How to Fuel a Trail Run: What to Eat and Drink by Distance

01Why you hit the wall

Your muscles burn a mix of fat and carbohydrates. Fat is almost unlimited, but carbohydrates, stored as glycogen in your muscles and liver, run low after roughly 90 minutes to 2 hours of steady running. When they do, everything gets harder: heavy legs, slower pace, bad mood. That is the wall, and on trails it usually arrives around 15 km or 2 hours.

Eating during the run tops up those stores before they run out. It is not about willpower: it is the difference between finishing strong and walking the last hour.

02How much, by how long you run

Time out	Carbohydrates	Fluid	Salt
Under 1 hour	None needed	Only if it is hot	None
1–2 hours	30–60 g per hour	To thirst, about 400–600 ml per hour	Only in heat
2–4 hours	60 g per hour, more if trained	To thirst, about 400–800 ml per hour	Electrolyte drink or salt capsules, especially in heat
Over 4 hours	60–90 g per hour, if your stomach is trained	To thirst, more in heat	Regularly, from the start

General guidelines for healthy adults. Heat, altitude and your own sweat change what you need: adjust in training.

03What 30–60 grams looks like

Food	Carbohydrates
Maurten Gel 100 (40 g)	25 g
Naak Boost gel	30 g
226ERS High Energy gel (76 g)	50 g
Maurten Drink Mix 320, in 500 ml	78 g
A medium banana	About 25 g
Two Medjool dates	About 35 g
500 ml of a typical sports drink	About 30 g

Product values from the brands, as listed in our catalog. Whole foods are approximate.

Gels and drinks to compare

Maurten Gel 100Nutrition$3.41

Näak Boost Gel 30Nutrition$3.85

226ERS High Energy Gel 76gNutrition$3.5

Maurten Drink Mix 320Nutrition$3.43

Gels and drinks

Fast to digest and easy to dose: you know exactly what you take.
Best when the effort is high or the run is long.

Real food

Bananas, dates, boiled potatoes, rice bars: cheaper and kinder on some stomachs.
Works best at easier efforts and on long, slow days.

04Before the run

1
The day before a long run
Normal meals with a bit more carbohydrate (rice, pasta, bread, potatoes). No need for a giant pasta dinner.
2
2–3 hours before
A carb-based breakfast that is low in fibre and fat: oats, toast with honey, rice. Fat and fibre slow digestion and upset stomachs.
3
30–60 minutes before
A small snack if you are hungry: a banana or a few biscuits, and a glass of water.

05During the run

1
Start early
Take your first carbohydrates at 30–45 minutes, before you feel you need them.
2
Little and often
Something every 20–30 minutes digests better than a lot at once. A timer on your watch helps.
3
Take gels with water
A few sips of water with each gel helps it go down and be absorbed.
4
Use caffeine late, if at all
A caffeinated gel can help in the second half of a long run. Test it in training: some stomachs don't like it, and it can stop you sleeping after an evening race.

Time	What
0:40	Gel (25 g) with water
1:10	Half a banana and a few sips of electrolyte drink
1:40	Gel (25 g) with water
2:10	Two dates or a rice bar
2:40	Gel, caffeinated if you tolerate it

Example: a 3-hour trail run at around 50 g of carbohydrates per hour.

06Drinking and salt

For most runners, drinking to thirst works well. What you need depends on heat and on how much you sweat, which varies a lot between people.

When to add salt

Runs over 2 hours, hot days, or if you see white salt marks on your clothes.
Use an electrolyte drink, salt capsules or salty food.

Don't overdrink

Drinking much more than you sweat dilutes the salt in your blood, which can be dangerous.
Gaining weight during a long run is a sign you are drinking too much.

07Train your stomach

Stomach problems are one of the main reasons long trail runs and ultras go wrong, and the gut adapts with practice like your legs do.

1
Start at 30 g per hour
On every run over an hour, even when you don't feel you need it.
2
Add about 10 g per hour every 1–2 weeks
Until you reach what you plan for race day.
3
Practise with your race products
The same gels, drinks and timing, at the effort you will race at.
4
Write it down
What you ate, when, and how your stomach felt. Patterns show up fast.

08How to carry it

From about an hour, a running vest is the most comfortable way to carry water, food and a jacket: soft flasks at the front, food in the side pockets where you can reach it without stopping.

Running vests

Salomon Active Skin 8Vest$80

Salomon ADV Skin 12Vest$165

09After the run

Within an hour or two

Carbohydrates to refill your stores, plus about 20–30 g of protein for your muscles.
A normal meal does the job: rice with eggs, a sandwich, yogurt with fruit and oats.

Rehydrate

Drink until your urine is pale again.
After long or hot runs, add some salt: a salty meal or an electrolyte drink.

Frequently asked questions

How many gels do I need for a trail half marathon?

It depends on how long you will be out. For a 2.5–3 hour race at 40–60 g of carbohydrates per hour, that is about 4–6 gels of 25 g, or fewer if you also drink an energy drink.

Are gels better than real food?

Neither is better for everyone. Gels are quick and easy to dose; real food is cheaper and some stomachs prefer it on long, slow runs. Many runners mix both.

Do I need to eat on a 1-hour run?

No. Your glycogen stores cover an hour of running. Water is only needed if it is hot.

Does salt prevent cramps?

Not reliably. Cramps are mostly linked to fatigue and to running harder or longer than you trained for. Salt matters for long or hot runs, but training is the best prevention.

Why does my stomach hurt when I eat while running?

Usually too much at once, too much fat or fibre before the run, a product you are not used to, or a gut that is not trained yet. Start with smaller amounts more often and build up.

Next steps

Compare gels and drinksCarbs, caffeine and price per serving Strength for trail runnersGet past the other wall: your legs Compare running vestsCapacity, pockets and fit