Are carbohydrates good before a race?

December 10, 2025 •

4 min read

For endurance events over 90 minutes, proper carbohydrate loading can boost performance and endurance by 15-25%. Eating the right carbohydrates at the right time before a race is a crucial strategy to maximize your energy stores and finish strong.

Quick Summary

Carbohydrates are essential for fueling athletes, but the optimal type and timing depend on race duration. This guide explains how to use complex and simple carbs to maximize glycogen stores and provide sustained energy on race day, preventing fatigue.

Key Points

The Science of Carbohydrates and Performance: Carbohydrates are the body's main fuel source, converted to glycogen for energy during exercise. Depleted stores can cause fatigue.
Complex vs. Simple Carbohydrates: Timing dictates the carb type; complex for sustained energy 3-4 hours before, simple for quick boosts closer to the race.
Carb Loading for Endurance Events: For races over 90 minutes, increase carb intake 1-3 days prior and taper training to maximize glycogen stores.
What to Avoid Before a Race: Steer clear of new foods, high-fiber items, high-fat foods, and excessive protein to prevent stomach issues.
Comparison Table: The fueling strategy depends on race distance; shorter races require less intense carb management than marathons.
The Importance of Practice: Never experiment with new nutrition strategies on race day; test all food and drink during training runs.
Conclusion: Proper carbohydrate timing and type are crucial for optimal race performance, from a simple snack to a full carb load.

The Science of Carbohydrates and Performance

Carbohydrates are the body's primary and most efficient fuel source for high-intensity exercise. When you consume carbohydrates, your body converts them into glucose, which is then stored in the muscles and liver as glycogen. During a race, your body accesses these glycogen stores to power your muscles. The phenomenon known as "hitting the wall" occurs when these glycogen reserves become depleted, forcing your body to rely on less efficient fat stores for energy. Proper carbohydrate intake ensures you start with a full tank of fuel, delaying fatigue and maintaining performance.

Complex vs. Simple Carbohydrates: Timing is Everything

Not all carbohydrates are created equal, especially when it comes to race day fueling. The timing of your intake dictates whether you should reach for a complex or simple carb source.

The Pre-Race Meal (3-4+ hours before)

For the meal 3 to 4 hours before your race, the focus should be on easily digestible, complex carbohydrates. These carbs break down slowly, providing a sustained release of energy and topping off your liver and muscle glycogen stores.

Good examples include:
- White pasta with a simple tomato-based sauce
- Plain white rice
- Oatmeal
- Toast with a little jam
- Plain bagels
What to limit: High-fiber vegetables, fats, and protein should be limited in this meal as they can slow digestion and cause stomach upset during the race.

The Pre-Race Snack (1 hour or less before)

As you get closer to the start line, you need a quick-absorbing source of energy. This is where simple carbohydrates, or sugars, come in. They provide a rapid spike in blood glucose for an immediate energy boost.

Good examples include:
- Bananas
- Sports drinks
- Energy gels or chews
- Dried fruit, such as raisins or dates
Tip: Practice using these simple carbs during your training runs to determine what your stomach can tolerate on race day.

The Practice of Carb Loading for Endurance Events

For events lasting longer than 90 minutes, a strategy called carbohydrate loading is highly beneficial. This involves increasing your carbohydrate intake in the 1-3 days leading up to the race, while simultaneously tapering your training volume. This combination allows your muscles to maximize their glycogen storage capacity. Many athletes will notice a slight weight gain of 2-4 lbs during this period, which is extra glycogen and the water that binds to it—a sign that the loading is working. It is also crucial to stay hydrated, as water is needed for proper glycogen storage.

Comparison Table: Pre-Race Carb Strategy by Distance


Race Distance	Race Duration	Timing of Pre-Race Meal/Snack	Ideal Carb Types	Notes
5K / 10K	< 90 minutes	Standard meal 2-3 hrs prior; Optional snack <1 hr prior.	Complex carbs for the meal; Simple carbs for the snack.	Full carb loading is typically not necessary.
Half Marathon	~90+ minutes	Larger meal 3-4 hrs prior; Snack <1 hr prior; Consider fueling during.	Prioritize complex carbs; Include simple carbs before and during.	Practice fueling strategy during long training runs.
Marathon / Ultra	> 2 hours	Carb load 1-3 days prior; Large meal 3-4 hrs prior; Snack <1 hr prior; Fueling during.	Complex carbs for loading; Simple carbs for quick fuel.	Maximize glycogen stores and follow a strict fueling plan during the race.

What to Avoid Before a Race

While carbohydrates are your friend, not every food is ideal for race day. Avoid anything new or unusual that could cause gastrointestinal issues. Stay away from high-fiber foods, such as excessive amounts of beans, broccoli, or leafy greens, as well as high-fat foods and creamy sauces, which can all lead to discomfort. Even small amounts of dairy can be problematic for some. Stick to what you've tested and practiced during training to prevent unwelcome surprises.

The Importance of Practice

Finally, remember that race day is not the time to experiment. The most effective race strategy is one that has been fine-tuned during your training. Use your long runs to test your pre-race meals and snacks to see how your body reacts. Understanding your personal tolerance for different foods and fluid intake is key to a successful and comfortable race. By following a smart, practiced fueling plan, you can harness the power of carbohydrates and unleash your best performance. Fueling Your Run with Good Nutrition

Conclusion

Carbohydrates are unequivocally beneficial before a race, serving as the essential fuel to power your performance. For shorter events, a strategic meal and snack will suffice. For endurance races, carb loading is a proven technique to top off your energy stores. The key to success lies in knowing the difference between simple and complex carbs, timing your intake correctly, and avoiding foods that could cause stomach distress. Ultimately, a successful race-day nutrition strategy is developed and refined through consistent practice during training.

Frequently Asked Questions

Carb loading is generally not necessary for shorter races like a 5K, as your body's existing glycogen stores are sufficient. Focus on eating a balanced diet and a light, easily digestible carbohydrate-rich meal a few hours before the race.

For endurance events, a substantial, carb-focused meal should be consumed approximately 3 to 4 hours before the race to allow for proper digestion. For a quick top-up, a simple carb snack can be eaten less than one hour before.

Complex carbohydrates consist of long chains of sugar molecules that break down slowly, providing sustained energy. Simple carbohydrates are made of shorter chains, digesting quickly to offer a fast energy boost.

Consuming too much fiber before a race can cause gastrointestinal distress, including bloating, cramps, or diarrhea. It's best to reduce high-fiber foods in the 1-2 days leading up to your race, especially if you have a sensitive stomach.

Good pre-race meal options include white pasta with tomato sauce, plain oatmeal, a bagel with jam, or white rice with grilled chicken. These meals are high in carbohydrates and low in fiber, fat, and protein.

The weight gain associated with carb loading is mostly water weight. For every gram of glycogen stored, your body also stores about 3 grams of water. This is a positive sign that your muscles are properly fueled and hydrated.

For endurance races, the best strategy is to carb load over several days leading up to the event, with a significant carb-rich meal the night before. This is followed by a smaller, easily digestible carb breakfast on race morning.