Carb loading means eating a high-carbohydrate diet in the days before a long endurance event to maximize the fuel stored in your muscles. The target is 10 to 12 grams of carbohydrates per kilogram of body weight per day, starting 36 to 48 hours before race day. For a 150-pound (68 kg) athlete, that works out to roughly 680 to 816 grams of carbs daily, which is a lot more food than most people expect. The strategy only provides a measurable performance benefit for events lasting longer than 90 minutes, like marathons, long-distance cycling, or triathlons.
How Much to Eat and When to Start
General sports nutrition guidelines recommend 6 to 10 grams of carbs per kilogram of body weight for everyday training needs. Carb loading pushes that to 10 to 12 g/kg for the 36 to 48 hours before competition. Many elite endurance athletes begin shifting their diet about 10 days out, gradually increasing carbs while tapering training volume so the body has time to pack glycogen into muscle tissue without the constant drain of hard workouts.
Your muscles can store between 350 and 700 grams of glycogen depending on your training status, body size, and muscle fiber composition. Your liver holds another 100 grams or so. Every gram of stored glycogen pulls about 3 grams of water along with it. That means a fully loaded athlete might carry an extra 1,500 to 1,800 grams of water just from glycogen storage alone. Gaining 2 to 4 pounds during a carb load is normal and expected. That water weight actually helps with hydration during the race, since it gets released as your muscles burn through their fuel.
The Best Foods for Carb Loading
The key principle is choosing carbs that are easy to digest and low in fiber. This is one of the rare times when refined grains are the better choice. White rice, white bread, plain pasta, bagels, and pancakes are all staples of a carb-loading diet because they deliver dense carbohydrates without the bulk that slows digestion. High-fiber foods like brown rice, whole wheat bread, and large portions of raw vegetables can cause bloating and GI distress right when you need your stomach cooperating.
A sample day at around 3,200 calories and 540 grams of carbs (about 8 g/kg for a 150-pound person) might look like this:
- Breakfast: A cup of oatmeal cooked in 16 oz of milk, topped with raisins and brown sugar, plus 12 oz of apple cider (roughly 175 g carbs)
- Lunch: A large baked potato with cottage cheese, baby carrots with hummus, and 12 oz of grape juice (roughly 160 g carbs)
- Snack: An extra-large banana with peanut butter (about 50 g carbs)
- Dinner: Two cups of cooked rice with chicken and green beans (about 100 g carbs)
- Dessert: Half a cup of dried pineapple (55 g carbs)
To push closer to the 10 to 12 g/kg range, you would add more carb-dense foods throughout the day: extra juice, a second serving of rice, honey on toast, or sports drinks between meals. Liquid carbs like juice, smoothies, and sports drinks are especially useful when you’re struggling to eat enough solid food. Fruit like bananas, grapes, watermelon, and cantaloupe also digest quickly and contribute carbs without excessive fiber.
What to Limit During the Load
Fat and protein aren’t the enemy, but they take up stomach space that you need for carbohydrates. Large portions of meat, fried foods, nuts, cheese, and oils will fill you up before you hit your carb target. Keep protein moderate (enough to maintain your muscles, roughly 1 to 1.8 g/kg) and let carbs dominate each plate. A small portion of chicken or fish at dinner is fine. A 16-oz steak with a side of buttered broccoli is not the move.
Avoid experimenting with new or unfamiliar foods during the loading phase. Stick with foods you know your stomach handles well. Spicy dishes, heavy cream sauces, and large salads are all worth skipping in the two days before competition.
Your Final Pre-Race Meal
The last meal before the race should contain no more than about 75 grams of carbohydrates and be eaten at least two hours before the start. A plain bagel with jam, a small bowl of cereal with milk, or a couple of pancakes with syrup all fit this window. The goal is topping off liver glycogen (which depletes overnight while you sleep) without flooding your stomach right before you need to perform.
Avoid eating a large dose of carbohydrates in the 30 to 60 minutes before the race starts. Consuming sugar in that window can trigger a rapid insulin spike followed by a blood sugar drop right as you begin exercising, leaving you feeling sluggish in the early miles.
Carb Loading for Women
Early research suggested that women didn’t respond to carb loading as effectively as men, but more recent evidence paints a clearer picture. Women can absolutely benefit from carb loading, though the menstrual cycle plays a role in baseline glycogen levels. During the early follicular phase (the first days of a period), resting glycogen stores tend to be lower. During the mid-luteal phase (roughly a week before the next period), glycogen levels are naturally higher regardless of diet.
The good news is that carb loading appears to overcome this difference. Women who loaded carbs during the follicular phase brought their glycogen stores up to levels comparable to the luteal phase. The practical takeaway: follow the same loading protocol regardless of where you are in your cycle, but be aware that you may need to be more deliberate about hitting your carb targets during the first half of your cycle.
During and After the Race
Carb loading fills the tank before the event, but for races lasting more than two and a half hours, you also need to refuel on the move. Current guidelines recommend consuming about 60 grams of carbs per hour for the first two and a half hours, increasing to up to 90 grams per hour beyond that. Some athletes push past 120 grams per hour, but tolerating that volume requires weeks of gut training beforehand.
After you cross the finish line, consuming carbs at a rate of about 0.8 to 1 gram per kilogram per hour helps replenish glycogen stores faster. This matters most if you have another event within 24 hours. For single-event athletes, just resuming normal meals over the following day will restore glycogen levels within 24 to 48 hours.