Keto Diet For Runners: How Many Carbs To Eat?

The keto diet is a popular choice for people looking to lose weight. It involves limiting your intake of carbohydrates and upping your fat intake. For runners, however, the keto diet may not be the best option. This is because carbohydrates are a great source of glucose, which is the form of sugar that our brain, nerves, and muscles need to function. Distance runners, in particular, need more carbs than people who aren't training. This is because running uses both glucose in the blood and your stores of glycogen.

Runners need carbs for endurance

Runners need to ensure they are consuming enough carbohydrates to support their training and racing performance. While low-carb diets are popular for weight loss, they are not ideal for runners, who require carbs for endurance.

Carbohydrates for Energy

The body turns carbohydrates into glucose, which circulates in the blood and is stored in the liver and muscles as glycogen. This acts as the primary fuel for endurance exercise. When glycogen stores are depleted, runners are likely to "hit a wall" and run out of energy. Consuming carbs helps to prevent this by minimising glycogen depletion and keeping blood sugar levels stable.

The recommended daily intake of carbohydrates varies depending on the individual and their level of activity. Generally, runners should aim for 60-70% of their calories from carbohydrates, with lean protein and healthy fats each accounting for 15-20% of their remaining calories. During a run lasting over 90 minutes, runners should aim for 40-60 grams of carbohydrates per hour after the first hour of running. This helps to spare glycogen stores, maintain blood glucose levels, and replenish glycogen stores before the next training session.

Carb Loading

For casual runners, ensuring their daily diet includes extra carbohydrates may be sufficient. However, for those training for a marathon or distance event, carb loading is recommended. This involves consuming a high amount of carbohydrates in the 24-48 hours before the race to maximise glycogen stores and reduce the risk of burnout.

Timing of Carbohydrate Intake

The best time to eat a full meal is 2-3 hours before running, with a good source of carbs paired with protein. If it has been more than 3-4 hours since eating, a carbohydrate-rich snack 30 minutes before running can provide adequate glucose to power through the run. Directly before a run, easy-to-digest carbohydrates are best to avoid gastrointestinal issues.

Types of Carbohydrates

Runners should focus on healthy carbohydrates such as rice, whole grain bread and pasta, and oatmeal. Simple sugars like glucose and fructose are easily digestible and can provide a quick energy boost during long runs. Sports drinks, gels, and candies are also popular sources of carbs for runners.

Keto is not recommended for runners

The ketogenic (keto) diet is a popular eating regimen that involves limiting carbohydrates and increasing fat intake, with the aim of putting the body into a state of ketosis. While keto has been touted as an effective way to lose excess body fat and improve health, it may not be the best dietary approach for runners. Here's why:

Carbohydrates are Essential for Runners

Runners, especially those covering long distances, require an adequate intake of carbohydrates to fuel their endurance. Carbohydrates are broken down into glucose, which serves as the body's most accessible form of energy. By contrast, the keto diet restricts carbohydrate consumption to as little as 5% of total calories, replacing them with high amounts of fat. This can leave runners without the necessary energy stores to support their training and may lead to premature fatigue or "hitting a wall."

Negative Impact on Performance

Several studies have shown that a keto diet can negatively impact the performance of runners, particularly those engaged in high-intensity workouts or racing. For example, a study published in the Journal of the International Society of Sports Nutrition found that a 10-week keto diet resulted in a decline in the running speed and power of trained athletes. Similarly, another study in the journal Medicine & Science in Sports & Exercise reported a decrease in running speed at VO2 max by 5%. These findings suggest that keto may hinder the performance of runners, especially those aiming to improve their speed and power output.

Difficulty in High-Intensity Workouts

Keto diets have been associated with reduced energy levels, particularly during high-intensity exercises. In the short term, athletes may experience an initial drop in energy before their bodies adapt to using fat as the primary fuel source. This adaptation period can take several weeks, during which runners may struggle to maintain their usual training intensity. Additionally, the keto diet may not provide sufficient energy for runners who are used to higher-intensity workouts, potentially hindering their performance and progress.

Health Concerns

Undereating carbohydrates can have adverse health effects on runners, especially women. Dietitians have observed a tendency for female runners to over-exercise while not consuming enough calories, which can lead to vitamin and mineral deficiencies. For example, iron deficiency is a common issue, impacting running performance and overall health. Keto diets, by limiting carbohydrates, may exacerbate this issue and negatively impact the health of runners, especially if they are not careful about meeting their nutritional requirements through other food sources.

Gastrointestinal Issues

High-fat, low-carb diets like keto can also lead to gastrointestinal distress, including gas, bloating, and nausea. During ultra-marathons or prolonged exercise, changes in blood volume, heat stress, and hydration status can slow down gut motility, making it challenging for the body to handle large amounts of fat. This can result in gastrointestinal problems, which are a leading cause of dropouts in ultra-marathons. Therefore, keto diets may not be the best choice for runners aiming to optimize their digestive health and avoid gastrointestinal issues during endurance events.

