Carbohydrate loading before a race: marathon and half marathon week
Who needs to load, what 10–12 g/kg a day for 36–48 hours looks like on the plate, and what to eat on race morning and during the race. A day-by-day plan for a 70 kg runner.
In marathon week, runners' minds usually swing to one of two extremes: either they eat a giant plate of pasta on Saturday night and consider the job done, or they cut out bread completely to avoid gaining weight. Both get billed at the 30th kilometre. Carbohydrate loading isn't a single dinner. It is a planned process spread over 36–48 hours, with a week of preparation before it. Below I explain who actually needs to load, how to build the plate gram by gram for a 70 kg runner, and what to do on race morning and during the race.
Why does glycogen matter so much?
Muscles and the liver store carbohydrate as glycogen. During long, steady-to-hard running, that store is the muscle's preferred fuel. As it runs down, holding the same pace gets harder; what runners call "hitting the wall" is usually exactly this. Training makes the store bigger, but whether you start the race with it full depends on what you eat in the last two days. Loading aims to push the store to a level you can't reach with normal daily eating.
Who needs to load?
The 2016 joint position statement of the ACSM, the Academy of Nutrition and Dietetics and Dietitians of Canada draws a clear line:
- Races shorter than 90 minutes (10K, a fast half marathon): 7–12 g/kg of carbohydrate over the 24 hours before the race, a "general fuelling up", is enough.
- Continuous or intermittent races lasting more than 90 minutes (marathon, a half marathon taking longer than 90 minutes, long cycling and triathlon events): loading with 10–12 g/kg per day for 36–48 hours before the race is recommended.
A runner finishing a half marathon in 1:25 and one finishing in 2:10 may be in the same race, but their fuel needs are different. Start by looking at your own finishing time.
The baseline on training days
Loading only makes sense if you eat enough carbohydrate through the rest of the week too. The same statement gives these daily ranges by training load:
| Training load | Example | Daily carbohydrate |
|---|---|---|
| Light | Low-intensity or skill-based work | 3–5 g/kg |
| Moderate | About 1 hour a day at moderate intensity | 5–7 g/kg |
| High | 1–3 hours a day at moderate-to-high intensity | 6–10 g/kg |
| Very high | More than 4–5 hours a day at moderate-to-high intensity | 8–12 g/kg |
Marathon week: a day-by-day plan
Let's work with a 70 kg runner racing a marathon on Sunday morning. Training volume is already dropping this week, so they burn less fuel, yet by the end of the week we want to store more of it.
- Monday to Wednesday: Normal eating pattern, 5–7 g/kg depending on training load (350–490 g). No new foods. Test your race-morning breakfast before a long run on one of these days.
- Thursday: Easy run. Moderate carbohydrate, normal portions of vegetables and pulses.
- Friday and Saturday (loading): 10–12 g/kg a day, which is 700–840 g of carbohydrate. We cut back on fibre and fat and increase the number of meals.
- Sunday morning: A tested breakfast about 3 hours before the start.
What does 700 grams of carbohydrate look like on a plate?
For someone who isn't used to it, this really is a lot. Three big meals won't get you there; you need to split it across six meals and take some of it as fluid. The values below are approximate:
| Meal | Contents | Approx. carbohydrate |
|---|---|---|
| Breakfast | 3 slices white bread, 2 tablespoons grape molasses (pekmez), 1 banana, 1 glass fruit juice, a little white cheese | 125 g |
| Snack | 1 simit, 1 ayran | 60 g |
| Lunch | 200 g (dry weight) pasta with tomato sauce, grilled chicken; 1 slice bread | 160 g |
| Snack | 60 g dates, 500 ml sports drink or diluted fruit juice | 75 g |
| Dinner | 180 g (dry weight) rice pilaf, boiled potato, 2 slices bread, lean oven-baked sea bass | 200 g |
| Late evening | 1 bowl sütlaç (rice pudding) | 45 g |
| Through the day | An extra 500 ml fruit juice | 50 g |
| Total | ~715 g (≈10 g/kg) |
I deliberately chose rice over bulgur and white bread over wholemeal here. Bulgur and whole grains are valuable on normal days, but on these two days extra fibre in the gut means gas and bloating on race morning. Dried apricots are fibrous too, so I keep that portion small during loading. Rich sauces, fried food and creamy dishes fill you up without leaving room for carbohydrate and also slow digestion.
A higher number on the scale is normal
Glycogen is stored in muscle together with water. Seeing the scale go up a little after loading is a sign that the stores have filled, not that you have gained fat. That slightly heavy feeling in the legs comes from the same thing and disappears in the first kilometres of the race.
Race morning
The statement recommends 1–4 g/kg of carbohydrate 1–4 hours before the race. The shorter the gap, the smaller the amount. About 3 hours out, our 70 kg runner can aim for 2 g/kg, which is around 140 g:
- 3 slices white bread with a thin layer of honey or jam
- 1 banana
- 1 glass of fruit juice
- Tea or coffee if you're used to it
Don't try anything new. The menemen, sucuk or börek you see for the first time at a hotel breakfast have no place on race morning. If you are racing in another city, take your own bread and bananas with you.
During the race
The statement's in-race guidance changes with duration:
- Under 45 minutes: No extra carbohydrate needed.
- 45–75 minutes: Small amounts, or a mouth rinse with a carbohydrate drink, may be enough.
- 1–2.5 hours: 30–60 g per hour.
- Longer than 2.5 hours: up to 90 g per hour, using blends such as glucose and fructose that are absorbed through different transporters.
Most gels contain 20–30 g of carbohydrate per sachet; read the label. For 60 g an hour, roughly two gels, or one gel plus sports drink, will do. Getting up to 90 g is something your gut has to adapt to. We practise it on long runs for weeks beforehand, not on race day. Taking a gel with water from the aid station matters for stomach comfort.
Half marathon week
If you'll run the half marathon in under 90 minutes, you don't need a full load. Raising carbohydrate to the 7–12 g/kg range over the last 24 hours, without overdoing it, is enough; for 70 kg that is 490–840 g, and for most runners the lower and middle values are a comfortable target. If you'll be out longer than 90 minutes, you can consider a shorter version of the marathon plan, loading over the final 36 hours. During the race, the 30–60 g per hour guidance for 1–2.5 hours applies.
Common mistakes
- Squeezing the whole load into the dinner the night before.
- Raising fat and protein at the same rate as carbohydrate and getting uncomfortably full.
- Stressing the gut with lots of pulses, salad and bran products on loading days.
- Using gels for the first time on race day.
- Forgetting fluid; storing glycogen needs water too.
Frequently asked questions
Should I keep eating protein while loading?
Yes, though portions can be a bit smaller than usual. Keep a reasonable amount of protein at each meal from lean sources such as chicken, fish and yoghurt, and give most of the plate to carbohydrate.
I eat gluten-free. What can I use?
Rice, potatoes, corn, gluten-free pasta, fruit, dates, honey, grape molasses and fruit juice will get you to the same target. If you have coeliac disease, research safe options in the race city well in advance.
I have a sensitive stomach. Is loading right for me?
Cutting fibre and fat, eating smaller but more frequent meals and taking some of the carbohydrate as fluid eases the problem for most athletes. If you have a diagnosed digestive condition, build the plan with your doctor and dietitian.
Should female runners aim for the same amounts?
The per-kilogram ranges are the same. On loading days, though, total energy intake also has to be adequate; if you raise carbohydrate but shrink your overall meals, the stores may not reach the expected level.
