Nutrition7 min read
How to carb load for a marathon
Carb loading means eating more carbohydrate than usual in the last day or two before a long race, while you train less. It tops up the carbohydrate stored in your muscles, so you can hold your pace for longer before you tire. It does not mean one giant bowl of pasta the night before.
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The short answer
To carb load for a marathon, eat 10–12 g of carbohydrate per kg of bodyweight a day for the 36–48 hours before the start, while you rest or train lightly. For a 70 kg runner, that is 700–840 g a day. Choose lower-fibre, lower-fat foods and spread them across six or more meals and snacks.
- Eat 1–4 g per kg on race morning, 1–4 hours before the start.
- Expect to gain around a kilo: that is water stored with carbohydrate, not fat.
How many carbs should you eat before a marathon?
| Bodyweight | Carbohydrate per day |
|---|---|
| 55 kg | 550–660 g |
| 65 kg | 650–780 g |
| 75 kg | 750–900 g |
| 85 kg | 850–1,020 g |
Work out your own figure with the carb loading calculator, which also gives your race-morning meal.
When should you start carb loading?
Start 36–48 hours before the race. For a Sunday morning marathon, that means Friday morning or Friday lunchtime. Earlier is not better: the joint position statement on athletic nutrition sets 36–48 hours for events longer than 90 minutes, alongside reduced training (Thomas, Erdman and Burke, 2016).
The older seven-day plan with a depletion phase is no longer needed. It adds stress without extra benefit for most runners (Burke et al., 2011).
Best foods for carb loading
- White rice, pasta, noodles, white bread, bagels, crumpets and wraps.
- Potatoes without skins, and breakfast cereals that are not high in fibre.
- Bananas, tinned fruit, fruit juice, jam, honey and maple syrup.
- Sports drinks, milkshakes, rice pudding, sweets and jelly babies to add carbohydrate without bulk.
Cut back on high-fibre foods, beans, large salads and very fatty meals. They fill you up without adding much carbohydrate and can upset your stomach on race day.
A sample carb-loading day for a 70 kg runner
| Meal | Example | Carbohydrate (approx.) |
|---|---|---|
| Breakfast | Large bowl of cornflakes with milk, a banana and a glass of orange juice | 120 g |
| Snack | Two crumpets with jam | 60 g |
| Lunch | Large white bagel with chicken, a sports drink and a pot of rice pudding | 150 g |
| Snack | Two cereal bars and a banana | 80 g |
| Dinner | Large plate of white pasta with tomato sauce, lean meat or tofu, and bread | 200 g |
| Evening | Jelly sweets and a milkshake | 140 g |
What to eat on marathon morning
Eat 1–4 g of carbohydrate per kg of bodyweight 1–4 hours before the start, using the smaller amount if you eat later (Thomas, Erdman and Burke, 2016). White toast with jam, a bagel with honey, or porridge with a banana all work. Use the breakfast you have tested before long runs.
During the race, plan your carbs per hour, gels and fluid with the marathon fuel calculator.
Common carb-loading mistakes
- Eating one huge pasta meal the night before instead of spreading carbohydrate over two days.
- Eating more of everything, including fat and fibre, which adds bulk and calories without enough carbohydrate.
- Trying new foods during race week.
- Worrying about the scales: a gain of around a kilo is stored fuel and water.
Feeling run down after race day? Read what the open window hypothesis says about hard exercise and your immune system.
People also ask
Should I carb load for a half marathon?
Most runners finishing in under 90 minutes do not need a full load. Slower runners can benefit, so use the calculator with your expected time.
Does carb loading make you gain weight?
Yes, usually around a kilo, because your body stores water with carbohydrate. It is fuel, not fat.
Can I carb load with sugar and sweets?
Yes. Low-fibre foods such as juice, sweets and sports drinks are useful for reaching high targets without feeling too full.
Should I still train while carb loading?
Only lightly. Short, easy runs are fine; hard or long sessions use up the stores you are trying to fill.
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Scientific References & Evidence
- Burke, L.M., Hawley, J.A., Wong, S.H.S. and Jeukendrup, A.E. (2011) 'Carbohydrates for training and competition', Journal of Sports Sciences, 29(sup1), pp. S17-S27. doi: 10.1080/02640414.2011.585473. Available at: https://doi.org/10.1080/02640414.2011.585473
- Bussau, V.A., Fairchild, T.J., Rao, A., Steele, P. and Fournier, P.A. (2002) 'Carbohydrate loading in human muscle: an improved 1 day protocol', European Journal of Applied Physiology, 87(3), pp. 290-295. doi: 10.1007/s00421-002-0621-5. Available at: https://doi.org/10.1007/s00421-002-0621-5
- Thomas, D.T., Erdman, K.A. and Burke, L.M. (2016) 'Nutrition and athletic performance', Medicine & Science in Sports & Exercise, 48(3), pp. 543-568. doi: 10.1249/MSS.0000000000000852. Available at: https://doi.org/10.1249/MSS.0000000000000852
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Educational information for adults aged 18 and over. It does not diagnose, treat or manage any medical condition. If you have a health condition, or symptoms that worry you, speak to your doctor or a health professional.