Carbs are important for recovery

Carbohydrates are an important part of a runner's diet, and they play a crucial role in the recovery process. While protein is often touted as the most important nutrient for muscle recovery, carbohydrates are equally essential. The primary goal of an athlete's body after a workout is to replace glycogen storage, and eating carbohydrates helps increase plasma glucose and insulin concentration, enabling the body to resynthesize glycogen efficiently.

Replenishing Energy Stores

Running, especially long-distance running, relies heavily on carbohydrates for endurance. When you run, your body uses both glucose in the blood and glycogen stored in the liver and muscles as fuel. Eating enough carbohydrates ensures that these energy stores are replenished and ready to support your next training session. If these stores are depleted, runners are more likely to experience burnout or hit a wall during their runs.

Supporting Recovery

Carbohydrates are key to supporting the recovery process. Consuming carbohydrates after a run helps to restore muscle glycogen stores and provides essential nutrients to the body. This not only aids in recovery but also makes the athlete stronger and faster over time. The U.S. Olympic Committee Sports Dietitians and The Australian Institute of Sport recommend that athletes consume between 1 and 1.5 grams of carbohydrate per kilogram of body weight for optimal recovery.

Avoiding Cravings

Eating adequate carbohydrates as part of your recovery meal will help prevent cravings throughout the day. If you don't eat enough carbohydrates, your body will demand them, and you may find yourself reaching for less nutritious options to satisfy those cravings.

Keto Considerations for Runners

The ketogenic (keto) diet, which involves significantly limiting carbohydrate intake, is not typically recommended for runners. While keto can be effective for weight loss and managing type 2 diabetes, it can be challenging for endurance athletes. Distance runners require more carbohydrates than sedentary individuals, and under-eating carbs can negatively impact performance and recovery. However, some keto diets, like the cyclical ketogenic diet, include higher carb intake around high-intensity workouts, which may be beneficial for runners.

Runners should eat carbs before, during and after a run

The keto diet is a popular choice for people looking to lose weight. It involves eating a very low-carbohydrate diet and replacing those calories with fats. This puts the body into a state of ketosis, where it burns fat for energy instead of carbohydrates. However, the keto diet is not generally recommended for runners, who require carbohydrates for endurance.

Before a Run

The best time to eat a full meal is two to three hours before running. This meal should include a good source of carbohydrates and protein. If it has been more than three to four hours since your last meal, a carbohydrate-rich snack 30 minutes before running can ensure your body has enough glucose available. Good options include crackers, pretzels, or cereal.

During a Run

For runs longer than 75 minutes, runners need to consume carbohydrates to keep their energy levels up. Carbohydrates are the body's preferred source of fuel during exercise, and eating carbs during a run will help spare glycogen stores and keep blood sugar levels stable. Aim for 40-60 grams of carbohydrates per hour after the first hour of running. This can be in the form of sports drinks, gels, or even candy, such as gummy bears.

After a Run

Consuming a mix of carbohydrates and protein within the first hour after running is important for replenishing glycogen stores and supporting muscle recovery. Good options include a peanut butter and banana sandwich, a veggie burger on a bun, or a protein shake.

While the keto diet may be suitable for some endurance athletes running very long distances, most runners will benefit from including carbohydrates in their diet before, during, and after their runs to maintain energy levels and support optimal performance.

Carbs are the body's preferred fuel source

Carbohydrates are the body's preferred fuel source, and this is no different for runners. The body turns carbohydrates into glucose, which is used by the cells for energy. Glucose is a form of sugar that circulates in the bloodstream, while glycogen is the sugar stored in the liver and muscles, acting as the primary fuel for endurance exercise.

Runners need to ensure they have enough energy stores to support their training. When these stores get too low, runners are more likely to run out of energy and "burn out" or "hit a wall". Eating plenty of carbs helps ensure these energy stores are full and ready to support training.

The body can only store a limited amount of glycogen. When you deplete your stores, your muscles and brain run out of fuel, and you feel physically fatigued and mentally drained. "Hitting the wall" is essentially your brain and muscles running out of carbs. Consuming carbs can help minimise glycogen depletion and keep blood sugar levels stable, says sports nutritionist Deborah Shulman.

Runners need to be careful not to eat too many carbs mid-run, as this can lead to stomach issues. However, eating some carbs during a run will help athletes spare their glycogen stores, keep blood glucose from dropping, and help replenish glycogen stores before the next training session.

While low-carb diets are popular for weight loss, they are not ideal for runners, especially those running long distances. Very low-carb diets like keto can be dangerous for runners and are not recommended by experts unless advised by a doctor.

The number of carbohydrates a runner needs will depend on various factors, including the runner's size, fitness level, and the intensity and duration of their runs. Smaller runners might only need 100 calories every hour, while larger runners might need around 250. The less fit a runner is, the faster they will burn through stored carbs, so they will need more calories mid-run to keep their energy levels up.

During a run lasting over 90 minutes, glycogen stores can get drained, especially if the workout is moderate to high intensity. In this case, runners should aim for 40-60 grams of carbohydrates per hour (120-240 calories/hour) after the first hour of running.

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