Can I eat fries before a marathon? The definitive nutrition guide

Running a marathon is a monumental effort, and fueling your body correctly is just as crucial as your training. A common question among runners is: can I eat fries before a marathon? The short answer is that high-fat, fried foods like french fries should generally be avoided right before a race to prevent gastrointestinal issues and sluggishness.

Quick Summary

This guide explains why fried foods are not ideal before a marathon and details proper pre-race nutrition strategies, including what to eat for carb-loading and on race day morning. It also covers common foods to avoid to prevent digestive distress and ensure you perform your best.

Key Points

• Avoid fried foods: High-fat, fried foods like french fries are difficult to digest and should not be consumed before a marathon.

• Choose wisely: Baked or mashed potatoes are a great alternative, providing easy-to-digest carbs and valuable electrolytes like potassium.

• Plan ahead: Proper pre-race fueling is a multi-day process involving carb-loading and testing familiar foods during training.

• Minimize fiber and fat: Reduce intake of high-fiber and high-fat foods in the 24 hours leading up to the race to avoid GI distress.

• Eat familiar foods: Never introduce new foods on race day. Stick to what your body is used to and what you've practiced during training.

• Prioritize carbs: The bulk of your pre-race meals should be easily digestible carbohydrates to maximize glycogen stores.

• Timing is key: Eat your final big meal the night before, and a smaller, carb-focused breakfast 2-4 hours before the race.

The Problem with Fried Foods Before a Marathon

While delicious, french fries are considered a high-fat, fried food, which makes them a poor choice for pre-race fueling. The primary goal of marathon nutrition is to top off glycogen stores with easily digestible carbohydrates. Fried foods work against this by slowing down the digestive process and leaving you feeling heavy and lethargic when you need to feel light and energetic.

Delayed Digestion

High-fat foods take significantly longer for your body to digest compared to carbohydrates and protein. When you run, blood is diverted from your digestive system to your working muscles. If your stomach is still busy processing a greasy meal, this can lead to uncomfortable gastrointestinal (GI) distress, including cramps, bloating, and nausea.

Risk of Bloating and Cramping

The combination of fats and potentially high fiber content in some fries can increase the risk of bloating and gas. During a marathon, this discomfort can be magnified, leading to a miserable race experience or even forcing you to stop. A runner's focus should be on their pace and effort, not on an upset stomach.

Suboptimal Energy Source

While potatoes themselves are an excellent source of complex carbohydrates, the frying process adds a large amount of saturated and trans fats. These fats are not an efficient or fast-acting fuel source for high-intensity, long-duration exercise like a marathon. For peak performance, your body needs quick-access, high-glycemic carbohydrates to fuel your muscles.

The Smart Alternative: Baked Potatoes

Instead of fried fries, a baked or mashed potato can be an excellent pre-marathon meal. Potatoes are a nutrient-dense whole-food carbohydrate that is gentle on the stomach and provides sustained energy. They are also packed with potassium, an essential electrolyte that aids in muscle function and can help prevent cramps.

Baked Potato vs. French Fries

Feature	Baked Potato	French Fries
Carbohydrate Source	Complex, slow-release carbohydrates	Complex carbs, but obscured by frying
Fat Content	Very low	Very high, especially in saturated and trans fats
Digestion Speed	Easily and quickly digested	Slows down digestion significantly
Nutrient Density	Rich in potassium, iron, and magnesium	Lower due to cooking method
Risk of GI Distress	Low risk, gentle on the stomach	High risk of bloating, cramping, and nausea

Proper Pre-Marathon Fueling Strategy

Proper nutrition before a marathon is a multi-day process that requires careful planning and testing during training.

The Days Leading Up to the Race (Carb-Loading)

In the 2-3 days before the marathon, the focus shifts to carb-loading. This means increasing your carbohydrate intake to about 70-80% of your total calories to maximize your muscle glycogen stores. Choose nutrient-dense, lower-fiber carbs that you know sit well with your stomach.

Good carb-loading options:

• Pasta with a light, non-spicy sauce
• White rice or peeled potatoes
• Oatmeal or low-fiber cereals
• Bagels and white bread
• Fruits like bananas or applesauce

The Night Before the Race

The final dinner should be a familiar, carbohydrate-heavy meal with moderate protein and minimal fat and fiber. This provides a final top-off of your glycogen stores without taxing your digestive system overnight. Avoid anything new, spicy, or heavy.

Race Morning Breakfast

Eat a small, easy-to-digest breakfast 2-4 hours before the race. This allows for sufficient digestion time and prevents a mid-race energy crash. Stick to foods you've tested during your training runs.

Race morning options:

• Bagel with a small amount of peanut butter or honey
• Oatmeal with a banana
• Toast with jam
• Energy gels or chews 15-20 minutes before the start

What to Avoid in the 24 Hours Before a Marathon

To ensure a successful race, steer clear of foods and habits that can sabotage your performance:

• Fried and Greasy Foods: As established, these slow digestion and can cause GI distress.
• High-Fiber Foods: While healthy, too much fiber can lead to bloating and unwanted bathroom breaks. Avoid large quantities of beans, legumes, and cruciferous vegetables.
• Spicy Foods: These can irritate your stomach lining and cause heartburn.
• Excessive Protein or Fat: Both take longer to digest and can leave you feeling sluggish.
• Alcohol: It's a diuretic that can lead to dehydration and disrupt sleep, both detrimental to race day performance.
• Dairy (if intolerant): If you are sensitive to dairy, avoid it to prevent gastrointestinal problems.
• Trying New Foods: Never experiment with new foods or supplements on race day. Stick to what you've practiced.

