Ultra and trail running nutrition for long days on your feet

At a glance

• Energy demands: Very high, often beyond what you can eat
• Event length: Several hours to multiple days
• Key skill: Eating and drinking while moving
• Common issue: Gut problems and late-race appetite loss

Why ultra running is a fuelling sport

Ultra and trail events range from mountain races of a few hours to multi-day and non-stop events lasting a day or more. Intensity is lower than in road racing, but the total energy cost is enormous, and most runners cannot eat enough on the move to match it. The aim is not to replace everything, but to limit the deficit so that energy, concentration and decision-making hold up into the later stages.

Terrain shapes everything. Long climbs are often hiked, descents batter the legs, and checkpoints may be hours apart, so runners carry much of their own food and fluid. Weather can swing from heat in a valley to cold and wet on a ridge, changing sweat losses, appetite and the risk of getting cold when energy runs low. Night sections add sleep deprivation, which blunts hunger.

Training involves back-to-back long runs, vertical gain and time on feet, usually fitted around work and family, which makes everyday fuelling easy to neglect. Gut problems are among the most common reasons runners slow down or drop out, and they are trainable: real food, flavour variety, sodium and fluid all need rehearsing in conditions as close to race day as possible.

Nutrition priorities for ultra and trail runners

Fuel big training weekends

On days with more than 4–5 h of training, carbohydrate needs can reach 8–12 g/kg/day, while lighter days need far less. We help you scale intake to the week rather than eating the same every day. [1]

Set a realistic hourly target

For events beyond 2.5–3 h, up to 90 g/h of carbohydrate from multiple transportable sources such as glucose–fructose can be beneficial. Many ultra runners start lower and build tolerance over months. [1]

Mix real food and sports products

Sweet gels alone become hard to face after many hours. We build a menu of savoury and sweet options matched to the checkpoints and to what you can carry.

Manage fluid and sodium

Aim to avoid losing more than 2% of body mass through sweat, without drinking well beyond thirst, which carries its own risks on long, slow days. Sweat and sodium losses vary widely, so we personalise them. [1]

Plan caffeine for the night

Caffeine at 3–6 mg/kg about 60 min before exercise is an evidence-based option. In ultras, many runners save some for night sections to support alertness; we check your tolerance and total intake. [2]

Avoid chronic under-fuelling

High volume and a culture of running light make low energy availability common in ultra running, with effects on hormones, bone, immunity and mood. We screen for RED-S warning signs. [3]

Ultra race-day fuelling

1. The days before: Raise carbohydrate towards 10–12 g/kg/day over the final 36–48 h where your plan calls for it, and pack and label your race food by section. [1]
2. Before the start: Have a familiar meal providing 1–4 g/kg of carbohydrate 1–4 h before the start, allowing extra time for early starts and travel to the race. [1]
3. On the course: Eat little and often from the first hour, building towards your rehearsed hourly target, and decide in advance which checkpoints are for real food, fluid and sodium.
4. After the finish: Rehydrate, then eat carbohydrate and protein as your appetite returns. We plan the following days too, because recovery from an ultra takes far longer than the run itself.

General guidance from sports nutrition consensus statements. Your practitioner will tailor amounts to you.

Race formats and their demands

Mountain and trail races

Steep climbs and technical descents mean constant changes of pace, with food and fluid carried between sparse checkpoints.

Road and track ultras

Steady effort and frequent aid make higher hourly intakes achievable, but food monotony and gut fatigue become the limiter.

Overnight and 100-mile events

Sleep deprivation suppresses appetite, so a fixed eating schedule and caffeine planning matter most.

Multi-day stage races

Evening recovery meals and carrying enough self-sufficient food become as important as fuelling each stage.

What we help with

• Nausea or vomiting in the later stages of races
• Appetite loss overnight or after long climbs
• Planning food for long gaps between checkpoints
• Fatigue, illness or injury in high-volume training blocks
• Getting sodium and fluid right in heat or cold
• Under-fuelling while fitting training around work and family

Ongoing support, not one-off sessions

We do not work with athletes on a one-off basis. Sports nutrition works best when it adapts to your training, so we recommend an initial consultation followed by at least three follow-ups.

Who you could work with

• Jenaed Ruddock, HCPC-registered Sports Dietitian (SENr)
• Beatriz Ribeiro, HCPC-registered Dietitian
• Melissa Bosch, Eating Disorder Nutrition Specialist

Book your consultation

Book an initial consultation or book a free discovery call to talk it through first. All consultations are online.

Explore more

See all the sports we work with, our RED-S nutrition support, or meet the team.

Frequently asked questions

How much carbohydrate should I eat per hour in an ultra?

For events lasting longer than 2.5–3 h, guidance supports up to 90 g/h, using products that combine glucose and fructose. In practice, many ultra runners work up to this over months of gut training, and intake often dips overnight or on steep climbs. We set a target that is ambitious but realistic for you.

Is fat adaptation better for ultra running?

Low-carbohydrate, high-fat diets increase the body's use of fat, but they can reduce its ability to use carbohydrate at higher intensities, such as climbs and the final push. For most runners we prioritise carbohydrate availability for key sessions and races. If you are considering a different approach, we talk through the evidence honestly.

What should I eat at checkpoints?

Foods you have tested in training, ideally a mix of sweet and savoury that is easy to chew and carry. We review the race's published checkpoint menu and build your plan around it, with your own food for the long gaps.

How do I stop feeling sick late in a race?

Late-race nausea often follows a spell of under-eating, overly concentrated drinks, heat or pushing too hard on climbs. We look at when your symptoms start in training and races, then adjust products, concentration, timing and fluid. Persistent or unusual symptoms should be checked by your GP.

How many sessions will I need before my race?

We do not work with athletes on a one-off basis, and an ultra plan rarely works perfectly first time. We recommend a minimum of three follow-up consultations after your initial consultation, so we can refine your fuelling across long runs, back-to-back weekends and a race rehearsal.

References

1. Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3):501–528.
2. Maughan RJ, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.
3. Mountjoy M, et al. 2023 International Olympic Committee (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073–1097.