Should I have a protein bar before a race? Pros, cons, and better fueling strategies

December 15, 2025 •

3 min read

Approximately 30-80% of endurance athletes experience gastrointestinal distress during races, making pre-race nutrition choices critical. When planning your race day fuel, you might wonder: 'Should I have a protein bar before a race?' This article explores why most experts advise against it, the potential risks involved, and superior, easily digestible alternatives to fuel your performance.

Quick Summary

Discover the optimal timing and composition of pre-race fuel. Learn why high-protein bars may cause GI issues and explore superior, easily digestible alternatives for peak race day performance.

Key Points

Prioritize Carbohydrates: Focus on easily digestible carbohydrates, not protein, in the hours before a race to ensure quick energy and prevent digestive issues.
Timing Is Crucial: Eat your main carb-heavy meal 2-4 hours before the race and a small, simple carb snack 30-60 minutes before for an energy top-up.
Avoid GI Distress: High protein, fat, fiber, and sugar alcohols found in many protein bars can lead to uncomfortable bloating, gas, and cramping during your race.
Test During Training: Never introduce a new food, including a protein bar, on race day. Practice your entire fueling strategy during long training runs to know what works for your body.
Reserve Protein for Recovery: The best time for a protein bar is after your race to aid in muscle repair and replenish depleted glycogen stores, not before.
Choose Better Alternatives: Opt for energy gels, chews, dates, rice cakes, or a banana pre-race for safer and more effective fueling.

The Core Conflict: Why Protein Before a Race Is Risky

While protein is essential for muscle repair, it's not the ideal fuel before an endurance race; carbohydrates are preferred for efficient energy. Consuming a protein bar too close to a race can lead to digestive discomfort.

The Slow Digestion Problem

Protein and fat digest slower than carbohydrates. During exercise, blood flow shifts from the digestive system to muscles, making it difficult to process a dense protein bar. This can result in bloating, cramping, and a heavy feeling.

The High Fiber and Sugar Alcohol Issue

Many protein bars contain high fiber and sugar alcohols, which can cause significant GI distress like gas, bloating, and diarrhea before a race. Sugar alcohols are particularly known for their laxative effect. Avoiding these is crucial for race day.

Optimal Pre-Race Fueling Strategy: Prioritizing Carbohydrates

The best pre-race strategy focuses on easily digestible carbohydrates to replenish glycogen stores through timed meals and snacks.

The 2-4 Hour Window: The Main Meal

Consume your last significant meal 2 to 4 hours before the race. It should be high in carbohydrates and low in protein and fat for easy digestion. Examples include white rice with lean meat or a bagel with jam.

The 30-60 Minute Window: The Final Top-Up

Have a small, easily digestible snack 30-60 minutes before the start for a quick energy boost. Focus on simple sugars like those found in half an energy bar, dates, or a gel.

Comparison Table: Protein Bars vs. Energy Bars for Pre-Race

This table highlights the differences between protein and energy bars for pre-race fueling.


Feature	Protein Bar	Energy Bar (Carbohydrate-Focused)
Primary Nutrient	High protein (often 15-25g+)	High carbohydrate (often 30-50g+)
Digestion Speed	Slow due to high protein/fat	Fast due to higher simple carb content
Best Use	Post-workout recovery or daily snack	Pre-workout/pre-race fuel
GI Distress Risk	Higher due to fiber/sugar alcohols	Lower if low in fiber and fat
Ideal Timing	Any time other than immediately pre-race	30-60 minutes before race for quick energy
Race Performance	Poor; can cause stomach issues	Optimal; provides quick, accessible energy

Better Pre-Race Alternatives to a Standard Protein Bar

Choose these alternatives for effective pre-race fueling without GI risks:

Energy Gels: Provide concentrated, quickly absorbed simple carbohydrates, ideal for close to race time or during the event.
Dates: A natural, digestible source of carbohydrates for a last-minute energy boost.
Rice Cakes: Light, carb-heavy, and easy on the stomach.
Toast with Jam: Offers simple, digestible carbohydrates.
Banana: Provides easily digestible carbs and electrolytes.
Pretzels: Quick carbs and help with sodium replenishment.

Making the Final Decision: When a Protein Bar Might Work

A protein bar might be acceptable for a very short, low-intensity workout if tested beforehand and if it has a high carb-to-protein ratio and low fiber. However, for any significant race, prioritize pure carbohydrate sources. Always practice your nutrition plan during training.

Conclusion: Fuel Smart, Race Strong

Generally, having a protein bar before a race is not recommended due to the risk of digestive issues. Focus on easily digestible carbohydrates in the hours before and a simple carb snack 30-60 minutes prior for optimal performance. Test your strategy during training and stick to what works for you on race day. For more on race-week nutrition, see this guide on Ironman.com.

Frequently Asked Questions

The main reason is that protein and fat take longer to digest than carbohydrates, and your body diverts blood flow from your digestive system to your muscles during intense exercise. This can cause gastrointestinal issues like bloating and cramping.

Sugar alcohols, such as maltitol and sorbitol, are low-calorie sweeteners used in many protein bars. They are poorly digested and can cause significant GI distress, including gas and diarrhea, especially before or during a race.

The best time to have a protein bar is after a race or intense workout. This is when your body needs protein to repair muscles and start the recovery process.

No, you should not. Carb loading involves increasing your intake of carbohydrates in the days leading up to a race to maximize glycogen stores. Protein bars are not an efficient source for this purpose and can displace the carbohydrate-rich foods you need.

A small, simple carbohydrate-based snack that is easy to digest is best. Options include an energy gel, a handful of dates, or a small banana.

Yes, a low-fiber, carbohydrate-focused energy bar is a far better choice, especially if you have tested it during training. Look for one with easily digestible carbohydrates and a lower protein and fat content.

It should be a carbohydrate-rich meal that is low in fat and fiber. Examples include low-fiber oatmeal, a bagel with jam, or white rice.