Conclusion

While the potato itself is a marathon-friendly food, the frying process makes french fries a poor choice for pre-race fueling. The high fat content and slow digestion can lead to significant gastrointestinal distress and leave you feeling sluggish. Instead, focus on a well-planned nutrition strategy throughout your taper, prioritizing easily digestible, high-carbohydrate meals and snacks. Save the fries for a well-deserved post-marathon celebration, where they can help replenish sodium and carbs as part of your recovery.

References

• STYRKR. (2025). What to Eat Before a Marathon, the Go-to Guide for Runners. Retrieved from https://styrkr.com/blogs/training-and-nutrition-hub/what-to-eat-before-a-marathon
• BBC Good Food. (2024). 10 foods that runners should avoid. Retrieved from https://www.bbcgoodfood.com/health/fitness/10-foods-that-runners-should-avoid
• Runzy. (2022). Runner's Diet: 6 Foods to Avoid. Retrieved from https://runzy.com/blog/runners-diet-6-foods-to-avoid/
• Peloton. (2024). What to Eat the Night Before a Race. Retrieved from https://www.onepeloton.com/blog/what-to-eat-the-night-before-a-race
• Peloton. (2025). What to Eat Before a Marathon: The Ultimate Guide. Retrieved from https://www.onepeloton.com/blog/what-to-eat-before-a-marathon
• STYRKR. (2025). What to Eat Before a Marathon, the Go-to Guide for Runners. Retrieved from https://styrkr.com/blogs/training-and-nutrition-hub/what-to-eat-before-a-marathon
• Verywell Fit. (2024). What to Eat Before a Run: Your Guide to a Runner's Diet. Retrieved from https://www.verywellfit.com/should-i-eat-before-a-run-2911547
• My BEST Runs. (2025). Potatoes: The Ideal Pre-Marathon Fuel? Retrieved from https://mybestruns.com/running-news.php/13651
• apre.org. Potatoes and Physical Performance. Retrieved from https://apre.org/nutrition-science/healthy-lifestyles/potatoes-and-physical-performance/
• Spud Smart. (2025). Potatoes Powering Canada's Marathon Momentum. Retrieved from https://spudsmart.com/potatoes-powering-canadas-marathon-momentum/
• STYRKR. (2025). What to Eat Before a Marathon, the Go-to Guide for Runners. Retrieved from https://styrkr.com/blogs/training-and-nutrition-hub/what-to-eat-before-a-marathon
• Peloton. (2025). What to Eat Before a Marathon: The Ultimate Guide. Retrieved from https://www.onepeloton.com/blog/what-to-eat-before-a-marathon
• Runna. (2024). What to eat before running: 25 foods and drinks to fuel your runs. Retrieved from https://www.runna.com/blog/what-to-eat-before-running-25-foods-and-drinks-to-fuel-your-runs
• Summa Health. (2023). What to Eat Before a Marathon. Retrieved from https://www.summahealth.org/flourish/entries/2023/05/what-to-eat-before-a-marathon

Frequently Asked Questions

Why are french fries bad for marathon runners before a race?

French fries are high in fat, which significantly slows down digestion. Before a marathon, your body needs fast-acting, easily digestible fuel. The fats in fries can lead to sluggishness, bloating, and stomach cramps as your body diverts blood flow to working muscles during the race.

Can I eat a regular baked potato before a marathon?

Yes, a regular baked or mashed potato is a much better choice than fries. Potatoes are an excellent source of complex carbohydrates and potassium, are gentle on the stomach, and provide sustained energy without the added fat that causes digestive issues.

What is the best way to carb-load before a marathon?

Carb-loading is a 2-3 day process of increasing carbohydrate intake to 70-80% of your total calories. Choose low-fiber, high-carb options like pasta, rice, and potatoes. Test your carb-loading strategy during long training runs to find what works best for you.

What should I eat for dinner the night before a marathon?

The night before, aim for a familiar, carbohydrate-heavy meal with moderate protein and low fat and fiber. Good examples include pasta with a light sauce or a large baked potato with grated cheese. Avoid anything spicy or new.

How long before the marathon should I eat breakfast?

It's best to eat your pre-race breakfast 2-4 hours before the marathon starts. This allows ample time for digestion, ensuring you're not running on a full stomach. Stick to simple, high-carb foods you've tested in training.

Should I eat salty foods before a marathon?

A moderate amount of salt is beneficial before and during a marathon to replace electrolytes lost through sweat, especially sodium. However, this should come from planned, controlled sources like salted pretzels or electrolyte drinks, not greasy, fried foods.

Can I have a small amount of fried food during my training?

While it's not ideal for optimal performance, a small amount of fried food is fine during regular training, especially on easy or rest days. The key is to avoid it before high-intensity runs or races to prevent digestive discomfort.