frequent carbohydrate doses, Coke, easy-to-digest foods, and comfort snacks. Keep fuelling even if you don't feel hungry.

Real Food Ideas

Nigel Mitchell and other practitioners highlight the benefits of including real food during longer events. Mixing sweet and savoury foods helps prevent flavour fatigue and keeps eating enjoyable.

• Salted boiled potatoes
• Rice cakes
• Small cheese sandwiches
• Pizza
• Bananas
• Malt loaf
• Ginger biscuits
• Salted crisps
• Peanut butter wraps
• Rice pudding

Using Caffeine Wisely

Caffeine can improve alertness, reduce perceived effort, and provide a useful psychological boost. However, timing matters. Instead of taking large amounts early in the race, many runners benefit from saving stronger caffeine sources for the second half, when fatigue begins to build.

Weather Changes Everything

The Lake District can deliver sunshine, wind, rain, and cold temperatures — all in the same day. Hot weather increases fluid and sodium requirements. Cooler conditions may reduce thirst, but your hydration needs don't disappear. Drink according to your plan and adjust based on conditions.

Female Athlete Considerations

Female athletes may experience different fuelling needs throughout the menstrual cycle. Some runners report increased carbohydrate requirements or altered gastrointestinal tolerance during certain phases. The key message remains the same: experiment during training and build a strategy that works for your body.

Common First-Time Fuelling Mistakes

• Waiting until you're hungry to eat.
• Trying new products on race day.
• Drinking only plain water.
• Carrying only sweet foods.
• Ignoring sodium intake.
• Eating large meals instead of smaller, regular feedings.
• Saving gels “for emergencies.”
• Forgetting to practise nutrition during training.

Race-Day Tips

Eat Early

Don't wait for hunger. Start fuelling within the first 30 minutes.

Mix Sweet and Savoury Foods

Flavour fatigue is real. Variety keeps you eating.

Keep a Backup Supply

Carry emergency carbohydrates and electrolytes even if aid stations are well stocked.

Plan Your Troutbeck Stop

Make Troutbeck as efficient as possible. The bag drop is a small shoe-bag only — shoes plus whatever fits inside them, such as fresh socks and a few favourite snacks — so decide in advance exactly what goes in it. From September 2027 there is no bag drop, so plan to carry everything you need.

Watch Your Gut

If bloating or nausea develops, slow down slightly, reduce carbohydrate intake briefly, sip water, and resume eating gradually. Panic rarely helps. Patience usually does.

Personal Fuelling Checklist

• Practise race-day nutrition during long runs.
• Test all brands and flavours.
• Plan your Troutbeck stop (and shoe-bag, if the bag drop is running for your edition).
• Carry backup carbohydrates and electrolytes.
• Plan your aid station routine.
• Practise your caffeine strategy.
• Train your gut.
• Never try anything new on race day.

Summary

Fuelling an ultramarathon isn't about guesswork. It's about preparation, consistency, and understanding your own body. The science is clear:

• Train your gut.
• Fuel early.
• Stay hydrated.
• Eat consistently.
• Include variety.
• Practise everything.

For most runners, somewhere between 40 and 90 g of carbohydrate per hour is enough — with 90 g the practical ceiling for most, and considerably less often optimal for slower runners. More is not always better. The best fuelling strategy is the one you can execute comfortably from start to finish.

Whether you're racing for a personal best, running with friends, or hiking your way around Windermere, good nutrition can make the difference between surviving an ultra and truly enjoying it.