Aiming For An Ultra-Marathon: How To Up Your Nutrition Game

Ultra-running asks something different of the body than a marathon does. Where a marathon is a hard, glycogen-fuelled push lasting a few hours, an ultra is a multi-hour (sometimes multi-day) negotiation between energy in and energy out, run on tired legs, a reluctant gut, and - just as much - a tiring mind. The athletes who finish strong tend to treat fuelling less like a single race-day decision and more like a skill they've trained - as adaptable and well-rehearsed as their legs.

Table Of Contents

• Why Ultra-Marathon Fuelling Is Different

• Train Your Gut: Eat Early, Eat Often

• Carbohydrate Strategy: How Much, And What Kind

• Protein & Fat: The Macronutrients Everyone Forgets

• Electrolytes & Avoiding Hyponatremia

• Mental Energy Matters: Fuelling The Brain, Not Just The Legs

• Caffeine: Using It Strategically

• Putting It Together: A Sample Race-Day Fuelling Plan

• Take-Home Points

Why Ultra-Marathon Fuelling Is Different

Marathon fuelling advice – a gel every 20 minutes, water at every aid station – breaks down once you're out on course for six, twelve, or twenty-four hours. Three things change: total calories needed go up, and gels alone can't cover it without wrecking your stomach¹˒²; lower intensity means the body leans more on fat, so metabolic flexibility matters²; and the gut itself becomes the limiter, with GI discomfort a leading reason athletes slow down or drop out¹˒³.

An ultra rewards a body that can adapt on the move. Your nutrition plan needs to flex too – different foods, different intake rates, and more tolerance for savoury, dense, "real" food as the race wears on¹.

Train Your Gut: Eat Early, Eat Often

The gut is trainable. Repeated exposure to carbohydrate and mixed foods on long runs improves absorption and reduces bloating, cramping, and nausea – this is "gut training", and it should start months out, not the week before¹˒³. Train on the same foods, in the same order, you plan to eat on race day, building volume gradually rather than trying something new mid-race³. Whole foods belong in the mix alongside gels, especially as races extend past marathon distance and appetite for sweet, gel-like products drops off¹.

A few reliable options to train with:

• Pikelets with nut butter

• Hot cross buns, pretzels or fruit

• Cheese and Vegemite sandwiches or 2 minute noodles

• Radix Nutrition Ultra Meals or Styrkr BAR+ Protein Rice Bars

Carbohydrate Strategy: How Much, And What Kind

Carbohydrate is still the main fuel above an easy pace, but "right" for an ultra differs from marathon advice. Aim for 30–50g/hour as a realistic baseline, extending towards 90g/hour only if you've specifically gut-trained for it¹˒³. Finishers of 100-mile races average closer to 44g/hour – well below marathon-style targets, simply because it's harder to hit high rates many hours into a race¹.

Mixing glucose and fructose ("multiple transportable carbohydrates") lets your gut absorb more per hour without a proportional rise in GI distress – the reason most gels and drink mixes list both on the label²˒³.

Day to day in training, aim for 5–8g/kg/day of carbohydrate to avoid chronic glycogen depletion, even if you plan to race on a more fat-reliant strategy¹.

Protein & Fat: The Macronutrients Everyone Forgets

Protein → Aim for 5–10g/hour during racing. Finishers of ultra races consume roughly twice as much protein per hour as non-finishers¹. It may help offset central fatigue (see Section 6) and supports muscle repair. Day to day, spreading protein as roughly 20g every three waking hours supports muscle repair better than the same total in one or two large meals¹˒⁴.

Fat → Reliance on fat rises as races lengthen, and appetite shifts towards savoury, fattier foods – cheese, salami, nut butters – which also carry useful sodium¹. Some athletes train "fat-adapted" (higher fat, lower carb) to spare glycogen; keto-adapted ultra-runners show higher fat-oxidation rates, but evidence this translates to faster race times is still limited¹˒⁵. For most runners, leaning into whole, fat-and-protein-rich foods later in a race – without going fully low-carb – is the safer, better-supported approach¹˒².

Electrolytes & Avoiding Hyponatremia

Sweat losses over many hours can be substantial, and it's not just water – sodium, potassium, and magnesium go too. Under-replacing electrolytes is linked to cramping and nausea, but sweat sodium concentration varies several-fold between people, so a "one size fits all" dose rarely works¹˒⁶. Test your own sweat losses in training, practise your race-day drinks and electrolytes beforehand, and use a general-purpose product like Skratch Labs Sport Hydration Mix or Näak Ultra Energy Drink Mix as a starting point if you haven't dialled in your own numbers. A useful target is 500–700mg sodium per litre of fluid, with total intake around 450–750mL/hour, adjusted for heat, body size, and gut tolerance¹˒⁶.

The bigger risk is exercise-associated hyponatraemia (EAH) – a drop in blood sodium, usually caused by overdrinking rather than under-salting⁶. The strongest prevention is simple: drink to thirst, not by the clock, and don't assume more fluid is always safer⁶. EAH symptoms (headache, nausea, confusion) can mimic dehydration, which is exactly the danger – if in doubt, get medical help rather than drinking more⁶.

