Carb loading involves adjusting your diet and exercise levels for 1 to 3 days to boost the amount of carbs stored in your body. It may improve exercise performance, but it’s not necessary for all types of activities.
Carbohydrates are one of your body’s primary fuel sources. In the body, carbs are stored as glycogen, which is mostly found in the liver and muscles.
During moderate to high intensity workouts, your body uses these glycogen stores as its primary energy source.
However, your body can only store so much glycogen at once, and the stores become depleted throughout exercise as the energy is used to fuel it.
Carb loading is a nutritional strategy for increasing your body’s glycogen stores above the normal amount. It involves eating more carbs than usual and decreasing exercise for several days.
It may be beneficial for periods of high intensity exercise that last longer than 60 minutes, but for shorter bouts of exercise or less intense activities, carb loading may not be beneficial.
Keep reading to learn more about how carb loading works, different strategies, common mistakes, and the types of foods you should eat.
Carb loading involves increasing the ratio of carbs and glycogen stores in your body for 1 to 3 days prior to a long or high intensity event that’s likely to deplete your glycogen stores.
This may involve increasing the number of carbs you consume and lowering the amount of exercise you perform.
In general, experts recommend consuming around 10 grams (g) per kilogram (kg) of body weight (4.5 g per pound) of carbohydrates per day. So, if you weigh 70 kg (154 pounds), that equals 700 g of carbs per day.
Some experts previously used a percentage ratio, where 60% to 70% of the total calories were from carbohydrates. But this is no longer used, as caloric strategies range widely from person to person.
It’s important to note that while you may increase the amount of carbs in your diet, you’re not increasing the total amount of calories. When you increase the number of carbs, you will decrease proteins and fats, too.
Experts suggest that carb loading may primarily improve performance for certain types and durations of exercise.
Specifically, it may be appropriate for exercise that leads to large decreases in the amount of glycogen in your muscles. This may include high intensity endurance activities like cycling, running, or sports like soccer.
In these types of exercise, fatigue can occur when glycogen levels get too low. But research suggests that carb loading may help prolong energy stores, which means you can have energy for longer periods and delay fatigue.
An older 1997 study found that carb loading improved performance by
Carb loading may be beneficial for longer periods of high intensity exercise. But it’s unlikely to be effective for shorter durations of exercise or lower intensity exercises, such as weight training. This is because fat is the primary fuel source for these types of workouts.
There are several different types of carb loading, but all strategies involve increasing the number of carbs you eat and temporarily decreasing the amount you exercise.
Here are the two most common protocols:
Classic 6-day
The classic 6-day carb load strategy was first developed in the 1960s. It’s designed to completely deplete glycogen stores during the first 3 days, then eat high amounts of carbs over the next 3 days to saturate the stores.
- Days 1 to 3: A low carb diet, where 5% to 15% or 100 g of your calories come from carbs, is combined with high intensity exercise.
- Days 4 to 6: A high carb diet, where more than 70% or 500 g of daily calories come from carbs, is combined with low intensity exercise.
Although experts once believed the initial “depletion” phase helped the body produce more glycogen once carbs were eaten again, research from 2017 shows it may not be necessary.
Classic 2- to 3-day
Healthcare professionals now recommend a carb loading phase of 36 to 48 hours before the high intensity event. The number of carbs this typically involves consuming is 10 to 12 g per kg (4.5 to 5.5 g per pound) of body weight.
Some people also consume a low residue diet for 3 days before the high intensity event to help limit possible gastrointestinal symptoms. This diet limits high fiber foods that may be hard to digest and leave “residue” in your digestive tract after early digestion stages.
Before you start a carb loading program, there are several common mistakes you should be aware of.
Carb loading when you don’t need to
Research suggests that carb loading may be beneficial for people getting ready to perform a high intensity activity that lasts longer than 60 minutes, such as a running or cycling race.
When it comes to shorter durations and intensities of exercise, carb loading may not provide any benefits.
For instance, a 2022 review found that carb loading is most likely not beneficial for weight lifting, unless lifting at high volumes. This means performing more than 10 sets per muscle group in one session.
Carb loading when you don’t need to may also lead to consuming more calories than your body needs.
Consider the type of activity you’re doing and whether carb loading may be beneficial. If you’re unsure, speak with a registered dietitian, athletic coach, or healthcare professional. They can help you decide the pros and cons of carb loading for you.
Eating the wrong amount of carbs
Not getting enough carbs during an intended carb loading phase may affect your performance on the event day, while eating too many carbs may lead to eating too many calories, unintended weight gain, or a change in your diet.
To determine how many carbs to eat during a carb loading phase, start by calculating your daily carb intake by recording all the food you eat for several days using a food-tracking app or the nutrition labels on your food.
Then you can divide the grams of carbs you eat each day by your weight to compare your current intake to carb loading recommendations.
For example, if you weigh 70 kg (154 pounds) and you normally eat 300 g of carbs per day, then you’re consuming 4.2 g per kg (1.9 g per pound) of carbs per day.
Experts recommend eating around 10 g of carbs per kg (4.5 g per pound) of body weight per day during a carb loading phase. Based on these recommendations, you would need to eat more than double the amount of carbs you would normally.
Eating too much fat
Fat is an important macronutrient in a balanced diet.
While more research is needed to understand the role of fat in carb loading, it may be beneficial to limit the amount you eat to avoid eating too many calories and feeling sluggish.
That said, a
A registered dietitian could help you determine how much fat you should eat during your carb loading phase.
Eating too much fiber
Some people report that eating high fiber foods during a carb loading phase may increase the risk of experiencing gastrointestinal symptoms like stomach discomfort, bloating, and water retention during the sporting event.
Carb loading is a unique time when it may be better to choose refined grains like white bread or pasta over whole wheat.
Exercising too much
Lastly, failing to decrease or “taper” the amount of exercise you perform during carb loading could limit the extent to which your glycogen stores increase during your high carb diet.
A personal trainer or registered dietitian could help you determine the best type, duration, and intensity of exercise to perform during a carb loading phase.
To get the recommended amount of carbs, you should focus on foods that are high in carbs, low in fat, and don’t have too much fiber.
The table below highlights some foods to consider eating and limiting during your carb loading phase:
| Foods to eat | Foods to limit |
|---|---|
| • low fiber cereals • 100% fruit juice • white noodles with marinara sauce • white bread • fruit jelly • white rice • fruit smoothies • skinned white potatoes • applesauce • pretzels • bananas • oranges • watermelon • white flour, used in cooking • sherbet or popsicles • sports drinks • low fat energy bars | • creamy sauces • muffins • chips • cookies • pizza • brownies • ice cream • pastries • french fries • donuts • high fiber energy bars • beans • lentils • split peas • whole wheat products • bran flakes • oatmeal • raspberries • artichoke • green peas • chickpeas • chia seeds • broccoli |
It’s important to continue eating protein and healthy fats to help support your muscles. Try to focus on lean protein sources, such as fish, lean cuts of meat or poultry, and low fat dairy.
What’s more, eat foods you enjoy and that are familiar to you.
Carb loading is a nutrition strategy to help increase the glycogen stores in your body, which can lead to increased athletic performance during high intensity exercise that lasts longer than 60 minutes.
A carb loading phase usually lasts 1 to 3 days and involves eating around 10 g of carbs per kg (4.5 g per pound) of body weight daily.
This strategy may not be useful for you if you are recreationally active but not an athlete or competitor in long-duration events.
If you’re unsure whether carb loading is right for you, consider speaking with a healthcare professional, registered dietitian, or personal trainer. They can develop the best strategy to maximize your health and fitness goals.
