Introduction: Why Nutrition Is the Fourth Discipline of Ultra Running
In triathlon, athletes speak of swimming, cycling, and running as three disciplines — but experienced competitors know that nutrition is the unofficial fourth discipline that determines whether the other three come together successfully or collapse spectacularly. Ultra marathon running is no different. For events lasting six hours, twelve hours, twenty-four hours (as contested at the Commonwealth Mountain & Ultra Distance Running Championships 24-hour race in Anglesey), or longer, nutrition management is not a peripheral concern but a central performance determinant. Get it right and you can maintain consistent performance for extraordinary durations. Get it wrong and you will experience the bonk, GI distress, or complete energy collapse that ends so many ultra race dreams.
Understanding Energy Systems in Ultra Running
Ultra running at sustainable pace draws primarily on aerobic metabolism, which can utilise both carbohydrates and fats as fuel. At lower intensities, fat oxidation contributes significantly to energy supply — a trained ultra runner can oxidise fat at rates that provide 300-500 calories per hour without additional carbohydrate intake. However, as intensity increases (on steep climbs, during race surges), carbohydrate becomes the dominant fuel, and carbohydrate stores (glycogen) are finite — approximately 2,000 calories’ worth in a well-fuelled athlete. The fundamental nutrition challenge of ultra running is managing this energy system interplay: preserving glycogen through moderate intensity management while ensuring adequate carbohydrate intake to fuel higher-intensity efforts.
Pre-Race Nutrition: Loading for Performance
Carbohydrate loading — strategically increasing carbohydrate intake in the two to three days before a race to maximise glycogen stores — is an evidence-based strategy for endurance events lasting more than 90 minutes. Practical carbohydrate loading involves consuming 8-10 grams of carbohydrate per kilogram of body weight per day for two to three days pre-race, typically by increasing portion sizes of rice, pasta, bread, oats, and potatoes rather than dramatically changing your diet. The morning of your race, a familiar, easily digestible breakfast consumed two to three hours before the start — oats, toast, banana, and modest amounts of protein — tops up glycogen stores without risking GI distress during the early stages of racing.
During-Race Fuelling: The Golden Rules
Three golden rules govern during-race nutrition for ultra runners. First: eat early and eat consistently — beginning to consume carbohydrates within the first 30-45 minutes of racing, before you feel hungry, prevents the glycogen depletion that causes energy crashes. Second: target 60-90 grams of carbohydrate per hour for sustained ultra efforts (some trained athletes can process up to 120g/hr using multiple carbohydrate sources). Third: eat real food whenever possible — the combination of fat, fibre, and protein in real food options (boiled potatoes, rice balls, dates, peanut butter sandwiches, broth) provides sustained energy and reduces the flavour fatigue that makes sweet gels increasingly unappealing as ultra races extend beyond six to eight hours.
Hydration Strategy: More Complex Than You Think
Hydration management in ultra running is significantly more nuanced than the simple instruction to drink regularly. Hyponatremia — dangerously low blood sodium caused by excessive plain water intake without sufficient sodium replacement — is a genuine medical risk in long ultra events, particularly among slower runners who have extended time on course in warmer conditions. The current evidence-based guidance is to drink to thirst rather than to a rigid schedule, while ensuring consistent sodium intake throughout the race. Sodium can be obtained through salty foods (pretzels, crisps, broth, electrolyte tablets), which also help stimulate appropriate thirst signals. In hot conditions, sweat rates increase significantly and fluid and sodium needs rise correspondingly.
Managing Gastrointestinal Issues on the Run
GI distress is one of the most common causes of DNF (did not finish) in ultra marathon events, affecting up to 90% of ultra runners to some degree. Causes include: high-fat or high-fibre foods consumed too close to racing, dehydration concentrating the gut contents, reduced gut blood flow during hard effort, stress hormones activating gut motility, and mechanical jostling of gastric contents during running. Prevention strategies include: testing all race nutrition in training under similar conditions, avoiding unfamiliar foods in the 24-48 hours before a race, having a backup nutrition plan for when primary foods become unpalatable, eating smaller amounts more frequently rather than large infrequent feeds, and managing race pace to avoid intensities that divert blood flow away from the gut.
Caffeine: The Legal Performance Enhancer
Caffeine is one of the most thoroughly researched and clearly effective ergogenic aids in endurance sport. For ultra runners, strategic caffeine use can meaningfully extend performance, improve alertness during nighttime running sections, and help manage the perception of effort during the most demanding race phases. The evidence-supported dose for performance enhancement is 3-6 milligrams of caffeine per kilogram of body weight, consumed 45-60 minutes before the intended benefit window. In ultra races, many runners save their caffeine for the middle or final third of the race when fatigue and sleepiness become significant factors, rather than using it early when alertness is naturally higher. Coffee, caffeine gels, and caffeine chews all provide effective delivery mechanisms.
Recovery Nutrition: The 30-Minute Window
Post-race nutrition is as important as race-day fuelling for the ultra runner’s medium-term recovery and ability to return to training. The metabolic window immediately after finishing — typically described as 30-45 minutes — represents a period of heightened insulin sensitivity and increased muscle protein synthesis during which nutrient delivery produces significantly greater recovery effects than at other times. A recovery meal or shake providing 20-40 grams of high-quality protein and 60-100 grams of carbohydrate, consumed within this window, initiates muscle glycogen replenishment and protein synthesis that form the foundation of physical recovery. Many ultra runners are too nauseated or fatigued to eat solid food immediately post-race — liquid nutrition (protein shakes, chocolate milk, recovery drinks) provides an effective alternative.
Individualising Your Nutrition Plan
The most important principle in ultra running nutrition is individuality. General guidelines provide a starting framework, but every runner has different sweat rates, different gut tolerance, different carbohydrate processing capacity, and different flavour preferences during extended exercise. The only reliable way to discover your individual nutrition profile is through systematic experimentation during training. Long training runs — particularly back-to-back long runs that simulate ultra fatigue — provide the best opportunity to test nutrition strategies under conditions that approximate race demands. Keeping detailed training nutrition logs that record what you ate, when, how your energy felt, and any GI issues, builds the personalised database that will inform your optimised race-day nutrition plan.
Conclusion: Fuel Your Journey to the Finish Line
Ultra marathon nutrition is a discipline that rewards investment and experimentation. The athletes who perform best over extreme distances are invariably those who have spent as much time developing their nutrition strategy as their physical fitness. Whether you are preparing for your first 50-kilometre trail race or targeting a 24-hour track event like the Commonwealth Championships, applying the principles in this guide — with the personalisation that only training-based experimentation can provide — will give you the nutritional foundation to perform to your potential and enjoy the extraordinary experience of ultra distance running.