Carbohydrates for long-distance events: how many grams per hour and what to eat during a marathon
The joint position stand of ACSM, the Academy of Nutrition and Dietetics, and Dietitians of Canada recommends 30–60 g of carbohydrates per hour for exercise lasting 1 to 2.5 hours, and up to 90 g per hour for longer durations. These values are tied to exercise duration and can be converted into common foods.
How many carbohydrates per hour according to recommendations
The primary source is the position stand “Nutrition and Athletic Performance” (Thomas, Erdman, Burke, 2016), published in Medicine & Science in Sports & Exercise and Journal of the Academy of Nutrition and Dietetics. The table it contains links intake to exercise duration:
| Duration | Recommendation |
|---|---|
| Up to 45 minutes | Not needed |
| 45–75 minutes | Small amounts, including mouth rinsing |
| 1–2.5 hours | 30–60 g per hour |
| More than 2.5–3 hours | Up to 90 g per hour |
A marathon lasting more than 2.5–3 hours falls into the last row. However, “up to 90” indicates a ceiling, not a standard requirement. In Jeukendrup’s review (Sports Medicine, 2014; link), this amount is tied specifically to endurance competitions, and for low-intensity efforts, lower intakes are advised: for a runner finishing in five hours, 90 g per hour may approach or even exceed their total carbohydrate expenditure. The same review notes that carbohydrate recommendations do not depend on body weight.
The same figures appear in Burke et al.’s review (Journal of Sports Sciences, 2011; link): 30–60 g per hour suit longer-duration sports, while exceeding 2.5 hours may benefit from up to 90 g per hour.
Why a glucose-fructose blend
A single carbohydrate type, such as glucose, is absorbed via one intestinal transporter, which becomes saturated at roughly 60 g per hour. Fructose uses a different pathway, so a blend is required at higher doses. In studies analyzed by Jeukendrup (2014 review), glucose or maltodextrin combined with fructose in a 2:1 ratio was used. According to a 2017 review, consuming only one carbohydrate type above 60 g per hour increases the likelihood of gastrointestinal issues.
What this looks like in foods
Calculations are based on USDA FoodData Central (SR Legacy dataset) and verified by script. Serving sizes and weights come directly from the database.
| Food | USDA serving | Carbohydrates per serving | For 30 g | For 60 g |
|---|---|---|---|---|
| Banana | medium, 118 g | 27 g | about 130 g, one banana | about 260 g, two bananas |
| Seedless dark raisins | small box, 43 g | 34 g | about 38 g | about 76 g |
| Honey | tablespoon, 21 g | 17 g | about 36 g, two tablespoons | about 73 g, three to four tablespoons |
| Medjool date | one fruit, 24 g | 18 g | about 40 g, two fruits | about 80 g, three fruits |
| White bread | slice, 29 g | 14 g | about 61 g, two slices | about 121 g, four slices |
In the database, raisins, dates, and honey contain roughly equal proportions of glucose and fructose; bananas have slightly less fructose, and bread consists mainly of starch. The studies underpinning these recommendations used beverages and sports products; little is said about whole foods, so it cannot be assumed that bananas or bread yield the same effect at 90 g per hour.
Sports gels are not included in SR Legacy; their carbohydrate content must be calculated from package labels, which specify both serving size and carbohydrate amount. Source: USDA FoodData Central, accessed October 1, 2026.
Gut training
Jeukendrup’s review “Training the Gut for Athletes” (Sports Medicine, 2017; link) reports that gastrointestinal issues regularly affect 30–50% of athletes. Causes are largely unknown and individual, but frequency correlates with fiber, fat, and highly concentrated carbohydrate solutions.
The gut adapts. According to the same review, in a 28-day study by Cox et al., the group consuming a higher proportion of carbohydrates both in their diet and during training showed greater oxidation of ingested carbs. Effects on gastric emptying were observed in some studies after just three days of dietary modification. The 2014 review recommends practicing race-day nutrition strategies during training to reduce discomfort risk. The author notes that human data remain limited.
In practice, this means recording what and how much was consumed during long workouts and noting gut responses. A nutrition and running log works well for this.
