A marathon fueling plan covers three windows: a carbohydrate-rich meal about three to four hours before the start at roughly 1 to 4 grams per kilogram of body weight, a top-up in the final hour, and 30 to 60 grams of carbohydrate per hour once racing. Those numbers come from the joint position stand of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine. Nothing in this article is a prescription, and individual plans should be rehearsed in training.
24 News Click publishes information, not medical advice. Runners with diabetes, gut conditions, or other medical concerns should plan race-day nutrition with a qualified clinician or sports dietitian.
What should a runner eat three to four hours before the start?
The pre-race meal exists to top off liver glycogen, which falls overnight and fuels the early kilometers. The joint position stand supports roughly 1 to 4 grams of carbohydrate per kilogram of body weight, eaten three to four hours before exercise, which for a 70-kilogram runner means somewhere between 70 and 280 grams of carbohydrate. In practice most runners settle on familiar, low-fiber foods: white rice, toast with honey, banana, oatmeal with little fat.
Fat, fiber, and heavy protein slow stomach emptying and raise the odds of mid-race gut trouble, which is a real problem in this sport. Surveys of marathon participants have found that a substantial share of runners report gastrointestinal symptoms during races, with higher rates among slower runners and those taking non-steroidal anti-inflammatory drugs, which research links to gut injury in endurance events.
Is anything needed in the final hour before the gun?
A small carbohydrate top-up in the last 30 to 60 minutes is supported by the evidence and by race-day logistics. Studies summarized in sports nutrition reviews show that eating carbohydrate in the hour before exercise raises blood glucose without harming performance, provided the amount is modest and practiced. A banana, a gel, or a sports drink fits.
One caution from older research: a large sugar dose shortly before hard exercise can, in some people, trigger reactive low blood sugar once insulin rises and running begins. Reviews note this effect is inconsistent and smaller with carbohydrate types like mixtures including fructose, which is another argument for rehearsing the exact plan in training rather than trying something new on race morning.
What happens at the starting line, hydration-wise?
The American College of Sports Medicine's fluid guidance supports starting exercise hydrated, with beverages at meal times before the race, and drinking to thirst or a planned schedule during. Overdrinking before the start is a genuine hazard: exercise-associated hyponatremia, a dangerous dilution of blood sodium, has been documented in slower marathon runners who drink more than they sweat, including well-known cases from major-city marathons in the early 2000s.
The safest evidence-backed pattern is modest drinking with early fluid stations, especially in warm weather, and stopping at signs of bloating. The Centers for Disease Control and Prevention maintains plain-language guidance on healthy hydration as general background.
How much carbohydrate is needed per hour during the race?
For events longer than about an hour, the joint position stand recommends 30 to 60 grams of carbohydrate per hour, typically from gels, sports drinks, or bananas. Research on carbohydrate transport explains the ceiling: glucose alone is absorbed through one intestinal transporter, saturating near 60 grams per hour.
For very long efforts beyond roughly two and a half hours, work by Asker Jeukendrup and colleagues showed that mixing glucose and fructose, which use different transporters, allows oxidation of up to about 90 grams per hour in a roughly 2-to-1 ratio. Marathons sit at the edge of that window; elite runners, who finish near two hours, use less, while four- and five-hour runners may benefit from practicing larger intakes, with gut training over weeks.
What about caffeine on race morning?
Caffeine has among the strongest evidence bases in sports nutrition. A 2019 meta-analysis by Grgic and colleagues, pooling dozens of trials, found caffeine ingestion improves endurance performance, with typical study doses around 3 to 6 milligrams per kilogram of body weight taken about an hour before exercise. A smaller dose taken mid-race is also supported in some trials.
Caffeine is a stimulant with individual responses and sleep consequences, and it is banned only above urine thresholds set by the World Anti-Doping Agency, thresholds nearly impossible to reach from coffee. Runners who rarely use caffeine should not debut it on race day, since anxiety and gut upset are common early side effects in the research.
Should anything change in the final 10 kilometers?
Not much changes except the margin for error. Late-race intake still helps: muscle takes up carbohydrate even in the closing stages, and blood glucose is a fuel source that spare glycogen cannot cover by that point. Practical constraints grow, since gut blood flow falls and tolerance drops at higher effort.
This is why the timeline matters more than any single product. A runner who has rehearsed a gel every 30 to 40 minutes with water through training builds both gut tolerance and habit, and the final kilometers simply continue the schedule rather than improvising it. Reviews of marathon nutrition consistently rank new race-day foods among the most common self-inflicted problems.
What does the evidence not show?
The evidence does not show one universal timeline. It shows ranges that shift with body size, weather, pace, and gut tolerance. It also does not show benefits from exotic race-week or race-morning practices sometimes marketed to runners, such as aggressive single-day loading protocols without prior training of the gut, which have thin support in controlled trials.
What should the week before the race look like?
Race-day fueling sits on top of a fueling week. Reviews of marathon preparation support a moderate carbohydrate increase over the final one to three days, around 8 to 10 grams per kilogram per day in combination with tapering training, so glycogen stores arrive at the start line full. Hydration gets similar treatment: normal drinking with meals, plus a little extra salty food or sodium-containing drink in hot conditions.
The final two days also restrict the experiments. New restaurants, high-fiber loads, and unfamiliar drinks are common culprits in race-week gut problems reported in athlete surveys. The research literature on marathon nutrition repeatedly makes the same point in different words: the race-day timeline only works if every item on it has been rehearsed in long training runs, from the breakfast itself to the gel flavors at kilometer 30.
FAQ
What should a runner eat the morning of a marathon?
A familiar, carbohydrate-focused meal three to four hours before the start, in the range of 1 to 4 grams per kilogram per the joint position stand: common choices are toast with honey, banana, oatmeal, or white rice. Low fiber and low fat reduce gut trouble during the race.
Can a runner rely on sports drinks alone during a marathon?
Partly. Race-station drinks typically supply carbohydrate and fluid together, but the carbohydrate dose per hour often falls below the 30 to 60 gram research range unless gels or other food supplement it. A written per-hour plan worked out in training is safer than estimating at aid stations.
How do runners avoid hitting the wall?
The wall reflects glycogen depletion. Evidence-backed reduction comes from adequate carbohydrate in the days before, a proper pre-race meal, and 30 to 60 grams per hour during the race, with higher intakes up to about 90 grams per hour of mixed carbohydrate for very long efforts in gut-trained runners.
For more context, read Carbohydrate loading: what the evidence says about old and new protocols.
For more context, read what to eat before morning training.
For more context, read Carbohydrate periodization: what endurance athletes need.