Marathon Carb Loading: A Race-Week Plan (Grams per Kg + Foods)

Marathon carb loading means eating 8-12 grams of carbohydrate per kilogram of body weight per day for the 2-3 days before your race while you taper training, so your muscles store the maximum amount of glycogen. That extra fuel is what delays the deep fatigue runners call “the wall” in the final miles. Done right, it is not a single giant pasta dinner but a short, deliberate shift in what and how much you eat during race week. This is general nutrition guidance, not medical advice; if you have diabetes, digestive conditions, or other health concerns, talk with a clinician or sports dietitian before changing your diet.

Why Carb Loading Works

Your body stores carbohydrate as glycogen in muscles and the liver, and that glycogen is the fastest fuel you burn while running at marathon effort. A typical runner stores enough for roughly 90-120 minutes of hard running. Since most marathoners are out there for three, four, or five hours, an unloaded runner can run the tank low well before the finish, which is when pace collapses and form falls apart.

Carb loading supersaturates those glycogen stores above their normal level. Combined with the reduced mileage of a taper, it lets you start the race with a fuller tank so you burn through it more slowly. It does not replace fueling during the race, but it raises the ceiling you start from. This is the nutritional half of a strong finish; the training half is covered in our marathon training plan for beginners and the broader running training plan guide.

How Many Carbs: The Grams-per-Kilogram Formula

Skip vague advice like “eat lots of pasta.” Use body weight math. The research-supported target is 8-12 g of carbohydrate per kg of body weight per day, with most runners doing well near 8-10 g/kg.

Body weight	8 g/kg (daily)	10 g/kg (daily)
55 kg (121 lb)	440 g	550 g
70 kg (154 lb)	560 g	700 g
85 kg (187 lb)	680 g	850 g

To picture 560 grams: that is roughly 4 cups of cooked rice, 3 bananas, 2 bagels, a sports drink, and a large plate of pasta spread across the day. It is a lot of food, which is why you spread it over several meals and snacks rather than one blowout dinner. Track it loosely for your first loading cycle so you learn what your number actually looks like on a plate.

The 2-3 Day Race-Week Protocol

Modern loading is short. The old seven-day “deplete then load” method left runners flat and irritable, and research shows trained runners fully top off glycogen in 24-48 hours. For a Sunday race:

• Thursday: Normal balanced eating. Start hydrating well. Training is light as your taper winds down.
• Friday (2 days out): Shift toward carbs, aiming for the low end of your g/kg target. Begin trimming fiber and fat.
• Saturday (1 day out): Your biggest loading day at 8-10 g/kg. Eat carb-rich meals and snacks every few hours. Keep the evening meal moderate in size so you sleep well.
• Sunday (race day): A tested carb breakfast 3-4 hours before the start, then a small top-up near the gun.

The key move is that carbs replace fat and fiber calories rather than adding to them. You are not eating more total food so much as changing the ratio. Because you are barely running, those carbs go into storage instead of getting burned. If your race is shorter, the same logic scales down; a lighter version suits a half marathon, while sharpening sessions like tempo runs should already be done by loading week.

What Foods to Eat

Favor low-fiber, familiar, easy-to-digest carbohydrates. Good staples include:

• White rice, pasta, and noodles
• White bread, bagels, English muffins, and pancakes
• Potatoes (peeled) and sweet potatoes in moderation
• Oatmeal, cream of wheat, and low-fiber cereals
• Bananas, applesauce, and canned peaches
• Pretzels, crackers, rice cakes, and plain cookies
• Sports drinks, juice, and honey for easy liquid carbs

Add a modest amount of lean protein at meals (eggs, chicken, fish, tofu) to feel satisfied, but keep portions small so carbs stay the focus. Liquid carbs like juice and sports drinks are useful when you simply cannot chew any more rice. What you eat before your daily easy runs during this week follows the same low-residue logic covered in our guide on what to eat before a run.

What to Avoid During Loading Week

The fastest way to ruin a good loading plan is a race-morning bathroom emergency. To lower that risk:

• Cut high-fiber foods the day or two before: large salads, beans, bran, whole grains, and raw cruciferous vegetables. Fiber is healthy day to day but it sits in your gut and causes cramps and urgency mid-race.
• Go easy on fat. Heavy, greasy, or creamy meals digest slowly and crowd out carbs. Skip the deep-fried appetizer and the rich alfredo.
• Never try new foods. Race week is not the time for an exotic restaurant or an untested gel. Rehearse your loading foods and pre-race breakfast during long-run training so nothing surprises your stomach.
• Do not overdo alcohol. It dehydrates you and disrupts sleep the night before.
• Do not skip salt. Sodium helps you hold onto the water that comes with glycogen storage, which supports hydration.

Race-Morning Breakfast

Eat a carb-rich, low-fiber, low-fat breakfast 3-4 hours before the start, targeting roughly 1-4 g of carb per kg of body weight. Proven options include a bagel with honey or jam, oatmeal with a sliced banana, toast with peanut butter scraped thin, or pancakes with syrup. Sip water or a sports drink alongside it.

Then 30-60 minutes before the gun, top up with something small and quick: a banana, a gel, a few sips of sports drink, or a handful of pretzels. This tops off liver glycogen, which dips overnight while you sleep. Every part of this breakfast should be something you have eaten before a long training run, not a first attempt. Loading fuels the start; smart pacing protects the finish, and our guides to running faster and holding proper running form help you spend that stored energy efficiently once the race begins.

Putting It Together

Carb loading is simple once you make it concrete: for two or three days you eat 8-10 g of carbohydrate per kg of body weight, lean on familiar low-fiber foods, cut fat and fiber, hydrate with a little extra salt, and cap it with a rehearsed race-morning breakfast. Practice the whole sequence before a long training run at least once so race week feels routine rather than experimental. Combine a full tank with the fitness you built across your training block and the final miles will feel far more manageable than they do on empty. When in doubt about your individual needs, a registered sports dietitian can tailor these numbers to you.