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LOGINMarathon fueling: get it right, before, during and after
SPB looks at new research on real-life marathon fueling by recreational runners, and makes recommendations on how runners can improve their pre-, in- and post-race nutrition
Over the past 30 years or so, a large body of research has accumulated showing that consuming carbohydrate while on the move (eg gels, carbohydrate drinks etc) can significantly enhance performance over longer-duration (90+ minutes) events. The explanation is simple and twofold:
1. Carbohydrate is the muscles’ premium fuel during exercise because carbohydrate can be absorbed and broken down to release energy efficiently and rapidly.
2. Due to the biochemistry of carbohydrate oxidation, more energy can be liberated per litre of oxygen consumed compared to fat. That makes carbohydrate the best fuel for meeting the energy demands of muscles when exercise intensity becomes very high and when oxygen is scarce (because you are at or near your maximum oxygen uptake limit - also known as ‘VO2max’).
Much of the carbohydrate oxidized for fuel during exercise is derived from stored carbohydrate in the muscles (muscle glycogen). Research shows that even a modest drop in the levels of muscle glycogen can produce feelings of fatigue and tiredness, which is why a large body of research has demonstrated that keeping topped up with carbohydrate during prolonged exercise can help stave off fatigue(1-9). It’s for this same reason (to top up your muscle glycogen) that sports scientists recommend a triple-whammy approach to fueling for an endurance event and for superior recovery after an event. This approach is as follows:
· Pre-event fueling - Ensure that you consume plenty of carbohydrate in the days leading up to a big event such as a distance ride, running marathon or longer-distance triathlon (sometimes referred to as ‘carbohydrate loading’, which you can read more about the theory and practice of carbohydrate loading in this article). Additionally, researchers have suggested that in the hours prior to an event, athletes consume pre-exercise protein intake at around 0.3 grams per kilo of bodyweight (depending on gastrointestinal tolerance) in order to help offset the significant muscle breakdown that can occur during a race, particularly in running events(10). Regarding pre-race fat intake, athletes should limit high-fat foods to avoid GI discomfort.
· In-race fueling - a large body of research has established that in-race carbohydrate fueling can prolong endurance performance. Recent data suggests that a good rule of thumb is as follows (see figure 1)(10): for events lasting less than 60 minutes, no carbohydrate ingestion is required; for activities lasting over 60 minutes, an active fueling strategy is recommended to maximize performance and that when events last 60-150 minutes, athletes should consume 30–60 grams of carbohydrate per hour, using a 6–8% solution (concentrations typically found in commercial sports drinks); for events lasting over 150 minutes, higher carbohydrate intakes of 60–70 grams per hour up to 90 grams per hour (if tolerable) can give improved performance, ideally consumed every 10–15 min to maximally spare glycogen stores; at the highest levels of intake, multiple transport carbohydrates – ie glucose/fructose drinks and gels – are recommended for easier absorption (see this article for a more in-depth look at carbohydrate type).
· Post-race fueling - Post-exercise carbohydrate consumption continues to be a very important nutritional strategy, as it is essential to speed recovery. Research shows that consuming 0.8–1.0 grams of carbohydrate per kilo of bodyweight per hour following exercise results in higher replenishment of glycogen stores(11). Additional research indicates that the addition of 0.3 or more grams protein per kilo of bodyweight per hour can also be beneficial for enhancing glycogen resynthesis and promoting muscle synthesis to compensate for muscle tissue loss during exercise(10). Furthermore, it is recommended to replace fluid loss by consuming water or hydration drinks equivalent to 150% of the pre-post bodyweight lost(10). For example, if you lose 1kg of bodyweight as a result of exercise, the recommendation is to consume 1.5kgs (ie 1.5 litres) of fluid in the hours after exercise.
Figure 1: Summary of carbohydrate intake recommendations by event duration
Actual nutritional practice in marathon runners
The method of optimizing nutritional intake before, during and after endurance competition such as marathon running has been well established in dozens of peer-reviewed studies. Surprisingly however, despite the popularity of marathon running, little is known about the actual nutrition practices in runners, especially when it comes to recreational runners who don’t on the whole have access to coaches and trainers. In particular, despite the fact that an optimum carbohydrate intake is known to be positively associated with faster running times(12,13) consuming adequate/optimum amounts during the race is often a real challenge for endurance athletes because of the occurrence of gastrointestinal symptoms (abdominal pain, cramps, bloating, nausea etc)(14). Moreover, the few studies that have investigated dietary intakes in endurance athletes have primarily focused on the intake during the event – not before or after(15,16). However, a newly published study by a team of Spanish and British researchers has provided a valuable insight by examining the dietary intakes of marathon runners before, during and after a race to determine whether/how the runners’ nutritional practices predicted finishing times independently of the age and sex of participants.
What they did
In the study, which was published in the journal ‘Sports Medicine – Open’, researchers investigated the consumption of liquids, food, and supplements in 160 runners who participated in the 2022 Seville marathon(17). The marathon runners averaged 42.2 years old and were comprised of 87.5% men and 12.5% women. All participants had competed in regional, national, and international competitions for at least two years and had not suffered from any injuries or illnesses in the six months prior to the survey.
