Guide By EnduriFit Team October 11, 2026 · 5 views

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Fuelling a 50km trail run is meaningfully different from road marathon nutrition. It is only 8km further than a marathon on paper, but once you add climbing, technical terrain, heat and hiking sections, most runners will be out there for somewhere between five and nine hours. That is long enough for pre-race glycogen stores to be a small part of the story, and long enough for small fuelling mistakes in the first two hours to turn into a full-blown blowup at kilometre 35.

This guide covers how many calories and grams of carbohydrate you need per hour, the role of real food versus gels, sodium replacement in Australian heat, how to use aid stations efficiently, and the timing mistakes that cause late-race collapses. Whether you are training for Ultra-Trail Australia's 50km, a Victorian or Tasmanian mountain race, or your first local trail 50, the principles are the same.

Why 50km Trail Fuelling Is Different

• Duration: most runners take 5–9 hours, compared with 3–5 hours for a road marathon
• Variable intensity: steep climbs push heart rate high; descents and hiking sections lower it. Fuelling opportunities change with the terrain
• Self-sufficiency: aid stations can be 8–15km apart, so you must carry fuel and fluid between them
• Gut stress: jarring descents and heat make digestion harder than on smooth roads
• Flavour fatigue: after four hours of sweet gels, many runners simply cannot face another one
• Lower average intensity: you use a slightly higher proportion of fat as fuel, which makes real food more viable than in a road race

How Much Should You Eat Per Hour?

Carbohydrate

For events longer than 2.5–3 hours, sports nutrition guidelines recommend 60–90 g of carbohydrate per hour. Most recreational trail runners will do well at 60–75 g per hour; well-trained runners who have practised gut training can push towards 90 g per hour using glucose–fructose products.

If you currently eat 30 g per hour on long runs, do not jump to 90 g on race day. Increase gradually in training — your gut adapts to carbohydrate intake in much the same way your legs adapt to mileage.

Calories

A practical target for most runners is 200–300 calories per hour, the majority from carbohydrate. You will burn far more than this — often 600–900 calories per hour — but you cannot absorb that much, and you do not need to replace it all. The aim is to supply enough carbohydrate to keep glycogen from running out.

Fluid

Fluid needs depend heavily on temperature, sweat rate and humidity. Typical intakes range from 400–800 ml per hour. Drink to thirst, guided by sweat rate testing in training, and avoid drinking so much that you gain weight.

Sodium

For a 50km event, aim for roughly 300–600 mg per hour in mild conditions, and 600–1,000 mg per hour if you are a heavy or salty sweater racing in heat. Our electrolytes and sodium guide explains how to estimate your personal needs.

Gels, Drinks or Real Food?

The best trail fuelling strategies use a combination.

Gels and Chews

Gels are compact, predictable and fast-digesting — ideal for the first half of the race and for higher-intensity sections. Products with 40 g of carbohydrate or more per serve, such as SiS Beta Fuel or Maurten Gel 160, reduce the number of packets you need to carry. Chews such as Clif Shot Bloks are easy to portion on hiking sections.

Drink Mixes

Carbohydrate-electrolyte drinks deliver energy, sodium and fluid together and are easy on the stomach. Tailwind is commonly stocked at Australian trail events. Many runners carry one flask of drink mix and one of water, giving them flexibility when it is hot.

Real Food

Real food adds variety, satisfies hunger and often provides salt. It digests more slowly, which suits the lower-intensity second half of a 50km. Proven options include:

• Boiled baby potatoes rolled in salt
• White bread sandwiches with honey, jam or Vegemite
• Rice balls or sushi rolls
• Bananas and watermelon at aid stations
• Pretzels, salted crackers and potato chips
• Jelly lollies
• Flat cola (usually from the halfway point onwards)

Avoid high-fat, high-fibre or high-protein foods mid-race; they sit heavily in the stomach. Our natural vs synthetic gels comparison explores the trade-offs in more depth.

Sample Fuelling Plan: 6:30 Finish

This example is for a 70 kg runner targeting around 70 g of carbohydrate per hour in mild conditions. Adjust quantities to your own targets.

Time	Fuel	Approx. carbs
3 hours before	Breakfast: white bagel with honey, banana, sports drink	120–150 g
15 min before	1 gel with a few sips of water	25 g
Hours 1–2	500 ml drink mix per hour + 1 gel every 45 min	~75 g/hr
Hours 3–4	Drink mix + 1 gel per hour + chews or salted potatoes at aid station	~70 g/hr
Hours 5–6.5	Drink mix + caffeinated gel + flat cola and watermelon at aid stations	~65 g/hr

Notice that the plan starts fuelling within the first 30–45 minutes. Waiting until you feel hungry is too late.

Timing Mistakes That Cause Late-Race Blowups

1. Starting Too Late

The most common error. Runners feel great in the first hour, skip fuelling, and then find themselves in a deep energy hole at 30km. Glycogen debt accumulated early is very hard to repay later because your gut can only absorb so much per hour. Start eating within the first 30–45 minutes and keep going regularly.

2. Eating Only at Aid Stations

Aid stations may be 90 minutes or more apart on a mountainous course. Eating a big load at each station and nothing between creates energy peaks and troughs, and overloads your stomach. Little and often — every 20–30 minutes — is far better.

