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Carb Loading Before A Marathon: Tips, Errors To Avoid, And Foods To Eat

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Avoid hitting the dreaded wall by fueling correctly.

A prerace pasta dinner is often provided the night before many marathons and halfs for a reason: Having a sufficient amount of carbohydrates is crucial for maximizing your performance.

Many runners are familiar with the concept of consuming pasta, rice, potatoes, or other high-carb foods prior to a half or full marathon, as carbohydrates are known as a valuable energy source required to cover long distances of 42 km or 21 km. However, there is often confusion among runners regarding the appropriate quantity of carbohydrates to consume and the ideal time to begin carbohydrate loading.

Carb Science

When you consume a bowl of spaghetti, the majority of the carbohydrates are stored as glycogen in the muscles and liver. Glycogen is the body’s primary readily-available energy source, although it is not the sole source, according to Ryan. During a half or full marathon, both glycogen and fat are utilized for energy expenditure. However, fat is not as efficient, requiring extra effort for conversion into fuel by the body.

When glycogen is depleted during a race, you experience “the wall,” causing your body to decrease its pace while it converts fat into energy. Benjamin Rapoport, M.D., Ph.D., a 2:55 marathon runner, became very familiar with this phenomenon when he experienced it at the 2005 New York City Marathon. Subsequently, he decided to conduct research on ways to prevent hitting the wall in future races.

He says that carb-loading in the right way, which means filling your muscles with glycogen, will not result in increased speed, but it will enable you to perform at your highest level during running and, if you strategize well during a race, prevent hitting a physical and mental wall.

Who Should Carb Load

Carb-loading involves a systematic approach. It can be smoothly performed (please pass me the bread), but not all races necessitate this practice.

According to Pamela Nisevich Bede, R.D., a sports dietitian and co-author of Run to Lose, shorter distances like 5Ks or 10Ks do not require fueling as it is unlikely that you will exhaust the energy in your muscles within the time it takes to complete those distances. However, if you plan on running for more than 90 minutes, it is important to be proactive about fueling.

Choose Your Carbs Wisely

Sports nutritionist Ilana Katz, R.D. advises that while many fruits are high in carbs, they are also high in fiber which can lead to stomach issues during a race. To mitigate this, Katz suggests that bananas are a low-fiber option and recommends removing the peel from apples, peaches, and pears to reduce their fiber content. Additionally, she grants her clients the freedom to enjoy white bread and baked potatoes without the skin as they are easily digestible.

Michael Scott’s fettuccine Alfredo carb-loading did not turn out well in The Office for a reason: While the pasta contributed carbs, the rich, fatty sauce caused significant issues.

According to Ryan, high-fat foods like oils, butter, and cheese, and foods high in protein, make you feel full quickly and take longer to digest compared to carbohydrates. This can result in a heavy feeling in your stomach and potentially cause significant gastrointestinal issues during a race.

Quick tips for effective carb loading 

Calculate the daily amount of carbohydrates you require.

To achieve an effective carb load, it is suggested to consume 8-10 grams of carbohydrate for each kilogram of bodyweight per day. One kilogram is equivalent to 2.2 pounds. To determine your daily carbohydrate requirements during the carb load, multiply your bodyweight in kilograms by 8. For instance, a runner weighing 150 pounds (68 kg) would calculate their daily carbohydrate intake as 8 multiplied by 68, which equals 544 grams.

In preparation for a marathon, it is advisable to engage in a carb load that spans approximately 2.5-3 days.

To ensure optimal performance in the race, it is recommended to gradually increase your carbohydrate consumption three days prior to the event. If your marathon is scheduled for Sunday, the ideal timeframe to commence the intake of your targeted carbohydrate amount would be Thursday, Friday, and Saturday. For the aforementioned runner, the daily carbohydrate consumption for each of these three days would amount to 544 grams.

To ensure a balanced intake, distribute the carbohydrates evenly across meals and snacks.

When carb loading, it is important to consume a large quantity of food. It is recommended to distribute these carbohydrates evenly throughout the day, with the goal of having three main meals and two to three snacks.

Choose simple carbohydrates

The reasoning behind this is twofold. Firstly, glycogen is able to store simple carbohydrates more efficiently. On the other hand, starchy carbohydrates and fructose are stored with less efficiency, specifically fructose needs to be converted into glucose in the liver before it can be stored.

Additionally, although it is important to consume fiber for regularity, increasing the consumption of high-fiber carbohydrates will also lead to an increase in fiber intake. Consuming excessive amounts of fiber before an endurance event is not recommended, as it may heighten the chances of experiencing bathroom breaks or gastrointestinal discomfort during the race.

Increase the amount of fluid consumed.

In order to store glucose as glycogen, water is necessary. Moreover, this will aid in keeping yourself hydrated prior to running the marathon.

Counting liquid calories is necessary when thinking step by step.

If you are finding it difficult to consume a large amount of food, consider incorporating liquid calories into your diet. This can be done by consuming sports drinks and juices, as they contain carbohydrates.

Stay away from foods that are high in fat.

Even though cookies, cakes, and fries are attractive, they are not the best options for carb-loading. While they are tasty and do have carbohydrates, their high fat content means they have a lower amount of carbs per ounce. To illustrate, cookies and cakes only have 20-50% carbs while bagels, potatoes, and pretzels have 70-90% carbohydrates.

Foods that are best for carb loading

Your best choice is bland, simple carbohydrates. Stick with foods that are familiar to you and avoid any triggers if you have allergies.

  • Breads and bagels
  • Pretzels (hard and soft)
  • White rice
  • Potatoes (baked, boiled, roasted)
  • Bananas
  • Pasta and rice noodles
  • Graham crackers
  • Fig bars
  • Tortillas
  • Oats

Carb loading errors to avoid 

The way in which you carb load is important. It is possible to make some common mistakes, such as overdoing carb loading, which can cancel out the benefits and make you feel heavy and slow.

