Should I Eat Carbs or Protein Before a Race?

November 22, 2025 •

5 min read

According to the International Society of Sports Nutrition (ISSN), carbohydrates are the body's primary fuel for high-intensity exercise. When considering if you should eat carbs or protein before a race, the answer overwhelmingly points to prioritizing carbohydrates to ensure optimal performance and energy availability.

Quick Summary

Carbohydrates are the main energy source for high-intensity exercise, so they should be prioritized before a race. Protein is more critical for muscle repair and recovery after the race, though a small amount can help stabilize blood sugar if consumed hours beforehand. Timing and digestibility are key to avoiding gastrointestinal issues.

Key Points

Carbs are Primary Fuel: Carbohydrates are the most efficient energy source for high-intensity race efforts, as they are stored as glycogen in your muscles.
Timing is Key: Eat a high-carb, moderate-protein meal 2-4 hours before your race for digestion. Switch to simple, easily digestible carbs (like a gel or banana) within an hour of the start.
Practice Your Fueling: Never try new foods or drinks on race day. Test your race-day nutrition strategy during your long training runs to see what works best for your body.
Protein's Role is Recovery: While a small amount of protein can be beneficial in your pre-race meal, its primary function is muscle repair and rebuilding after the race, not providing immediate fuel.
Avoid GI Distress: To prevent stomach issues, avoid high-fiber, high-fat, and excessive protein close to race time, as these slow digestion.
Hydrate Smart: Don't forget hydration. Sip water and/or electrolyte drinks in the hours leading up to the race to start properly hydrated.

The Core Principle: Carbohydrates are King

For any high-intensity or prolonged endurance event, your body's primary and most efficient fuel source is glycogen, which is stored in your muscles and liver and derived from carbohydrates. A full tank of glycogen is crucial for sustaining a high output and preventing premature fatigue, often referred to as 'hitting the wall'. While fat can also be used as fuel, it is not as readily available or efficient during intense efforts. Protein, on the other hand, is not a significant fuel source during a race but is vital for muscle repair and rebuilding in the recovery phase afterward. Therefore, your pre-race meal strategy should focus heavily on maximizing your carbohydrate stores.

Race-Day Timing and Macronutrient Ratios

The timing of your pre-race meal is just as critical as its composition. Your body needs sufficient time to digest food and convert it into usable energy without causing gastrointestinal distress during the race. This is where the distinction between what to eat and when becomes important.

2-4 Hours Before the Race: For your final substantial meal, focus on a high-carbohydrate, moderate-protein, and low-fat mix. A little protein can help stabilize blood sugar, but too much can slow digestion and cause discomfort. Aim for 2 to 4 grams of carbs per kilogram of body weight during this window. Examples include oatmeal with a banana and nut butter, or a bagel with honey and a small amount of low-fat Greek yogurt.
60 Minutes or Less Before the Race: As the race start approaches, you should shift to easily digestible, simple carbohydrates. This provides a quick boost of energy without requiring significant digestive effort. This is not the time for protein or fat, which could sit heavily in your stomach. Fruit, energy gels, or a sports drink are excellent options here.
Carb-Loading Days Before the Race: For longer endurance events like a marathon, the strategy begins 36-48 hours prior. A carb-loading protocol involves increasing your carbohydrate intake to 10-12 grams per kilogram of body weight per day while tapering your training. This maximizes your muscle glycogen stores for race day.

The Role of Protein

While not the primary fuel for the race itself, protein plays a crucial supporting role. Consuming a moderate amount of protein in your meals in the days leading up to the race, and in your larger meal a few hours before, can help promote muscle protein synthesis and prevent muscle breakdown. This is especially important during heavy training weeks. However, the real work for protein starts after the race is over, when it is needed for muscle repair and recovery.

What to Avoid on Race Day

The golden rule of race-day nutrition is to stick with what you know. Never experiment with new foods, drinks, or supplements on the day of the event. Beyond that, several types of food should generally be avoided:

High-Fiber Foods: Foods like bran muffins, high-fiber cereals, and many raw vegetables can cause gastrointestinal distress and unwanted bathroom stops during a race. Stick to low-fiber carb sources in the hours before the start.
High-Fat Foods: Fats take longer to digest than carbohydrates, meaning they can sit in your stomach and cause discomfort, sluggishness, and bloating.
Excessive Protein: While a little protein is beneficial, too much can also slow digestion and is not an efficient fuel source for the race itself.
Sugar Alcohols and Artificial Sweeteners: Some athletes are sensitive to these, and they can cause digestive issues. It's best to avoid them unless you know for sure they don't affect you.

