Fueling for the Long Haul: What to Eat Before a 50K Run

November 21, 2025 •

3 min read

According to sports nutritionists, the right pre-race nutrition can improve endurance performance by 2-3% in events lasting over 90 minutes. This makes understanding what to eat before a 50K run a critical component of your training plan, far beyond just logging the miles.

Quick Summary

This guide outlines the optimal pre-race nutrition strategy for a 50K ultramarathon, focusing on strategic carbohydrate loading, meal timing, and appropriate food choices to ensure you are properly fueled and hydrated. Proper pre-run meals and snacks, along with hydration, are crucial for a successful race.

Key Points

Carb-load strategically: Spend 2-3 days before the race increasing carbohydrate intake to top off glycogen stores, not overstuff yourself.
Eat 2-4 hours before: Have a carbohydrate-rich, low-fiber, low-fat meal 2 to 4 hours pre-race to allow for proper digestion.
Embrace simple carbs on race morning: Stick to easily digestible, low-fiber options like oatmeal, bananas, or a bagel.
Practice your fuel strategy: Test all race-day foods, gels, and drinks during long training runs to avoid race-day surprises.
Consider hydration and electrolytes: Don't neglect proper hydration in the days and hours leading up to the run; consider electrolyte drinks.
Avoid new foods: Never introduce new foods or products on race day to prevent potential stomach issues.

Why Pre-Race Nutrition Is Crucial for Ultra Runners

For endurance athletes tackling a 50K, proper nutrition is as vital as your physical training. A 50K ultramarathon demands sustained energy over many hours, and without a well-practiced fueling strategy, you risk hitting "the wall"—a complete depletion of muscle glycogen stores. While you cannot store enough fuel to complete the entire race without taking on calories during the run, starting with fully saturated glycogen reserves significantly improves performance and delays fatigue.

The Taper Week: Strategic Carbohydrate Loading

Your race day nutrition begins several days before the event, during your taper period. The goal is to build up your body's glycogen stores, not to eat until you are uncomfortably full. Instead of stuffing yourself, slightly increase the percentage of carbohydrates in your diet while reducing fat and fiber intake to avoid stomach issues. Aim for 7-10 grams of carbs per kilogram of body weight per day in the 2-3 days leading up to the race.

Recommended Carb-Loading Foods

Complex Carbs: Whole-grain bread, pasta, rice, oatmeal, and potatoes provide sustained energy.
Refined Carbs (closer to race): White bread, bagels, and low-fiber cereals are excellent for topping off stores without digestive distress.
Hydration: Alongside your meals, consistently drink fluids. Consider adding electrolytes to aid fluid retention.

Race Morning: The Final Fueling

The morning of the 50K, you need a meal that is primarily carbohydrates, low in fiber, fat, and protein to ensure quick digestion. Aim to eat 2-4 hours before the race starts to give your stomach ample time to process the food. For those with early start times, a smaller, quicker-digesting snack 30-60 minutes before the gun goes off is a better option.

Sample Race Morning Meals

Porridge or oatmeal with a banana and a drizzle of honey.
Toast or a bagel with a thin layer of peanut butter and jam.
A smoothie with fruit, a scoop of protein powder, and low-fat yogurt.

What to Eat During a 50K

Even with optimal pre-race fueling, you will need to take in calories during the race. Aim for 200-250 calories per hour, primarily from carbohydrates, ingested in small, frequent amounts (every 15-20 minutes). Experiment during training with a variety of fuel sources to prevent palate fatigue and gastrointestinal issues.

Comparison Table: Fueling Options for a 50K Run


Fuel Type	Pros	Cons	Best Used
Energy Gels	Quick, concentrated carbs; easy to carry.	Can cause stomach upset; sticky texture; must be chased with water.	During high-intensity periods; for quick energy boosts.
Chews/Blocks	Portable; easier to eat than gels for some.	Requires chewing; can be harder to digest in later stages.	Steady, frequent intake throughout the race.
Real Food (e.g., Bananas, Potatoes)	Less risk of stomach upset; provides wider range of nutrients.	Messier to carry; slower digestion; may require aid station support.	During slower, flatter sections or walking breaks.
Sports Drinks	Hydrates and provides carbs simultaneously.	Can be too sugary for some; potential for GI issues if over-consumed.	Steady hydration and energy, especially in warmer conditions.

Practicing Your Strategy

The golden rule of ultra-running nutrition is "nothing new on race day". Your training runs are the time to test different foods, timings, and hydration strategies. The goal is to discover what your unique gastrointestinal system can tolerate under race conditions. Your race-day strategy should be a well-rehearsed plan, not an experiment. This includes practicing with the specific gels, bars, or real foods you intend to use and understanding your fluid and electrolyte needs.

Conclusion: Your Ultra-Running Success Starts on Your Plate

Ultimately, conquering a 50K is a holistic endeavor where physical training, mental fortitude, and a well-executed nutrition plan converge. By strategically carb-loading in the days prior, consuming a light, carb-heavy meal on race morning, and practicing your in-race fueling, you set yourself up for a powerful and resilient performance. Don't underestimate the power of your plate—it's the foundation of your long-distance success. For additional resources on training and nutrition, consider exploring the guides on REI Expert Advice.

Frequently Asked Questions

You should begin strategic carb-loading 2 to 3 days before your 50K event, focusing on increasing your carbohydrate percentage while slightly decreasing fat and fiber.

A good race morning breakfast is high in carbs and low in fiber, fat, and protein. Examples include oatmeal with a banana, a bagel with jam, or a fruit smoothie, consumed 2-4 hours before the race.

Avoid high-fat foods, high-fiber foods, and spicy meals before your race, as these can be difficult to digest and cause gastrointestinal distress during your run.

Ensure you are consistently hydrating in the days leading up to the race. On race morning, drink fluids until your urine is pale yellow. Consider electrolyte drinks to aid in fluid retention.

Energy gels and chews are highly effective for providing quick, concentrated carbohydrates, which are necessary for maintaining energy levels during a 50K. They should be practiced during training runs to ensure tolerance.

If you have trouble with solid food on race morning, opt for a smaller, easily digestible snack 30-60 minutes before the start, such as a banana, or a liquid option like a sports drink or smoothie.

If you are a regular caffeine consumer, you can have a moderate amount on race morning. However, if you are not accustomed to it, it is best to avoid it to prevent dehydration or jitters.