Carbohydrates are the fuel that powers a runner’s stride, dictating endurance, speed, and overall performance. Without a proper carb intake, even the most well-conditioned athletes will find themselves struggling to maintain pace, feeling sluggish, or, worse, hitting the dreaded wall. Running demands a high level of energy, and the body relies on stored glycogen—derived from carbohydrates—to sustain prolonged effort. The key to maintaining optimal energy levels lies in choosing the right types of carbohydrates, timing intake appropriately, and understanding how different sources affect performance. Jeff Derderian explains that carbohydrates serve as the body’s most efficient energy source, making them essential for runners looking to maintain consistency in training and peak performance on race day.
Understanding Glycogen and Energy Storage
Carbohydrates are converted into glucose, which the body uses for immediate energy. Any excess glucose is stored as glycogen in the liver and muscles, acting as a reserve for later use. These glycogen stores are critical for endurance athletes, as they determine how long a runner can sustain effort before fatigue sets in. The body has a limited capacity for glycogen storage, which is why strategic fueling is necessary to maximize these reserves.
During moderate to high-intensity runs, the body primarily burns glycogen for fuel. Once these stores become depleted, fatigue sets in, and performance declines rapidly. Unlike fats and proteins, which require more energy to break down, carbohydrates offer a readily available source of fuel, making them the most efficient macronutrient for endurance sports.
Choosing the Right Carbohydrates
Not all carbohydrates are created equal. Simple carbohydrates, found in foods like fruit, honey, and refined sugars, provide quick energy but can lead to rapid spikes and crashes in blood sugar levels. These are best used immediately before or during a run when the body needs instant fuel.
Complex carbohydrates, found in whole grains, vegetables, and legumes, offer a slower, sustained release of energy. Because they take longer to digest, they help maintain steady blood sugar levels and provide endurance athletes with a reliable source of fuel over a longer period. Balancing both simple and complex carbohydrates ensures that a runner has both immediate and long-lasting energy available throughout training and races.
Pre-Run Carb Loading: Does It Work?
Carbohydrate loading is a strategy used by many distance runners to maximize glycogen stores before a long race or intense training session. The process involves gradually increasing carb intake in the days leading up to an event while tapering exercise intensity. This allows muscles to store more glycogen than usual, delaying fatigue and improving endurance.
The effectiveness of carb loading depends on the type and duration of the run. For shorter distances, such as a 5K or 10K, a normal carbohydrate intake is sufficient. However, for marathons and ultramarathons, increasing carb consumption in the days leading up to the event can significantly improve performance by ensuring muscles have adequate fuel to sustain prolonged exertion.
What to Eat Before a Run
Timing carbohydrate intake before a run is crucial to ensuring the body has enough fuel without causing digestive discomfort. Eating a meal rich in complex carbohydrates, such as oatmeal, whole-grain toast, or brown rice, about two to three hours before a run provides a steady release of energy.
For those who need a pre-run snack closer to the workout, easily digestible options like a banana, a slice of toast with honey, or an energy bar can offer a quick boost without causing stomach issues. The key is to avoid high-fiber or excessively fatty foods before running, as they take longer to digest and can lead to discomfort.
Fueling During a Run
For runs lasting less than an hour, the body typically has enough stored glycogen to sustain effort without additional fueling. However, for long-distance training and races, consuming carbohydrates during the run is essential to maintaining energy levels and avoiding glycogen depletion.
Fast-digesting carbohydrates like sports drinks, gels, and chews provide an immediate source of glucose, helping runners sustain their pace without experiencing a sharp decline in energy. Some runners prefer real food options such as dried fruit, pretzels, or even small bites of peanut butter and jelly sandwiches, but the most important factor is finding what works best for the individual’s digestive system.
Post-Run Recovery: Replenishing Glycogen Stores
After a run, the body needs to replenish glycogen stores and repair muscle tissue. The first 30 to 60 minutes after exercise is considered the optimal window for refueling, as muscles are more receptive to absorbing nutrients. Consuming carbohydrates paired with protein helps speed up recovery and ensures that glycogen stores are restored for the next workout.
Good post-run carbohydrate sources include sweet potatoes, whole-grain pasta, quinoa, or a smoothie with fruit and yogurt. Including a source of protein, such as lean meat, eggs, or plant-based alternatives, helps support muscle repair and reduces soreness. Hydration is also essential, as the body loses electrolytes through sweat, which need to be replenished for proper recovery.
The Impact of Carbohydrates on Performance
Carbohydrates not only provide fuel but also play a role in overall running performance. Athletes who consistently meet their carbohydrate needs experience better endurance, reduced muscle fatigue, and faster recovery times. On the other hand, those who fail to consume enough carbohydrates may suffer from energy crashes, slower paces, and longer recovery periods between workouts.
Studies have shown that runners who properly fuel with carbohydrates before and during a race perform better than those who rely solely on fat or protein for energy. Glycogen depletion leads to a drop in blood sugar levels, which can result in dizziness, sluggishness, and a decline in mental focus—all of which are detrimental to performance.
Balancing Carbohydrates with Overall Nutrition
While carbohydrates are essential for runners, balance remains key. Over-reliance on refined or processed carbs can lead to energy fluctuations and digestive discomfort. Including a variety of nutrient-dense carbohydrate sources, such as whole grains, fruits, and vegetables, ensures that the body receives not only energy but also important vitamins, minerals, and fiber.
Additionally, hydration plays a significant role in carbohydrate metabolism. Dehydration can impair the body’s ability to efficiently use stored glycogen, making it even more critical to maintain proper fluid intake before, during, and after running. Electrolytes, particularly sodium and potassium, also support muscle function and should be included in a well-rounded fueling strategy.
Final Thoughts
Carbohydrates are the cornerstone of an effective fueling strategy for runners. From maximizing glycogen stores to sustaining energy during a run and supporting post-exercise recovery, the right balance of carbohydrates can make a significant difference in performance and endurance. By choosing nutrient-dense, high-quality carbohydrate sources and timing intake appropriately, runners can optimize their training and race-day performance while avoiding the pitfalls of energy depletion. Understanding how carbohydrates work allows athletes to make informed fueling decisions that enhance their ability to perform at their best.