Water and sodium
Per ACSM guidelines, fluid intake should match sweat losses, not exceed them: overdrinking is identified as the primary cause of hyponatremia. Sodium is needed when losses are high—during heavy sweating, salty sweat, or efforts longer than two hours. Exact amounts depend on the individual and weather conditions and should be determined during training. More details are in the article on water and electrolytes.
Carbohydrate loading
ACSM guidelines associate carbohydrate loading with events longer than 90 minutes: the table specifies 36–48 hours of elevated carbohydrate intake, while the text mentions tapering training before race day. This serves as a general reference, not a prescriptive meal plan; individualized plans are to be developed by a registered dietitian. Daily carbohydrate needs are covered in how many carbohydrates per day, and pre-exercise eating in pre-workout nutrition.
What not to try on race day
- Unfamiliar gels, bars, or drinks: tolerance should be tested in training.
- New foods the night before or morning of, plus high-fiber or high-fat meals shortly before the event: these are linked to gastrointestinal complaints.
- Higher-than-usual carbohydrate doses: the gut adapts gradually.
- Drinking “just in case” beyond actual sweat losses.
For specifics on fueling during workouts lasting 1.5+ hours, see carbohydrates for endurance.
When a doctor decides
Diabetes—especially when managed with insulin or glucose-lowering medications—heart disease, pregnancy, and gastrointestinal disorders alter both energy expenditure and safe fueling strategies, as well as carbohydrate response during exercise. In these cases, carbohydrate amounts, fluid intake, and permissible exertion levels must be coordinated with a physician; insulin users should consult an endocrinologist. This article outlines recommendations for healthy athletes and does not replace medical advice.
Frequently asked questions
- How many carbohydrates per hour are needed for a marathon?
- According to the joint position of ACSM, the Academy of Nutrition and Dietetics, and Dietitians of Canada (2016), 30–60 g per hour is recommended for exercise lasting 1 to 2.5 hours, and up to 90 g per hour for longer durations. For low-intensity exercise, Jeukendrup’s review (2014) suggests lowering these recommendations.
- Why mix glucose and fructose?
- Glucose is absorbed via a single transporter that becomes saturated at approximately 60 g per hour. Fructose uses a different pathway, so a mixture is required at higher doses; studies used a 2:1 ratio.
- Can I use a banana, raisins, and honey instead of a gel?
- Their carbohydrate content is based on USDA data: an average banana contains about 27 g, a small box of raisins about 34 g, and a tablespoon of honey about 17 g. The studies underpinning the recommendations used sports drinks and commercial products, with little specific information on whole foods.
- How to train your gut to eat while running?
- Practice your nutrition strategy during training: Jeukendrup’s 2017 review shows that the gut adapts, and the 2014 review recommends pre-training your nutrition intake to reduce the risk of gastrointestinal discomfort. Human data remain limited so far.
- Who should not follow these guidelines independently?
- Individuals with diabetes—especially those on insulin—heart conditions, pregnancy, or gastrointestinal disorders should consult a physician regarding carbohydrate intake and fluid consumption during exercise. According to ACSM guidelines, a registered dietitian develops an individualized nutrition plan.
Read next
- Carbohydrates during long workouts: when food is needed during exercise — Gels, isotonic drinks, and bars on the course solve one problem — preventing fuel from running out where it is truly needed.
- How many carbs do you need per day? — For an illustrative 2,000-calorie diet, the European reference range of 45–60% of energy works out to about 225–300 g of carbohydrates per day.
- Water and electrolytes during training: when plain water is not enough — Plain water is enough for almost everyone, almost all the time.
- Food diary and running: how to tell whether a snack works for you — A light snack before a run can feel uneventful for one person and uncomfortable for another.
This article is for general information. It is not medical advice, a diagnosis, or a prescription for treatment or a diet, and it does not replace a consultation with your doctor. If you have a health condition, are pregnant, take medication, or follow a diet prescribed to you, decisions about food belong with your doctor.
Figures from regulations, guidelines and studies are given as they stood when this article was prepared and may since have changed; check them against the primary sources. This article is not advertising, an offer, or individual advice, and neither the author nor the site owner is responsible for decisions taken on the basis of it.