Practical Pre-Race Meal Examples

Here are some examples of pre-race meals and snacks, categorized by the timing leading up to your event:

Early Morning Meal (2-4 hours before): Oatmeal with a banana and a tablespoon of peanut butter; bagel with honey; white rice with grilled chicken breast and a small amount of vegetables.
Late Pre-Race Snack (1 hour or less before): Energy gel or chew; handful of pretzels; banana.
Hydration: Don't forget fluids. Sip water and/or a sports drink in the hours before the race to ensure you are well-hydrated, but avoid chugging large amounts close to the start to prevent a sloshy feeling.

Carbs vs. Protein Pre-Race: A Comparative Breakdown


Feature	Carbohydrates	Protein
Primary Function	Energy for high-intensity exercise	Repair and rebuild muscle tissue
Pre-Race Timing	Crucial, especially 36-48 hours before long events and in the final hours/minutes	Beneficial in moderate amounts 2-4 hours before, minimal closer to start
Optimal Intake (Pre-Race)	High intake to maximize glycogen stores (especially for longer races)	Moderate intake 2-4 hours pre-race to stabilize blood sugar; minimal just before
Digestion Speed	Fast-acting, especially simple carbs	Slower digestion; high amounts can cause GI issues
Avoidance	High-fiber versions right before the race (to prevent GI issues)	High amounts, especially close to the race start (due to slow digestion)
Race Day Examples	Bagel, oatmeal, rice, energy gels, sports drinks, bananas	Nut butter, low-fat yogurt, lean chicken

The Race is Won in the Kitchen

Your race-day performance is not solely determined by your physical training but is heavily influenced by your nutritional preparation. Prioritizing carbohydrates in the final days and hours before a race ensures your body has a full energy tank to power through the entire event. While protein is a vital part of your overall diet, its main contribution to race day performance is indirect and is more critical for post-race recovery. By strategically timing your meals, you can fuel your body effectively while avoiding the digestive pitfalls that can derail a strong performance. For personalized advice, it is always recommended to work with a registered sports dietitian to fine-tune your nutrition plan.

Conclusion: Fueling Smart for Success

To optimize your performance on race day, the key is to prioritize carbohydrates to top off your glycogen stores. Start your carb-loading in the days leading up to the race for longer events, and focus on an easily digestible, carb-rich breakfast 2-4 hours beforehand. As the start time draws near, switch to simple carbs for a quick energy boost. While protein is an important part of your diet, its main function is recovery, not pre-race fuel. By practicing your nutrition strategy during training, you can arrive at the starting line confident and properly fueled for your best performance.

Carbohydrates and endurance exercise: a summary of recent literature

Frequently Asked Questions

For a larger pre-race meal, aim for 2 to 4 hours before the race to allow for adequate digestion. If you need a quick energy boost closer to the start, a small, simple carbohydrate snack can be eaten 30 to 60 minutes beforehand.

For a shorter race (under 60 minutes), your body has enough stored glycogen to power you through, so a pre-race meal may not be necessary. If you do eat, focus on simple carbohydrates. A larger amount of protein is not needed for fuel and may cause stomach discomfort.

Carb-loading is a strategy for endurance athletes competing in events longer than 90 minutes. It involves consuming higher-than-normal carbohydrate intake for 1-2 days before the race to maximize glycogen stores in your muscles and liver. It is not necessary for shorter races like a 5K or 10K.

Consuming too much protein close to your race can cause digestive issues. Protein takes longer to digest than carbohydrates, and excess protein can lead to bloating, discomfort, and a heavy feeling in your stomach that negatively impacts your performance.

Good options include oatmeal with fruit, a bagel with honey or jam, or white rice with a lean protein source. Focus on easily digestible, lower-fiber carbs to avoid gastrointestinal upset.

This depends on the timing and your personal preference. Solid food requires more time to digest. Closer to the race, liquid carbs like sports drinks or gels can be beneficial for a faster energy boost, as they are rapidly absorbed.

It is best to minimize fat intake in the final 2-4 hours before a race because it slows digestion and can lead to a heavy, sluggish feeling. However, healthy fats are an important part of your diet during training.