On this page
- What carb loading actually does
- Who needs to carb load?
- How much carbohydrate do you need?
- How to carb load: step by step
- Sample carb-loading menu
- Good and less good foods for carb loading
- The weight gain is normal
- Race morning breakfast
- Fuelling during the race
- A practice run
- Common carb-loading mistakes
- Carb loading for women
- Quick checklist
- FAQ
- Sources
The short version
- Carb loading tops up muscle glycogen. It helps in events longer than about 90 minutes, not in 5 km or 10 km races.
- The current approach is 10 to 12 g of carbohydrate per kg of body weight per day for 36 to 48 hours before the race.
- You don't need the old 'depletion phase'. Reducing training and eating more carbohydrate is enough.
- Expect to gain 1 to 2 kg, mostly water stored with glycogen. That's normal and useful.
- Choose lower-fibre, familiar foods, and practise your loading plan before a long training run.
The pre-race pasta party is one of running's oldest traditions. The night before a marathon, thousands of runners pile their plates high with spaghetti and call it carb loading. Most of them aren't actually loading at all. One big dinner rarely gets close to the amount of carbohydrate that makes a real difference.
Done properly, carb loading is one of the most reliable ways to improve performance in long events. It's also widely misunderstood: when to start, how much to eat, whether you need a depletion phase, and whether it's worth doing for a half marathon or a 10 km.
This guide explains what carb loading does, who benefits, exactly how much to eat and for how long, a sample menu, and the mistakes that leave runners feeling heavy and flat on race morning.
What carb loading actually does
Your muscles store carbohydrate as glycogen. It's the main fuel for moderate to hard exercise. Under normal eating, your stores are enough for roughly 90 minutes of continuous hard effort. After that, glycogen runs low, intensity drops and everything feels much harder. Marathon runners call it hitting the wall.
Carb loading means eating extra carbohydrate while reducing training for a day or two before an event, to fill your muscles with as much glycogen as they can hold. Fuller stores let you hold your race pace longer before fatigue sets in.
A 1997 review by John Hawley and colleagues found that carb loading can delay fatigue in endurance events lasting longer than 90 minutes by around 20%, and improve performance over a set distance by about 2 to 3%. That's a significant gain for the price of some extra rice and bread.
Who needs to carb load?
| Event | Carb load? | What to do instead |
|---|---|---|
| 5 km and 10 km | No | Normal diet plus a carbohydrate-rich meal the night before and a familiar breakfast |
| Half marathon (under ~90 min) | Usually not needed | A higher-carbohydrate day before and a good breakfast |
| Half marathon (over ~90 min) | A light 24-hour load can help | About 7 to 10 g/kg the day before |
| Marathon | Yes | Full 36 to 48 hour load |
| Long triathlons, sportives, ultras | Yes | Full 36 to 48 hour load plus fuelling during |
| Team sports with long matches or tournaments | Sometimes | A higher-carbohydrate day before key matches |
The general rule from Louise Burke and colleagues' 2011 review on carbohydrates for training and competition is that carb loading is useful for events lasting longer than about 90 minutes of continuous exercise. For shorter events, normal glycogen stores are enough.
How much carbohydrate do you need?
The current recommendation is 10 to 12 g of carbohydrate per kilogram of body weight per day for 36 to 48 hours before the event. That's a lot more than most people expect.
| Body weight | 10 g/kg per day | 12 g/kg per day |
|---|---|---|
| 55 kg | 550 g | 660 g |
| 65 kg | 650 g | 780 g |
| 75 kg | 750 g | 900 g |
| 85 kg | 850 g | 1,020 g |
For a 70 kg runner, 10 g/kg means 700 g of carbohydrate a day. To put that in context, a large plate of cooked pasta (about 300 g cooked) contains roughly 90 g. You'd need the equivalent of almost eight of those plates in a day. That's why carb loading means eating carbohydrate at every meal and snack, not just at dinner.
Do you need a depletion phase?
The original carb-loading method, developed in the 1960s, involved a "depletion" phase: several days of hard training and very low carbohydrate intake to empty glycogen stores, followed by several days of high carbohydrate. It worked, but it was miserable and left athletes tired and irritable before races.
In 1981, Michael Sherman and colleagues showed that a simpler approach worked just as well: tapering training while increasing carbohydrate, without the depletion phase. That's the basis of modern carb loading.
