How to use
- 1Enter your body weight in kg or lb.
- 2Choose the race duration: under 60 minutes, 60–90 minutes or over 90 minutes.
- 3For long races set the number of loading days and the g/kg target.
- 4Read daily and per-meal grams, race-morning and in-race targets and the food table.
Current guidelines (ACSM 2016)
The 2016 joint position statement of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada recommends 10–12 g of carbohydrate per kg of body weight per day for 36–48 hours before events longer than 90 minutes. For 60–90 minute events 7–12 g/kg over the final 24 hours is enough, and shorter races need no special loading. A meal with 1–4 g/kg 1–4 hours before the start is advised, and during exercise 30–60 g per hour for 1–2.5 hours, up to 90 g per hour for longer efforts.
What to eat in practice
Example: a 70 kg (154 lb) marathoner at 10 g/kg needs 700 g of carbs a day, or 1,400 g over two days. That is about 175 g at each main meal plus two snacks of about 88 g; 175 g is roughly three bowls of cooked rice or almost three plates of pasta. Because the volume is large, dense sources such as honey, jam, juice, bagels and sports drinks help. Cut back on fibre, beans and fat, and do not try new foods in race week.
Things to know
Glycogen is stored with water, so a temporary gain of 1–2 kg (2–4 lb) is normal. Rather than adding calories, swap some fat and protein for carbs. If you have diabetes, digestive problems or follow a special diet, talk to your doctor or a sports dietitian first. This tool is not medical advice.
Frequently asked questions
How many carbs should I eat before a marathon?
10–12 g per kg per day over the last 36–48 hours, which is 700–840 g a day for a 70 kg runner.
Do I need to carb load for a half marathon?
If you finish in under 90 minutes, classic loading is not needed; 7–8 g/kg the day before and a good race breakfast are enough.
What should I eat on race morning?
1–4 g/kg of carbohydrate 1–4 hours before the start, such as a bagel with honey, a banana or porridge, low in fibre and fat.
Does carb loading make you gain weight?
Yes, 1–2 kg of water stored with glycogen. It is not fat, and it becomes fuel and fluid during the race.
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