What to Avoid When Carb Loading: A Guide to Optimizing Your Race Day Fuel

October 2, 2025 •

2 min read

Endurance athletes who carb-load correctly can increase their glycogen stores by 30% or more, significantly boosting performance. This strategy involves carefully selecting the right foods and, just as importantly, knowing what to avoid when carb loading to prevent stomach upset on race day.

Quick Summary

An effective carb-loading strategy hinges on avoiding foods that can hinder glycogen storage or cause gastrointestinal distress. Key culprits include high-fiber foods, excessive fat and protein, alcohol, and unfamiliar items, all of which can compromise performance.

Key Points

Limit Fiber: Avoid high-fiber foods like whole grains, beans, and certain raw vegetables in the final 24-48 hours to prevent stomach issues.
Reduce Fat and Protein: Excess fat and protein slow digestion and take up valuable space for carbs, so favor low-fat sources and moderate protein.
Skip Alcohol: Alcohol interferes with hydration and proper glycogen storage, negatively impacting race performance.
Steer Clear of Unfamiliar Foods: Never experiment with new foods or recipes in the days before a race to avoid unexpected gastrointestinal problems.
Hydrate Strategically: Drink plenty of fluids, including water and electrolyte drinks, but avoid overly sugary or carbonated drinks that can cause GI distress.
Don't Fear Carbohydrates: Embrace low-fiber, easily digestible carb sources, including refined options like white pasta and rice, for efficient glycogen storage.

Carb loading is a strategic fueling protocol designed to maximize the storage of glycogen—the body's primary energy source during prolonged, high-intensity exercise. Typically reserved for endurance events lasting over 90 minutes, such as marathons, triathlons, and long-distance cycling races, the goal is to fully stock your energy reserves. While focusing on high-carbohydrate foods is essential, knowing what to leave out of your diet in the final 24 to 72 hours can be the difference between a personal best and a miserable race day.

High-Fiber Foods

In the final days before an endurance event, a high-fiber diet can lead to digestive problems like gas and bloating. Fiber is indigestible, and large amounts can cause discomfort, especially with increased food volume. Switching to lower-fiber, refined alternatives is recommended.

High-Fiber Foods to Limit

Whole grains (brown rice, whole wheat pasta)
Legumes (beans, lentils)
Cruciferous vegetables (broccoli, cauliflower)
High-fiber cereals
Certain fruits (raspberries)

Excessive Fat and Protein

Carb loading focuses on increasing carbohydrate intake, not total calories. High-fat foods are calorie-dense and can make it difficult to consume enough carbs while also slowing digestion. Similarly, protein is digested more slowly than carbohydrates and excessive amounts can displace carbs.

Examples of High-Fat and Protein Foods to Reduce

Fried foods
Creamy sauces
Rich desserts
Fatty cuts of meat

Alcohol and Certain Sugary Foods

Alcohol is a diuretic that can hinder hydration and glycogen storage, negatively impacting performance. Excessive consumption of highly processed, sugary foods can lead to energy crashes and don't provide the same quality fuel as complex carbohydrates.

What to Avoid in This Category

Alcoholic beverages
Excessive processed sweets
High-fructose sources like some fruit juices

New and Unfamiliar Foods

Introducing new foods in the days before a race is risky. Stick to foods you've eaten before to avoid unexpected digestive issues.

Avoiding Carb-Loading Mistakes: A Quick Comparison

This table highlights the differences between common carb-loading errors and the correct approach.


Pitfall (What to Avoid)	Correct Approach (What to Choose)
High-Fiber Foods: Wholemeal bread, brown rice, beans, leafy greens.	Low-Fiber Carbs: White bread, white rice, peeled potatoes, pasta.
High-Fat Foods: Fried foods, creamy sauces, rich pastries.	Low-Fat Foods: Baked potatoes, simple tomato-based sauces, lean protein.
Excessive Protein: Large steaks or high-protein meals.	Moderate Lean Protein: Small portions of chicken breast or white fish.
Alcohol: All beer, wine, and spirits.	Hydrating Fluids: Water, electrolyte drinks, sports drinks.
New Foods: Experimenting with a new restaurant or recipe.	Familiar Foods: Sticking to your practiced fueling plan.

Final Thoughts on Strategic Avoidance

Avoiding high-fiber, high-fat foods, limiting protein, and abstaining from alcohol helps optimize glycogen storage and minimizes GI issues. Practice your race week nutrition during training. Consulting a sports dietitian can provide a personalized plan.

Frequently Asked Questions

High-fiber foods can cause gas, bloating, and general gastrointestinal distress when consumed in large quantities, which can negatively affect your performance and comfort during an endurance event.

It is best to avoid high-fat options like pizza and creamy sauces. The high fat content slows digestion and can lead to bloating, displacing the space needed for carbohydrates.

No, alcohol should be avoided during carb loading. It is a diuretic that promotes dehydration and can interfere with the efficient storage of glycogen in your muscles.

Yes, during the carb-loading phase, low-fiber carbs such as white bread, white rice, and plain pasta are preferred. They are easier to digest and help maximize glycogen stores without causing GI issues.

While some fat is necessary, you should reduce your overall fat intake during the carb-loading period. High-fat foods are calorie-dense and can make it difficult to hit your high carbohydrate targets.

Sticking to familiar foods prevents unexpected digestive issues or adverse reactions on race day. Your body knows how to process foods you regularly eat, so you eliminate unnecessary risk.

Focus on consuming plenty of water, and consider incorporating electrolyte or carbohydrate drinks to aid hydration and meet your carb targets, especially if you find it hard to eat enough solid food.