Pre-race nutrition maximizes performance by ensuring readily available energy, maintaining stable blood sugar levels, and minimizing gastrointestinal (GI) distress during the event. The body’s preferred fuel source for moderate to high-intensity exercise is carbohydrate, stored as glycogen in the muscles and liver. Optimal fueling involves careful timing and food selection to ensure glycogen stores are full and the digestive system is not stressed when the race begins. Since every person’s digestive system is unique, the most effective pre-race plan is always one that has been practiced during training—a concept often summarized as eating “nothing new on race day.”
Fueling the Day Before: Glycogen Storage
The 24- to 48-hour period before a race is when an athlete should focus on “carb loading,” which is the strategy of maximizing the storage of muscle and liver glycogen. Glycogen represents a finite fuel tank, and for endurance events lasting longer than 90 minutes, depleting these stores is a primary cause of fatigue. A full tank of muscle glycogen can power the body for up to two hours of moderate-intensity exercise.
To achieve this maximum storage, dietary carbohydrate intake should increase significantly, typically aiming for 10–12 grams per kilogram of body weight per day in the 36 to 48 hours leading up to the event. The focus should be on complex carbohydrate sources that are easily digestible and low in fiber, which helps prevent intestinal discomfort on race morning. Good choices include white rice, pasta, potatoes, and white bread.
Limit foods that slow digestion or contribute to GI issues, such as high-fat foods and high-fiber vegetables. The day before the race requires a temporary shift to a carbohydrate-centric menu with moderate protein. This strategy ensures the body’s primary fuel source is topped off without leaving residual food in the digestive tract.
Race Morning: The 3-4 Hour Meal
The meal consumed three to four hours before the race start serves to top off liver glycogen stores, which are partially depleted overnight. This timing allows for gastric emptying, ensuring the food is fully digested and the energy is available in the bloodstream. Eating a meal too close to the start can divert blood flow to the digestive system, which should be prioritized for working muscles.
The ideal composition of this pre-race meal is high in easily digestible carbohydrates, low in fiber and fat, and moderate in protein. Low-fiber carbohydrates prevent excessive bowel stimulation and discomfort, while minimal fat ensures rapid stomach emptying. For a 120-pound person, this meal might contain around 160 grams of carbohydrates and 20 grams of protein.
Specific, easily accessible food examples include oatmeal made with low-fat milk, white toast with jam, or a bagel with a small amount of peanut butter. The goal is a caloric intake of roughly 700 to 1,000 calories, depending on body size and event length, to provide sustained energy release without causing feelings of heaviness.
The Final Hour: Quick Energy and Hydration
In the final 60 minutes before the race, the body is no longer able to effectively process a complex meal, but a final small carbohydrate boost can be beneficial. This window is ideal for consuming simple sugars that bypass the slow digestive processes and provide a rapid energy source. A small intake of easily absorbed glucose, typically 30 grams, can prevent a drop in blood glucose, known as reactive hypoglycemia, which can occur as the body begins to transition to exercise.
Common choices for this final boost include sports gels, chews, or a small amount of fruit juice. These simple carbohydrates are designed for rapid assimilation into the bloodstream, making their energy immediately available. The strategy here is not to “load” but to provide a quick, readily available fuel source to complement the stored glycogen.
Hydration is also a major focus during the final hour, aiming to optimize fluid balance without over-drinking. Athletes should take small, steady sips of water or an electrolyte drink to ensure they start the race well-hydrated. Excessive fluid intake too close to the start can lead to sloshing or the need for frequent bathroom breaks; therefore, a measured approach to fluid consumption is necessary.
Foods and Habits That Cause GI Distress
Avoiding foods and habits known to irritate the gut is as important as consuming the right fuel in the 24 hours before a race. Gastrointestinal issues, often called “runner’s stomach,” are common in endurance athletes and can significantly hinder performance. High-fiber foods, such as beans, bran, and cruciferous vegetables like broccoli, are major culprits because they are indigestible and promote increased bowel movements and gas production.
Excessive fat and protein intake should also be limited, as they slow down gastric emptying, which can lead to bloating and nausea during exercise. Certain dairy products, spicy foods, and artificial sweeteners (particularly sugar alcohols) are known gut irritants that should be strictly avoided.
Trying any new food, supplement, or brand of sports nutrition product on race day carries a high risk of GI distress, as the body has not adapted to its specific composition. Stress and pre-race nerves can also independently contribute to intestinal urgency and discomfort. Sticking to a tested, low-residue diet is the most effective defense against race-day stomach problems.