Carbo Loading for Marathons: What to Eat and When

• It is essential that you take on enough energy before a half or full marathon by loading up on carbohydrates, which will help ensure the race goes to plan and that you don’t hit the wall.
• The main sources of energy used during a marathon are carbohydrates and fats. Which of those two we depend on more is reliant upon our running speed or intensity.
• Carbs that we eat prior to a race should be easily digestible and low in fiber, for instance, white bread and white rice, meaning that we should avoid carbs that are high in fiber, such as brown rice and whole wheat bread.a

In addition to training, the food we eat or the energy we take on plays a crucial role in preparing our body to run long distances. Many long-distance runners will be aware that before running a half or full marathon, it is necessary to load up on carbohydrates. This way of thinking comes from the basic facts involved with how the body uses up its energy stores, with the main stores that marathon runners rely upon are carbohydrates and fats. Which of these stores we primarily use during a race depends entirely on the speed or intensity that we run at. The faster we run, the more carbohydrates are used.

When running, we generally use carbohydrates that are stored as glycogen in our muscles and liver. When our glycogen stores are empty, the body turns to its fat stores, yet the body must work harder to process this form of energy which is why we begin to “hit the wall”. Hence, carbo loading correctly can help ensure our race goes to plan, removing any walls that could potentially hold us up.

There are numerous recommended methods regarding how we load up on carbs before a race. Some like to load up for the whole week prior to the event, while others will eat anything and everything they can get their hands on to ensure their energy stores are topped up. However, the most effective way to carbo load is detailed below.

Dr. Wilson and his team of researchers looked at 46 marathon runners, studying each of their eating habits for the three days leading up to their race, including during the race itself, at the same time as analyzing their respective body states throughout. They found that only the carbohydrates they ate on the day before and on the morning of the race itself had an impact on the time they took to complete the distance (the runners who ate the most were the fastest). Therefore, the 24–36 hours prior to a race are vital in terms of carbo loading.

Carbo loading before this critical time period may not only result in excess body weight (don’t forget you’ll need to carry any excess weight for the whole 42.195-kilometer race) but could also result in stomach and digestive issues.

The food we eat at this crucial time should not just be a buffet of anything we can get our hands on as we do not actually require an increase in calorie intake. We should merely be replacing our normal diet with around 85–95% carbohydrates, ensuring that any carbohydrates taken on are easily digestible and low in fiber, for instance, white rice and white bread. Avoid any carbs that are high in fiber, such as brown rice or whole wheat bread, because these will be more difficult to digest.

It is recommended that marathon runners eat their final large meal around 12 hours prior to the start of the race to ensure the body has time to transform the food into glycogen stores. Then, around 3–4 hours before the race, additional easy-to-digest carbs should be taken on to ensure those stores are topped up.

Simply put, if our race begins at 4 a.m., we should be loading up before 4 p.m. the previous day and eat a light breakfast after we wake up for the race. By following this advice, I am certain that you’ll all have a full tank of energy ready at the start line of your next big race.