Can you load in a day?
Research suggests you can do much of it in about 24 to 36 hours. In 2002, Vanessa Bussau and colleagues found that trained athletes who rested and ate about 10 g/kg of high-glycaemic carbohydrate for a single day almost doubled their muscle glycogen, reaching levels similar to those of longer loading protocols. Most sports dietitians now recommend 36 to 48 hours to be safe and to make the amounts easier to eat.
How to carb load: step by step
- Taper your training. In the final two days before the race, keep running short and easy. Glycogen can't build up if you keep burning it.
- Calculate your target. Body weight in kg × 10 to 12 = grams of carbohydrate per day.
- Spread it out. Eat carbohydrate at every meal and add two or three snacks. Large single meals are uncomfortable.
- Shift the plate. Make carbohydrate the main part of each meal. Reduce fat and protein portions slightly so you're not uncomfortably full.
- Go lower-fibre. Swap some wholegrain foods for white rice, white bread, pasta, potatoes without skins, and juice. Lower fibre means less bulk and fewer stomach problems on race day.
- Drink carbohydrate. Juice, sports drinks and milk-based drinks add carbohydrate without filling you up as much as solid food.
- Keep it familiar. This isn't the time to try new foods or restaurants.
Most people underestimate how much they need to eat. For your first carb load, use food labels or a nutrition app to check you're actually hitting your target. After a couple of races you'll know what it looks like.
Sample carb-loading menu
Here's an example day for a 70 kg runner aiming for around 700 g of carbohydrate. Quantities are approximate.
| Meal | Food | Carbs (approx.) |
|---|---|---|
| Breakfast | Large bowl of cornflakes or rice cereal with milk, 2 slices of white toast with jam, glass of orange juice | ~150 g |
| Mid-morning | Bagel with honey, banana | ~85 g |
| Lunch | Large white rice dish with chicken or tofu and a little sauce, a glass of juice | ~150 g |
| Afternoon | Rice cakes with jam, a sports drink (500 ml), a handful of jelly sweets | ~100 g |
| Dinner | Large plate of pasta with tomato sauce, white bread roll | ~150 g |
| Evening | Rice pudding or a milk-based drink with a cereal bar | ~65 g |
| Total | ~700 g |
Notice how much of it comes from simple, lower-fibre foods and drinks. Trying to hit 700 g with lentils, wholemeal pasta and vegetables would be uncomfortable and likely cause stomach trouble on race day.
Good and less good foods for carb loading
| Good choices | Go easy on |
|---|---|
| White rice, pasta, noodles | High-fibre wholegrains, bran |
| White bread, bagels, wraps | Beans and lentils in large amounts |
| Potatoes without skin | Large salads and raw vegetables |
| Breakfast cereals (lower fibre) | Fatty or fried foods |
| Bananas, tinned fruit, dried fruit in moderation | Rich creamy sauces |
| Juice, sports drinks, flavoured milk | Spicy foods you don't usually eat |
| Honey, jam, rice cakes, jelly sweets | Alcohol |
The weight gain is normal
Each gram of glycogen is stored with roughly three grams of water. A full carb load often adds 1 to 2 kg to your body weight. Some runners panic about this. Don't. It's a sign your muscles are full of fuel and extra water, both of which you'll use during the race.
You might feel slightly heavy or sluggish on the morning of the race. Most runners find that feeling disappears within the first few kilometres.
Race morning breakfast
Carb loading fills your muscle glycogen. Overnight, your liver glycogen drops, so breakfast still matters. The guidelines suggest 1 to 4 g of carbohydrate per kg in the one to four hours before the start.
Good race-morning options:
- White toast or bagel with honey or jam, and a banana.
- Porridge made with milk, plus honey.
- Rice cakes with jam and a sports drink.
- Whatever you've practised before long training runs.
Eat about 3 hours before the start if you can. Small top-ups, such as a sports drink or a gel, can come closer to the start. Our guide to eating before, during and after exercise covers this in more detail.
Fuelling during the race
Carb loading doesn't replace fuelling during the race. In a marathon, it simply means you start with full stores. The guidance from Asker Jeukendrup's research is to take in about 30 to 60 g of carbohydrate an hour for events of 1 to 2.5 hours, and up to 90 g an hour for longer events, ideally from sources that mix glucose and fructose.
