From 5K to Ultra Marathon
There’s incredible wisdom in the adage, “Nothing new on race day.” When it comes to race nutrition, you should practice your race-day food and fluid strategy during your training.
Your nutritional needs depend highly on your metabolism, food tolerance, and preferences. They can also vary based on the type of event you participate in (e.g., short, long, or ultra distance; trail or road; running, cycling, or triathlon) and on the conditions (e.g., heat, elevation, etc.).
The guidelines in this article encourage high-carb availability for your race to promote optimal performance. However, if you are fat-adapted, the suggested carb intake might be too high for your metabolism. That’s why practicing your nutritional intake during training sessions or less important races is important. Testing your strategy allows you to gauge your body’s response and adjust to your individual needs.
A recent study analyzing the nutritional intake of 11 trail runners during competition observed an average carb intake of 14.93 g/h, 146.42 mg/h for sodium, and 399.73 mL/h for water, which was lower than the current scientific recommendations for carb and sodium, while at the same level for water.1You should see those guidelines as a starting point but adapt them to your experience through trial and practice. Always start with a lower dosage, and increase progressively as you practice, always basing adjustments on your personal gut tolerance. Consistent practice will encourage GI adaptations, allowing you to increase your carb intake and achieve better performance without GI discomfort.
Refer to Figure 1 – Macronutrient and Fluid Intake Recommendations For Endurance Training, Event Fueling, and Recovery for a helpful summary.
You can also seek guidance from a nutrition professional to help establish your ultimate race nutrition strategy.
For events lasting less than 90 min, we recommend replenishing your muscle and liver glycogen stores by consuming a carb-rich diet the previous day with a minimum of 6 g/kg and up to 7-12 g/kg of carbs.2,3
For events lasting more than 90 min, “carb loading” is recommended 36 to 48 hours before the competition. For effective loading, you should consume 8-12 g/kg of carbs per day with an exercise taper.2,3,4 Select carb-rich foods and fluids that are easily digestible to ensure your fuel targets are met. You don’t need to eat more than usual; instead, adjust your diet to include more starches and sugars while cutting back on protein and fat. Good carbs include bread, pasta, rice, potatoes, fruit juices, smoothies, jams, honey, or energy bars. Be careful with your pre-race dinner, avoiding fiber, fat, or spices that may cause gut discomfort during your race. Do not improvise at the last minute! Try your pre-race dinner during your training, ideally the night before a long run.
Endurance events typically start early in the morning, so your liver glycogen will be slightly depleted following an overnight fast. To prepare for this, we recommend topping off your liver glycogen by consuming 1–4 g/kg of carbs 1-4 hours before your event.2,3
Again, you may want to practice your pre-race breakfast during your training, so you can find what works best for you. You should limit fat and fiber, no matter what you choose, while still getting enough nutrition density. The best options include oatmeal and banana (if you can handle some fiber and eat your breakfast early enough to allow digestion), low-fiber bread with jam or honey, a fruit and protein powder smoothie, or a sports drink. To be adequately hydrated before your race, drink 0.5L of water 1-2 hours before the race.
Approximately 30 minutes before your race, you may want to sip on a hydration drink, preferably one that’s low in carbs and high in electrolytes. You can also eat some gel, half an energy bar, gel, or a few chews 10-15 minutes before the start.
Fueling recommendations per event duration
If your event lasts less than 45 minutes, there is no need for any carb intake during your race. Your glycogen stores will be enough to fuel your effort.
If your event lasts between 45 and 75 minutes, you will probably perform at a relatively high intensity and benefit from some carb intake or a carb mouth rinse to achieve better performance.
Studies have shown that carb mouth rinses without actual ingestion during endurance exercise can stimulate parts of the brain and central nervous system and reduce perceived exertion and increase performance.2,4,5 Frequent carb mouth rinses (every 5-10 minutes) instead of fueling can elicit reliable performance gains without adverse GI symptoms.5
If your event will last more than one hour, you will need to adopt a fueling strategy to maintain your carb availability.
For an event lasting 1 to 2.5 hours, experts recommend consuming 30-60 g/hour to maximize glycogen sparing. The longer the event, the higher your carb intake should be. 30 g/hour should be sufficient for events lasting around one hour, but you should target 60 g/hour for events closer to two hours.
You should choose carbs that are absorbed and oxidized rapidly, such as glucose, sucrose, or maltodextrin. You can choose between liquids or solids — sports drinks, gels, or low-fat, low-protein, low-fiber energy bars work well. If you decide to replenish with liquids, you can reach the proper levels by sipping a homemade or commercial sports drink every 15 minutes.2,3,4
For an event lasting more than 2.5 hours, a higher carb intake from 60-90 g/hour will give you optimal performance. The upper limit depends on whether you consume a single carb source or a mix.
If you consume a single type of carb (e.g., glucose, sucrose, or maltodextrin), even though those carbs can be absorbed quickly, they cannot be oxidized at a higher rate than 1.0-1.1g/minute. Due to this, there’s no point in consuming more than 60 g/hour.
