How do you carb load for a marathon?
To carb load for a marathon, eat about 8 to 12 g of carbohydrate per kg of body weight a day for the last 24 to 48 hours, and cut fibre and fat to make room. For a 70 kg runner that is roughly 560 to 840 g a day. Rice, pasta, pap, bread, potatoes and juice do the job without special products.
- Carb loading: about 10 to 12 g/kg/day for 36 to 48 hours before events over 90 minutes (ACSM, AND and Dietitians of Canada, 2016).
- A 70 kg runner needs roughly 560 to 840 g of carbohydrate a day at 8 to 12 g/kg.
- Expect 1 to 2 kg weight gain from glycogen and water; it is not fat.
- Biogen Carbogen Low GI works out at about R15.60 to R21.67 per 50 g serving at Dis-Chem (October 2026).
What does the evidence say?
Carbohydrate loading increases muscle glycogen and delays fatigue in events lasting longer than about 90 minutes. The 2016 joint position stand (ACSM, Academy of Nutrition and Dietetics, Dietitians of Canada) cites about 10 to 12 g/kg/day for 36 to 48 hours before events over 90 minutes; many coaches use 8 to 10 g/kg for 24 to 36 hours for a marathon. Evidence level: strong, with real individual differences in benefit. It is separate from carbohydrate taken during the race (see how many carbs per hour).
How much is that in grams?
| Body weight | 8 g/kg | 10 g/kg | 12 g/kg |
|---|---|---|---|
| 55 kg | 440 g | 550 g | 660 g |
| 70 kg | 560 g | 700 g | 840 g |
| 85 kg | 680 g | 850 g | 1 020 g |
These are large numbers. You will not manage them by adding pasta to your usual meals.
What should you eat?
Approximate carbohydrate in familiar South African foods (check labels):
- Cooked white rice or pasta, 1 cup (about 200 g): roughly 55 g
- Stiff maize-meal pap, a generous serving: roughly 40 to 60 g
- A slice of white bread: roughly 15 g; with jam or honey a few extra grams
- Medium banana: roughly 25 g
- 250 ml fruit juice: roughly 25 g
Aim for four to six carb-based meals and snacks a day, and use liquid carbohydrate (juice, cordial, a carb drink) to reach the total without feeling stuffed. A carbo-loader such as Biogen Carbogen Low GI (900 g, 18 servings of 50 g) cost R280.79 to R389.99 at Dis-Chem in October 2026, about R15.60 to R21.67 per serving; carbohydrate per serving is not published in the text we checked. 32Gi Race drink gives 68 g per 75 g serving at about R39 a serving. Food is cheaper; powders just add convenience.
What should you cut back?
Reduce fibre, large salads, and fatty or very spicy foods for the final 24 hours to limit stomach upset on race morning. Keep protein modest rather than dropping it entirely.
Common mistakes
- Loading on race eve only. The big meal the night before helps less than two days of steady eating.
- Trying new foods. Practise your loading menu before a long training run.
- Expecting to feel light. Glycogen holds water, so 1 to 2 kg of weight gain is normal and not fat.
- Under-drinking. Keep fluids up, and see how to avoid hitting the wall for race-day fuel.
Who should not follow this?
People with diabetes need an individual plan with their doctor or dietitian. Anyone with coeliac disease, reflux or irritable bowel should adjust the food choices with a dietitian. For races under 90 minutes loading is rarely needed; just eat normally with a carbohydrate-rich dinner.
Compare drinks on our carb drinks for cycling guide.
Teenage runners should carb load with normal meals rather than powders, and pregnant runners, people with kidney disease and anyone on regular medication should check with a doctor or dietitian.
Products mentioned, with dated prices
| Product | Size | Price | Servings | R per serving | Sweeteners |
|---|---|---|---|---|---|
| Biogen Carbogen Low GI carbo-loader (900 g) | 900 g | R281–R390Dis-Chem Living Fit, Oct 2026 | 18 | R21.67 | Not published |
| 32Gi Race High Intensity Sports Drink (900 g) | 900 g | R470Dis-Chem Living Fit, Oct 2026 | 12 | R39.17 | None listed |
| Biogen Cytogen Race Mix (800 g) | 800 g | R277–R385Dis-Chem Living Fit, Oct 2026 | 16 | R23.44 | Not published |
Compare the options
Related questions
- How many carbs per hour do you need for a marathon or ultra?
- How do you avoid hitting the wall in a marathon?
- What should you eat, drink and take during the Comrades Marathon?
- What should you take for the Two Oceans Marathon?
- What is the best carb drink for cycling in South Africa?
Sources
- Thomas, Erdman & Burke 2016, Position of the Academy of Nutrition and Dietetics, Dietitians of Canada and ACSM: Nutrition and Athletic Performance
- Jeukendrup 2014, A step towards personalized sports nutrition: carbohydrate intake during exercise (Sports Med)
- Australian Institute of Sport Supplement Framework, Group A
Educational information only, not medical advice. Speak to a doctor, pharmacist or registered dietitian before using supplements if you are pregnant or breastfeeding, under 18, taking medication, or living with kidney, liver or heart disease.
Cite this page: Healthnews24, “How do you carb load for a marathon?”, updated 27 October 2026, https://www.healthnews24.co.za/answers/carb-loading-for-a-marathon-how-to/. Plain-text version: /answers/carb-loading-for-a-marathon-how-to.md