The short answer
Marathon carbohydrate loading is not a giant pasta dinner. It is a planned rise in carbohydrate availability across the final day or two while training volume falls, using foods and portions the athlete already tolerates.
For events lasting more than about 90 minutes, commonly used sports-nutrition guidance describes 10–12 g of carbohydrate per kg of body mass per day for the final 36–48 hours, alongside reduced training.1, 2 This is a high intake to plan and rehearse, not a number to force despite symptoms. The three-day worksheet uses the first day for preparation and the final two for the loading plan.
First decide whether this needs professional help
Do not use an internet grams-per-kilogram target as a self-prescription if you have diabetes, kidney disease, gastrointestinal disease, a history of disordered eating, significant food allergies, or a clinician-directed diet. A sports dietitian can turn the evidence into a safe plan.
For other athletes, start with a food audit rather than a number:
- Which carbohydrate-rich foods have worked before long runs?
- Which high-fibre, high-fat, or unfamiliar foods create symptoms?
- What can you obtain at the race location?
- How early is the start?
- Will nerves reduce appetite?
The three-day worksheet
Three days before: remove novelty
Your job is to make the plan executable.
- Confirm breakfast and snack access.
- Buy or pack the exact race fuel.
- Keep normal meals and adequate carbohydrate.
- Avoid a sudden restriction intended to "earn" race-week food.
- Note any travel or time-zone disruption.
This is also the last reasonable point to change logistics. It is not the time to test a new supplement.
Two days before: shift the plate
Increase familiar carbohydrate foods while keeping the meal comfortable.
| Keep | Increase if tolerated | Reduce only if it normally causes trouble |
|---|---|---|
| Familiar protein portions | Rice, bread, potatoes, oats, cereal, fruit, tolerated sports foods | Very large fibre loads, heavy fried meals, unfamiliar sauces |
The aim is not to eliminate protein, vegetables, or pleasure. It is to avoid letting very bulky or fatty choices crowd out the carbohydrate you intend to eat.
One day before: make intake easy
Spread food across meals and snacks rather than forcing one enormous dinner. Use lower-bulk familiar options if appetite is limited. Finish the day knowing what breakfast is, when it will happen, and what will travel to the start.
If body mass rises slightly, that can reflect stored glycogen, associated water, and food volume—not sudden loss of fitness. Do not respond with restriction or a last-minute sweat session.
Calculate the amount, then check whether the plan is practical
daily carbohydrate grams = body mass in kg × chosen grams per kg
The table shows the arithmetic of the published 10–12 g/kg/day range. It is not an individual prescription or a promise of faster racing.
| Body mass | At 10 g/kg/day | At 12 g/kg/day |
|---|---|---|
| 50 kg | 500 g carbohydrate | 600 g carbohydrate |
| 60 kg | 600 g carbohydrate | 720 g carbohydrate |
| 70 kg | 700 g carbohydrate | 840 g carbohydrate |
| 80 kg | 800 g carbohydrate | 960 g carbohydrate |
Grams of carbohydrate are not grams of food. A 100 g portion of rice is not automatically 100 g carbohydrate. Use the label or a reliable food-composition record for the exact product and serving, paying attention to cooked versus dry weight.
A worked 600 g planning example
For a hypothetical 60 kg runner using 10 g/kg/day, the calculation is 60 × 10 = 600 g/day. One way to distribute that total is:
| Eating occasion | Illustrative carbohydrate allocation | Foods to consider if already tolerated |
|---|---|---|
| Breakfast | 120 g | Cereal or oats, bread, fruit |
| Mid-morning | 60 g | Bread, juice, or a familiar snack |
| Lunch | 140 g | Rice, pasta, or potatoes with familiar accompaniments |
| Afternoon | 80 g | Bagel, cereal, fruit, or tolerated sports food |
| Dinner | 140 g | Another familiar carbohydrate-based meal |
| Evening | 60 g | A comfortable snack |
| Total | 600 g | Confirm actual portions from labels |
The food names are options, not quantified serving equivalents. Build actual portions from what you eat and tolerate, keep ordinary protein and overall nutrition in view, and ask a sports dietitian for help if the amount is difficult to achieve comfortably.3 Do not copy the total if the body mass, target, or medical context does not fit you.
If the plan creates severe fullness, pain, or diarrhoea, do not keep forcing food to complete a spreadsheet. Spread intake, revisit food choices with appropriate support, and use what you have rehearsed. There is no single menu that every runner must follow.