Your strategy should change if you consume a carb mix like glucose and fructose, maltodextrin and fructose, or glucose, sucrose, and fructose. Glucose and fructose are absorbed via different intestinal transporters (SGLT1 and GLUT5, respectively), which means more carbs will be absorbed, resulting in higher oxidation rates (about 1.2–1.3 g/minute). As a result, carb combinations are often better tolerated by the gut. As such, we advise consuming a carb mix of up to 90 g/hour to achieve optimal carb availability for an event longer than 2.5 hours.
With such high-carb intakes, you want to routinely practice your fueling plan during training or less important races to assess your GI comfort and the type of carbs you tolerate best (solid, gel, liquid, or a combination).2 By practicing your fueling strategy regularly, you will enable GI adaptations that optimize carb absorption and mitigate GI distress, allowing you to increase your carb intake gradually.
For events lasting more than 6 hours (ultramarathons and Ironman races), your nutrition goal goes beyond achieving optimal performance. It focuses on minimizing your calorie deficit and keeping you hydrated to sustain the long hours and finish strong.
You should aim to consume 150-400 Kcal/hour with 30-50 g/hour of carbs and 5-10 g/hour of protein and fat. You can get these nutrients from various calorie-dense foods (savory foods are ideal for longer races) and drink 450-750 mL/hour (or 150–250 mL every 20 minutes) of fluids combined with electrolytes. If the weather conditions are hot and humid, you should monitor your electrolyte and sodium intake and aim at ingesting 500-700 mg/L of sodium.
GI distress is common in longer races and is often a cause of non-completion. Progressive gut training during your training is critical to avoid GI problems during the race. If you are still susceptible to GI discomfort after gut training, you may want to try a short-term low-FODMAP diet (fermentable oligo-, di-, monosaccharide, and polyol) for 3-6 days before and during your race. Avoiding those types of carbs may help alleviate your symptoms. If you experience GI distress during the race, avoid highly concentrated carbs while maintaining a minimal calorie intake of 200 Kcal/hour and minimizing dehydration.
If you want to take supplements during your race, small caffeine doses (1-2 mg/kg, or 70-140 mg for a 70 kg athlete) have proven beneficial, especially in the latter stages of longer events (> 24 h) when sleep deprivation may impair your performance and compromise your safety. However, data that supports other supplements, such as ketone esters, MCTs, or vitamins, are limited.6
The recommended fluid intake during a race is typically between 400-800 mL/hour, regardless of the event type and duration. However, the ideal intake depends on the athlete’s physical variations (e.g., sweat rates, sweat sodium content, exercise intensity, body temperature, body weight, kidney function) and race conditions (e.g., humidity, environmental temperature, etc.). You should identify your hydration needs during practice by monitoring your urine color (it should be pale yellow) and checking your body weight pre- and post-exercise. With that data, you can customize your race fluid intake based on your experience.2
While it is critical to stay well hydrated during your event, drinking too much dilutes sodium levels in the blood and can result in a dangerous medical condition called hyponatremia. You should complement your fluid intake with electrolytes (sodium, potassium, calcium, magnesium, and chloride) to compensate for the electrolytes lost in sweat. Sodium intake, in particular, should be between 300-600 mg/hour (1.7–2.9 g salt). As for total fluid intake, those numbers are specific to each individual and should be customized based on your own experience.2
Good nutrition after your race is critical for better recovery. You want to refuel, replace muscle glycogen, and provide protein for muscle building and repair. You may eat a light meal right after your race or opt for a recovery snack (e.g., your favorite drink or bar containing a mix of carbs and protein) when you finish. Whichever option you choose, you should follow it with a full meal within two hours after your event. Enjoy your recovery meal, and make sure it contains carbs, protein, and vegetables. You should also drink enough water to replace approximately 150% of the fluid you’ve lost based on your body weight.
This article concludes our series on optimal race nutrition. Hopefully, you are better informed on how your nutrition can influence your performance and better equipped to implement your own nutrition strategy for your upcoming training and events. As always, we are here to assist you throughout this process. Please reach out with any questions. Our team can work with you to customize a nutrition plan that will best support your training, your races, and your health.
- Jiménez-Alfageme R, Aguirre López L, Mielgo-Ayuso J, Martínez Sanz JM. Análisis de la ingesta nutricional en corredores de montaña durante una prueba deportiva [Analysis of nutritional intake in trail runners during competition]. Nutr Hosp. 2021;38(2):321-327.
- Vitale K, Getzin A. Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients. 2019;11(6):1289. Published 2019 Jun 7. doi:10.3390/nu11061289
- Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine joint position statement. Nutrition and athletic performance. Med Sci Sports Exerc. 2016;48(3):543-568.
- Casazza GA, Tovar AP, Richardson CE, Cortez AN, Davis BA. Energy availability, macronutrient intake, and nutritional supplementation for improving exercise performance in endurance athletes. Curr Sports Med Rep. 2018;17(6):215-223.
- Getzin AR, Milner C, Harkins M. Fueling the triathlete: Evidence-based practical advice for athletes of all levels: Evidence-based practical advice for athletes of all levels. Curr Sports Med Rep. 2017;16(4):240-246.
- 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(1):50.