Mental Energy Matters: Fuelling The Brain, Not Just The Legs

Ultras are as much a mental game as a physical one. Steady blood glucose, good hydration, and specific brain-supporting nutrients all help fend off the "mental fog" that sets in late in a race¹˒².

One mechanism is the central fatigue hypothesis: during long exercise, rising tryptophan relative to BCAAs increases brain serotonin, which is linked to perceived fatigue. Protein or BCAAs during exercise may help offset this, alongside stable blood glucose – part of why some gels, bars and drink mixes include added BCAAs¹˒⁷.

Ketone esters come up in the same conversation, since the brain can use ketones as fuel when glucose runs low. Worth knowing about, not worth building a plan around – the ISSN position stand says the evidence for ketone esters improving ultra-marathon performance just isn't there yet¹.

Options worth trying → 226ERS High Energy Gel – Blackcurrant (contains BCAAs), deltaG (ketone ester), and Radix Nutrition Ultra Meals.

Caffeine: Using It Strategically

Caffeine is one of the better-supported performance aids in endurance sport, backed by strong meta-analytic evidence⁸. For ultras specifically, it's most valuable late in a race, especially when sleep deprivation in overnight events starts affecting alertness and decision-making¹.

Rather than front-loading it early, hold some caffeine in reserve – gels, chews, or aid-station coffee – for when you need it most, and test your dose in training first.

Putting It Together: A Sample Race-Day Fuelling Plan

Every athlete's needs differ with body size, pace, conditions, and gut tolerance, so use this as a starting template to adapt and test in training, not a fixed prescription¹:

• Hourly energy target: Roughly 200–400kcal/hour for events beyond 100km, and 150–300kcal/hour for shorter ultras (around 50 miles)¹.
• Carbohydrate: 30–50g/hour, moving towards 60–90g/hour later in training only once your gut has been trained to tolerate it¹˒³.
• Protein: 5–10g/hour, particularly from the mid-race point onwards.
• Fluid: Roughly 450–750mL/hour, adjusted to thirst and conditions – not a fixed number¹˒⁶.
• Sodium: 500–700mg/L in fluids during hot or prolonged efforts, plus salty whole foods as appetite shifts¹˒⁶.
• Food mix: Sweet options early (gels, dates, bananas, sports drink); savoury, fattier, more calorie-dense whole foods from the midpoint onwards¹.
• Caffeine: Held in reserve for the back half of the race or overnight sections¹˒⁸.

Take-Home Points

Ultra-marathon fuelling is a trained skill, not a race-day improvisation.

• Start gut training months out, not weeks

• Aim for 30-90g/hour of carbohydrate: 30-50g/hour as a baseline, up to 90g/hour only if you've specifically trained your gut for it

• Don't neglect protein and fat as the race lengthens

• Be deliberate about sodium, but let thirst set your drinking pace, not the clock - overdrinking is the bigger danger, not running low on salt

• Support the brain as well as the legs - BCAAs and, more speculatively, ketone esters - and keep caffeine in your back pocket for when you need it most

References

1. Tiller NB, Roberts JD, Beasley L, et al. International Society of Sports Nutrition Position Stand: nutritional considerations for single-stage ultra-marathon training and racing. J Int Soc Sports Nutr. 2019;16:50.

2. Nikolaidis PT, Veniamakis E, Rosemann T, Knechtle B. Nutrition in ultra-endurance: state of the art. Nutrients. 2018;10(12):1995.

3. Jeukendrup AE. Training the gut for athletes. Sports Sci Exch. 2017;28(178):1-6.

4. Areta JL, Burke LM, Ross ML, et al. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. J Physiol. 2013;591(9):2319-2331.

5. Volek JS, Freidenreich DJ, Saenz C, et al. Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism. 2016;65(3):100-110.

6. Bennett BL, Hew-Butler T, Rosner MH, Myers T, Lipman GS. Wilderness Medical Society clinical practice guidelines for the management of exercise-associated hyponatremia: 2019 update. Wilderness Environ Med. 2020;31(1):50-62.

7. Watson P. Nutrition, the brain and prolonged exercise. Eur J Sport Sci. 2008;8(2):87-96.

8. Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z. Wake up and smell the coffee: caffeine supplementation and exercise performance - an umbrella review of 21 published meta-analyses. Br J Sports Med. 2020;54(11):681-688.

Ash Miller
Dietitian and Nutritionist (Masters)
Bachelor of Physical and Health Education
Instagram: @ashthomo_nutrition

Disclaimer:
The content in this blog is for general information only and is not a substitute for professional medical advice, diagnosis, or treatment. Always speak with your doctor or allied health team before changing your diet, exercise, or taking supplements, especially if you have a health condition or take medication. Please use this information as a guide only. Aid Station doesn't take responsibility for individual outcomes.