Race-morning handoff
Carbohydrate loading does not replace breakfast or the during-race strategy. Write a single handoff card:
- wake time;
- breakfast time;
- familiar breakfast;
- small pre-start top-up if already tested;
- first on-course fuel cue;
- fluid opportunity;
- backup product.
Then connect it to the 30-60-90 practice framework. The jobs are different: loading prepares stored fuel; race fueling helps maintain availability during the event.
Common errors
- saving the entire increase for dinner;
- copying an elite athlete's menu or supplement stack;
- interpreting "low fibre" as "no plants for a week";
- drinking excessive plain water because glycogen stores water;
- trying a high-caffeine product for the first time;
- restricting after seeing scale weight rise;
- assuming loading can compensate for an over-aggressive pace.
A loading strategy cannot repair inadequate training or an over-aggressive pace. Evidence about muscle glycogen storage is also not identical to evidence that an individual runner will finish faster.
Run a smaller rehearsal before race week
Use a key long-run weekend to test the logistics, not to duplicate every race-week gram. Practise the same breakfast timing, one day of the higher-carbohydrate food pattern, and the planned on-run products. Record appetite, bowel symptoms, sleep, energy, and whether the plan was practical around work or travel.
What the evidence supports—and what remains uncertain
A 2026 systematic review included 63 trials in its descriptive synthesis and found substantial variation in glycogen responses.4 It supports the importance of carbohydrate availability, but it does not make the upper end of a range a compulsory target for every athlete.
A separate 2026 commentary highlights limited blinding and inconsistent in-race fueling in carbohydrate-loading studies.5 That matters because a change in stored glycogen and a race-performance benefit are different outcomes. Treat the standard range as an evidence-informed planning framework, not a guaranteed number of minutes saved.
Gastrointestinal nutrition research also does not justify a blanket gluten-free or restrictive diet for all endurance athletes.6 If a particular food pattern causes repeated symptoms, investigate it rather than removing whole food groups indefinitely.
Hydration is a separate decision
Do not force large amounts of plain water because you are increasing carbohydrate intake. Individual fluid needs vary with conditions and the athlete.7 Excess drinking can be dangerous; exercise-associated hyponatremia guidance specifically addresses that risk.8 A loading calculation does not determine how many litres you need.
Use the sweat-rate worksheet for rehearsals in comparable conditions, and the gel-count worksheet to separate pre-race meals from carbohydrate consumed during the marathon.
Common questions
Should I carb load for all three days?
The three-day structure reserves day three before the race for shopping, meal planning, and normal adequate eating. The commonly cited loading window is the final 36–48 hours.1, 2 Do not add an exhausting depletion workout to make loading feel necessary.
What if I gain weight before the race?
Stored glycogen, associated water, and food volume can affect scale weight. Do not react with restriction or extra exercise. The point of this plan is preparing fuel availability, not achieving a particular race-morning weight.
Can one pasta dinner do the job?
It is easier to plan across meals and snacks than to force the intended increase into one dinner. The meal-distribution example above shows the size of the task; actual portions depend on the products and your tolerance.
Safety boundary
This is educational and not medical advice or individual nutrition advice. Recurrent gastrointestinal symptoms, restrictive eating, menstrual disruption, persistent fatigue, major unplanned weight change, or concern about low energy availability needs qualified assessment. Seek urgent care for confusion, collapse, chest pain, severe breathing difficulty, or persistent vomiting.
26weeks.ai keeps the training and race-week decisions connected without selling a magic meal. Start training now.
References
Sources and associated claims reviewed October 17, 2026. Practical examples are editorial guidance, not independently validated protocols.
1 Human Performance Resources by CHAMP. Carb loading the right way. Read the source.
2 Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers. (2019). Read the source.
3 American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. (2016). Read the source.
4 Dietary Carbohydrate Intake and Skeletal Muscle Glycogen: A Systematic Review and Meta-Analysis to Determine Optimal Carbohydrate Loading Strategies. (2026). Read the source.
5 Beyond Belief? Absence of Double-Blinding and Limited Ecological Validity in Carbohydrate Loading Research. (2026). Read the source.
6 Use of Carbohydrate (CHO), Gluten-Free, and FODMAP-Free Diets to Prevent Gastrointestinal Symptoms in Endurance Athletes: A Systematic Review. (2024). Read the source.
7 American College of Sports Medicine position stand. Exercise and fluid replacement. (2007). Read the source.
8 Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. (2015). Read the source.