Practise your race fuelling in long training runs. Your gut can be trained to tolerate more carbohydrate with regular practice.
A practice run
Don't try carb loading for the first time before your goal race. About three to four weeks before, practise before your longest training run:
- Load for 36 to 48 hours using the foods you plan to eat before the race.
- Eat your planned race breakfast.
- Use your planned race fuelling during the run.
- Note how your stomach felt, how your energy held up and how heavy you felt.
- Adjust for race week.
Common carb-loading mistakes
- Only loading at dinner. One big pasta meal isn't enough. Spread it across the day or two.
- Eating far too much fat and protein. Huge portions of everything leave you uncomfortable without filling glycogen stores.
- Too much fibre. Wholegrains, beans and salads in large amounts can cause stomach problems on race day.
- Training hard during the load. Keep the last two days easy.
- Trying new foods. Stick to what you know.
- Skipping breakfast on race day. Liver glycogen needs topping up.
- Panicking about weight gain. It's mostly water and glycogen.
- Drinking alcohol. It doesn't help glycogen storage and can affect sleep.
Carb loading for women
The per-kg recommendations are the same for women. Some older studies found women stored less glycogen when loading, but that seems to be largely because they increased the proportion of carbohydrate without increasing total food intake. When women eat enough total energy as well as enough carbohydrate, they can load effectively.
Quick checklist
- Is your event longer than about 90 minutes? If not, skip the full load.
- Calculate 10 to 12 g/kg of carbohydrate per day.
- Start 36 to 48 hours before the race.
- Taper training to short, easy sessions.
- Eat carbohydrate at every meal and snack, mostly lower-fibre options.
- Drink some of your carbohydrate.
- Expect 1 to 2 kg of weight gain.
- Eat a familiar carbohydrate breakfast about 3 hours before the start.
- Fuel during the race with 30 to 90 g of carbohydrate an hour.
Carb loading won't make up for missing training, but it ensures you can use all the fitness you've built. If you're preparing for a longer race, our Zone 2 training guide explains how to build the aerobic base that long events depend on.
Frequently asked questions
Do I need to carb load for a half marathon?
For most runners finishing in under about 90 minutes, normal eating plus a good pre-race meal is enough. Slower half marathoners may benefit from a lighter 24-hour load.
Should I carb load for a 10 km race?
No. Your normal glycogen stores are more than enough for races under about an hour. A carbohydrate-rich dinner the night before and a familiar breakfast are all you need.
Is a big pasta dinner the night before enough?
Usually not on its own. One large meal rarely gets close to 10 to 12 g/kg. Spread carbohydrate across the day or two before instead.
Will carb loading make me feel heavy?
You'll gain some water weight, which can feel slightly sluggish at first. It's a sign glycogen stores are full, and most runners feel good once they start racing.
Can I carb load on a low-fibre diet?
Yes, and it's recommended. Swapping some wholegrains for white rice, white bread, pasta and juice makes the volume easier and reduces stomach problems.
Do women need to carb load differently?
The same per-kg targets apply. Some research suggests women may need to make sure total energy intake rises too, not just the share of carbohydrate.
Sources and further reading
- Burke LM, et al. Carbohydrates for training and competition. Journal of Sports Sciences, 2011;29(Suppl 1):S17-S27. DOI PubMed
- Bussau VA, et al. Carbohydrate loading in human muscle: an improved 1 day protocol. European Journal of Applied Physiology, 2002;87(3):290-5. DOI PubMed
- Sherman WM, et al. Effect of exercise-diet manipulation on muscle glycogen and its subsequent utilization during performance. International Journal of Sports Medicine, 1981;2(2):114-8. DOI PubMed
- Hawley JA, et al. Carbohydrate-loading and exercise performance. An update. Sports Medicine, 1997;24(2):73-81. DOI PubMed
- Thomas DT, et al. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 2016;116(3):501-528. DOI PubMed
- Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 2014;44 Suppl 1(Suppl 1):S25-33. DOI PubMed
This guide is general education, not a diagnosis or treatment plan. If you have pain that is severe, getting worse or not improving after two to three weeks, see a doctor or physiotherapist. Read our full medical disclaimer.
Photography: Unsplash contributors. Published 14 October 2026, last reviewed 14 October 2026.