3. Front-Loading Too Hard

The opposite problem: smashing three gels in the first hour while running hard up the first climb. Your stomach struggles to process concentrated sugar at high intensity. Keep effort controlled early and spread intake evenly.

4. Ignoring Fuelling on Climbs

Long, steep climbs often slow you to a hike — and hiking is the best time to eat. Your heart rate is moderate, your stomach is stable, and your hands are free. Use the climbs to get food in; descents are much harder to eat on.

5. Under-Drinking in the Heat, or Over-Drinking in the Cold

Australian trail races can swing from cold, wet starts in the mountains to hot afternoon finishes. Adjust fluid to conditions rather than following a fixed schedule.

6. Trying New Products on Race Day

Know what will be at the aid stations, and test those exact products in training. If the race uses a drink brand you have never tried, either practise with it or carry your own.

Dealing with Gut Problems on the Trail

Nausea and stomach upset are among the most common reasons for poor performances and DNFs in trail running. If your stomach turns:

1. Slow down — reducing intensity diverts blood back to the gut
2. Cool down — overheating is a major cause of nausea; use water on your head and neck
3. Switch to small sips of plain water or flat cola
4. Try something salty and bland — crackers, potato or broth
5. Resume fuelling gradually as soon as the nausea settles; continuing to starve will create an energy crash

Ginger chews or crystallised ginger help some runners. Prevention, through gut training, is far more effective than cure.

Gut Training: Teaching Your Stomach to Eat on the Run

Your gut can be trained to absorb more carbohydrate and tolerate food during exercise. Over 6–10 weeks before your race:

• Practise race-day fuelling on every long run of 2 hours or more
• Gradually increase carbohydrate per hour (for example 40 g → 55 g → 70 g)
• Rehearse with the same products, flavours and timings you will use on race day
• Include some runs in the heat and on hilly terrain so your gut adapts to race conditions
• Eat a full breakfast before some long runs to replicate race morning

Carrying Your Fuel

A well-fitted hydration vest is essential for most 50km trail races, and many events have mandatory gear lists that require one anyway. Look for:

• Front pockets that fit soft flasks and gels within easy reach
• At least 5–8 litres of capacity for mandatory gear
• Minimal bounce when full
• Zip pockets for rubbish — always carry out your wrappers

Compare options in our guides to the best running hydration vests and best budget trail hydration packs, or read our Ultimate Direction vs Salomon vest comparison.

Race Week Nutrition

A full marathon-style carb load is useful before a 50km but slightly less critical because in-race fuelling makes up a larger share of your energy needs. A sensible approach:

• Increase carbohydrate to 8–10 g per kg of body weight per day for 36–48 hours before the race. Our carbohydrate loading guide explains how
• Reduce fibre and fat in the final 24–48 hours
• Stay hydrated, and consider sodium pre-loading if the race will be hot
• Eat a familiar, carbohydrate-rich breakfast 2–4 hours before the start

Using Aid Stations Efficiently

Time spent standing at aid stations adds up quickly over a 50km — five stops of four minutes each is 20 minutes. Efficient runners treat every aid station like a pit stop:

• Plan before you arrive: in the final kilometre, decide what you need — refill flasks, grab food, apply sunscreen — so you are not standing around deciding
• Open your flasks early: unscrew lids as you approach so volunteers can fill them immediately
• Take food to go: grab a handful of potatoes or a sandwich quarter and eat while walking out
• Use drop bags strategically: if the race allows them, pack your preferred fuel, a spare pair of socks and any medications
• Check the race's aid station menu on the event website in advance and train with those products

Most Australian trail races also run cupless aid stations for environmental reasons, so you will need your own collapsible cup or soft flask to drink from.

Caffeine Strategy

Caffeine can provide a valuable lift in the second half of a long trail race. Rather than a large dose at the start, many runners take small amounts (25–50 mg) from the halfway point onwards, or save a caffeinated gel for the final big climb. Our running and caffeine guide covers dose and timing.

Recovery After Your 50km

Once you finish, start eating within an hour: aim for a combination of carbohydrate and around 20–40 g of protein, plus fluids and some salt. Flavoured milk, a sandwich, or a recovery shake are all good options. Continue eating regular carbohydrate-rich meals for the next 24–48 hours to restore glycogen. Our recovery guide covers the rest.

Frequently Asked Questions

Can I run a 50km trail race on just water and gels?

Some runners do, but most benefit from adding sodium and some real food. Gels alone often lead to flavour fatigue and inadequate sodium intake over 6+ hours.

How many gels do I need for a 50km?

If gels are your main fuel and each contains around 25 g of carbohydrate, you would need 2–3 per hour — potentially 15 or more for a seven-hour race. That is why most runners combine gels with drink mixes and real food.

Is fat-adaptation useful for trail ultras?

Some ultra runners experiment with low-carbohydrate training, but the evidence suggests carbohydrate fuelling still supports better performance, particularly on climbs and in the final hours. For most runners, a carbohydrate-based race strategy is the better choice.

The Bottom Line

Successful 50km trail fuelling comes down to starting early, eating little and often, targeting 60–90 g of carbohydrate per hour with adequate sodium, and combining gels, drink mixes and real food to suit the terrain and conditions. Use climbs to eat, adjust fluid to temperature, and rehearse everything in training. Get it right and the final 15km becomes a strong, steady finish rather than a survival shuffle.

This article is general information only. For a personalised race nutrition plan, consult an Accredited Sports Dietitian.

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