To carry out this investigation, fluid, food, and supplement intake, as well as the incidence of gastrointestinal complaints in endurance competitors before, during and after the 2022 Seville Marathon were collected using a validated online self-administered questionnaire known as the ‘Nutritional Intake Questionnaire for Endurance Competitions’(18). This questionnaire includes 50 questions divided into five specific sections:
· Socio-demographic factors.
· Sports data.
· Food, liquid, and supplement intake one hour before, during, and one hour after the race.
· Gastrointestinal symptoms.
· Dietary/nutritional planning carried out by the runners.
The coding of the variables and the estimation of energy, macronutrients and any sports supplements consumed was carried out by a trained sport dietician using the Spanish Database of Food Composition. The relationship between marathon finishing time, training characteristics, and the runners’ pre-competition and during-competition nutritional intake were then statistically evaluated to show how these factors impacted marathon finishing time – in particular, the impact of fluid, energy, carbohydrate, and sodium intake before and during marathon.
What they found
The key findings were as follows:
· Most of the runners followed a nutrition plan for the race; of these runners, (46%) did not receive nutritional advice and planned their own nutrition, while among those who did receive advice, 19% received it from a trainer or coach and another 19% followed recommendations by a sports body.
· Carbohydrate intake prior, during and post competition ranged from 23 grams to 100 grams per hour. Among runners who ingested carbohydrate one hour prior to the race, approximately 56 grams were ingested from drinks and gels and 42 grams from solid foods.
· During the marathon, athletes ingested around 35 grams of carbohydrate from drinks, 101 grams from gels, and 25 grams from solid foods.
· After competition, athletes consumed an average of 40 grams of carbohydrate from drinks, 14 grams from gels, and 30 grams from solid foods.
· The key finding: athletes who met the recommend intake for carbohydrate intake (60-90 grams per hour) during the competition were much more likely to finish the marathon in less than 180 min. This finding was independent of the runners’ sex, age or experience.
· Post-race carbohydrate intake reached the recommended value but post-race protein intake did not meet the minimum recommended 0.3 grams per kilo per hour for protein, with runners averaging just 0.1grams/kg/hour.
· Regarding gastrointestinal complaints, only the 13.4% of the runners reported any discomfort, the most frequent being belching, wind or tummy pain.
· The intake of fluid averaged 466mL per hour, which is at the lower limit of recommendations for mild-warm weather (the temperature hovered around 19C (66F).
Implications for runners
In their summing up, the researchers highlighted the fact that many runners fell short of the recommended in-race carbohydrate intake, and that this shortfall was directly correlated to the likelihood of not being able to run a sub 3-hour marathon. In short, for recreational runners who are trying to break the 3-hour barrier, consuming the recommended 60-90 grams per hour of carbohydrate is a critical element of any successful plan! The key of course is to experiment during training and find out which feeding regime (frequency, quantity, drink type etc) capable of delivering that amount works for you. In-race fluid intake was also slightly down on recommended values, but if more carbohydrate is consumed as a drink, this is easily resolved.
One positive finding across the board was that only 13% of runners report gastrointestinal distress during the race. This may be due to the fact that many runners reported planning their own nutrition ahead of the race, which means they would have been practicing it in advance of the race. However, the low incidence of gastric distress may also be down to the fact that many runners fell short of the 60-90 grams per hour target for carbohydrate intake. While most of these runners will likely be able to up their carbohydrate intake without inducing gastric distress, there may be some who struggle in this respect. Again, practicing carbohydrate feeding during training is key. Finally, most runners fell very short of the post-race protein intake recommendations (3 grams/kilo/hour) – only reaching a third of the recommended amount. While not impactful on race performance, it’s probable that many of these runners are also falling short of post-exercise protein intake following their regular training sessions. This is less than ideal because post-exercise protein consumption is vital for recovery and muscle repair (see this article) so runners should try and ensure these needs are met!
References
1. Sports Med 1992; 14: 27–42
2. Metabolism 1996; 45: 915–921
3. Am J Physiol Endocrinol Metab 1999; 276: E672–E683
4. Med Sci Sports Ex 1993; 25:42-51
5. Int J Sports Med 1994; 15:122-125
6. Med Sci Sports Ex 1996; 28: i-vii
7. J Athletic Training 2000; 35:212-214
8. Int J Sports Nutr 1997; 7:26-38
9. Nutrition Reviews 1996; 54: S136-S139
10. Nutrients. 2019;11(6):1–20.
11. J Appl Physiol. 1988;64(4):1480–5
12. Med Sci Sports Exerc. 2012;44(2):344–51
13. Int J Environ Res Public Health. 2020;17(16):1–17
14. Sport Med. 2014;44(Suppl.1):79–85
15. Nutr Hosp. 2021;38(2):321–7
16. J Sports Sci. 2018;36(3):333–9
17. Sports Med Open. 2025 Mar 16;11:26
18. Nutrients. 2023;15(8):1–14
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