Overindulging in food

When carb loading, it is important to remember that it does not give you permission to overeat and consume sugary foods in large quantities. You are still providing your body with fuel to enhance its performance. While it is necessary to increase your carb intake, it should not be excessive to the point of causing feelings of bloating, sickness, and sluggishness.

Limiting oneself to a consumption solely comprised of carbohydrates.

Although you may consume a higher amount of carbohydrates, it is not advisable to solely rely on carbs for your diet. In case you experience discomfort while consuming a large amount of carbs, it would be beneficial to incorporate protein or fat alongside your carbohydrate intake. While you may slightly reduce your overall consumption, carbohydrates will still remain a part of your diet.

Deliberate exhaustion

The need to intentionally deplete carbohydrate stores before a carb load by engaging in a lengthy workout and following a low carb diet, as was traditionally practiced, is now considered unnecessary. This practice originated from research conducted in the 1960s, which focused on inactive individuals.

On the contrary, runners gradually use up their carbohydrate reserves during training sessions. The body adjusts to enhance its capacity to store glycogen. Moreover, abruptly transitioning to a low-carb diet can lead to feeling moody and fatigued shortly before the race, which is not the desired state.

Not consuming an adequate amount of water.

In order to effectively store glycogen, your body needs water. If you do not consume sufficient fluids, carb loading may not yield the desired results. Moreover, entering a marathon while slightly dehydrated is not ideal.

The act of being concerned about one’s weight

It is advised to avoid stepping on the scale as carb loading may temporarily cause an increase in water weight. This is because storing additional glycogen also requires storing extra water in the muscles. However, the advantages of carb-loading are highly beneficial. It is important not to excessively concern yourself with your weight.

is not a good idea because it increases the chances of feeling unprepared and overwhelmed.

Similar to how studying for an exam is ineffective, cramming is also not a productive method for carb loading. Consuming a large and dense meal the evening prior to the marathon can enhance the likelihood of experiencing gastrointestinal issues on the day of the race. Instead, it is recommended to distribute the intake of carbohydrates evenly throughout the entire day preceding the race.

How Much Should You Eat

According to Monique Ryan, R.D., author of Sports Nutrition for Endurance Athletes, it is not possible to fully replenish muscle glycogen with just one meal. That is why it is recommended to start carbo-loading two or three days prior to a race. As you are running a low distance, the glycogen will gather in your muscles.

According to Katz, it is advisable to obtain 85 to 95 percent of your calorie intake from carbohydrates. Ryan suggests consuming approximately 9 grams of carbohydrates for every kilogram of body weight. To illustrate, a runner weighing 68 kilos should consume 600 grams of carbohydrates, which is equivalent to 2,400 calories, on a daily basis.

While conducting his research, Rapoport created a more accurate formula that considers variables like age, resting heart rate, VO2 max, and predicted finish time. It should be noted that your daily calorie intake probably does not increase significantly compared to when you were in the midst of your training; the difference lies in the fact that a greater proportion of those calories come from carbohydrates.

If you step on the scale while you are consuming a lot of carbohydrates, expect to see a weight that is at least 2 kilos higher than your usual weight. The additional kilos indicate that you have successfully loaded up on carbs. According to Katz, for every gram of stored carbohydrate, you also store an extra 3 grams of water. This results in your body being well-hydrated and fueled when you begin the race, guaranteeing that you will finish feeling strong.

Top off your tank

If races can be completed in under 90 minutes, there is no need to load up on carbs before the event. However, races lasting over 60 minutes may necessitate an additional energy boost during the race.

Bede states that to efficiently fuel your body during exercise, consuming a sports drink, energy gel, or energy chew is one of the best approaches. These products provide carbs in the form of simple sugars, which are the preferred source of quick fuel for your body. Additionally, products that contain both glucose and fructose, two types of sugars, are absorbed at an even faster pace.

To replenish your glycogen stores during runs lasting 60 minutes or more, consume a drink, gel, or chew every 30 to 45 minutes. Aim for 120 to 240 calories, or 30 to 60 grams of carbohydrates. Additionally, these options often contain electrolytes, which help maintain fluid balance, and caffeine, which can enhance endurance during the final stretch of your run.

Is carb loading effective 

The reason why a carb load is advocated by most coaches is because it is effective in reducing the likelihood of hitting the wall, which is why a majority of elite runners increase their carbohydrate intake in the two to three days before a marathon.

Although some runners consider fat adaptation as an alternative, there is currently no research suggesting that it enhances performance in the marathon distance. While it would provide the necessary energy to complete the marathon, it would negatively affect your speed.

The International Journal of Sports Medicine conducted a study on the impact of carb loading on runners during the 2009 marathon. The study did not take place in a controlled laboratory setting, but instead observed runners in real-world conditions. Consequently, the study provides valuable insights into the effects of carb loading.

Out of the 250 marathons that were analyzed, it was discovered by the researchers that individuals who consumed over 7 g of carbohydrates per kg of body weight the day prior to the race ran at a speed approximately 13.4% higher compared to those who did not engage in carb loading. Achieving a 13.4% faster time in a marathon is considered to be a substantial improvement!

The effectiveness of carbo-loading during marathon training is attributed to the metabolic adaptations resulting from endurance training, which deplete a significant portion of glycogen (stored carbohydrates) during long runs.

As a consequence of this, your body adjusts to enhance its capacity to store glycogen. When race day approaches, your body can store a greater amount of glycogen compared to before. The combination of carb loading and the marathon taper enables you to fully utilize this training adaptation during the race.

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