Nutrition and Supplementation for Runners:

How to Optimize Performance.

 

by Simone Bisello

 

Whether it's a 5K or a marathon, running isn’t just about trained muscles. To support performance, avoid energy crashes, and reach the finish line in the best possible shape, you need a well-fueled engine — and that fuel is nutrition. Whether you're preparing for a short race or a long-distance event, managing your energy is what makes the difference between finishing strong and dropping out. Nutrition is an essential part of your race strategy.

Here’s how to properly fuel performance — from the first to the final kilometer.

Why Nutrition Is Key in Running

 

In shorter races (5 or 10 km), you run at high intensity, and performance is determined in a relatively short time. Even if the total energy expenditure isn’t very high, nutrition still plays an important role: starting with the right energy reserves can make the difference between maintaining a steady pace and fading before the finish line.
In longer races, such as a half marathon or marathon, the overall energy demand is much greater. Without a solid energy and hydration strategy, there’s a real risk of not finishing the race.

In both cases, the principle remains the same: your body needs strategic fueling. And that depends on a key reserve for runners - glycogen.

Glycogen: The Fuel Tank to Fill Before the Start

 

Glycogen is the storage form of carbohydrates in the body and the primary fuel for high-intensity running. It’s stored in the muscles (approx. 300–500 g) and the liver (approx. 80–100 g), and it can support around 90–120 minutes of intense activity before running low.

• In short races (5K or 10K), glycogen is the main energy source due to the brief duration and high intensity.
• In longer races like half marathons or marathons, effort lasts well beyond 90 minutes. The body also uses fat reserves, but glycogen is still essential to maintain pace during higher-intensity moments.

Making sure you have optimal glycogen levels through proper carbohydrate intake is the foundation for supporting and optimizing performance.

Optimizing Glycogen Stores Before the Race

 

Traditional protocols that recommended high carbohydrate loading in the days before a race are now outdated. New scientific evidence favors a more moderate approach. In the week leading up to the race, training load decreases — so there’s no need for a massive increase in carbs.

In the 2–3 days before the event, a moderate increase in carbohydrate intake is enough. Focus on easy-to-digest, low-fiber and low-fat foods such as white bread, rice, pasta, potatoes, honey, jam, and fruit juices. It’s also advisable to maintain a moderate intake of lean proteins like chicken breast, bresaola, lean fish, yogurt, or cottage cheese.

This approach helps maximize glycogen reserves without overloading the body, allowing you to approach the race with optimal energy and performance.

How Many Carbohydrates Should You Eat before the race?

 

A good guideline is between 5 and 10 grams of net carbohydrates* per kilogram of body weight per day, for the 2–3 days leading up to the race. For example, a 70 kg athlete should consume between 350 and 700 g of carbs per day, spread over multiple meals and snacks. This is a broad range, and should be adapted based on race length, training level, and individual needs.

Important: This strategy should always be tested during training — never introduce it for the first time on race day.

*Refers to actual carbohydrate content (not total food weight).

Pre-Race Breakfast: The Final Fuel Top-Up

 

Race-day breakfast is your last chance to refuel, particularly to restore liver glycogen, which gets depleted overnight. These reserves are crucial for maintaining blood sugar levels during the race.

Scientific recommendations suggest 2–4 g of carbohydrates per kilogram of body weight. The earlier your breakfast is before the start, the more you can eat. Focus on low-fat, low-fiber, easily digestible carbs such as white bread, jam, honey, cereal, or porridge. You may also include a portion of lean protein to support muscle tissue.

In the hour before the race, a "pre-start snack" can be helpful: 20–30 g of fast-digesting carbs, typically from supplements.

In-Race Carbohydrate Supplementation

 

For races under one hour, carbohydrate intake during the event is usually not necessary — as long as glycogen stores were filled properly in the days before.

When the race exceeds 60 minutes, it’s recommended to take in 30–60 grams of carbohydrates, ideally around the halfway point. The best sources are fast-absorbing carbs such as maltodextrins, glucose, and fructose — found in gels or gummies. Products with a 2:1 glucose-to-fructose ratio tend to have better gastric tolerance, which is crucial for runners.

For races lasting over two hours, carbohydrate intake should be planned for the entire duration. Providing a steady energy supply is key to sustaining performance and meeting energy demands.

How Much to Take During Long-Distance Races?

 

In running, total energy expenditure depends mostly on duration, not pace. A slower runner may burn less energy per minute but do so for longer, resulting in similar total energy needs. This means carbohydrate supplementation should be tailored to expected race duration.

Scientific studies have shown that even intakes over 90 g/hour can improve long-distance performance. However, too much at once may cause gastrointestinal issues and reduce performance. The best strategy is to start with full glycogen reserves and consume 30–60 g of carbohydrates per hour, regularly and from the start of the race. As mentioned, the 2:1 ratio of maltodextrins to fructose offers benefits, especially in terms of tolerance.

Whatever your strategy, never improvise on race day. Always test both dosage and products during training.

Hydration in Running

 

Starting hydrated is essential — and hydration begins days before the race. A simple check? Look at your urine color: light = hydrated; dark = drink more. On race morning (or before a key workout), drink around 500 ml of an electrolyte drink with sodium. Sodium helps retain fluids, improving hydration.

In short races, you typically don’t need to drink while running. In longer or hot/humid events, regular hydration at aid stations is vital to maintain performance and prevent dehydration.

Caffeine: A Mental and Physical Boost

 

Caffeine can enhance performance by improving focus, reducing perceived exertion, and increasing fat oxidation. The effective dose is generally 3–6 mg per kg of body weight, though individual response and timing vary.

General guidelines:

• For short races: take caffeine before the start.
• For long races: consider both pre-race and mid-race intake.

Always test caffeine use during training. Do not exceed 400 mg per day to avoid side effects.

Post-Run Recovery: Replenish and Rebuild

 

Post-run recovery is essential to restore energy reserves and support muscle repair. Immediately after running, consume fast-digesting carbohydrates to quickly replenish glycogen stores. Add a source of high-quality protein, such as whey, to promote muscle repair — especially important after long or intense runs.

Recovery can also be supported by antioxidants and anti-inflammatory compounds like tart cherry juice (rich in polyphenols) and omega-3s, which help reduce oxidative stress from intense exercise.

Summary Glycogen loading: decrease training and moderately increase carbs 2–3 days before the race. Pre-race breakfast: aim for 2–4 g/kg of carbs, low in fat and fiber. Always test in training. In-race fueling: use a personalized approach. Short races may not need it; long ones do. Hydration: start hydrated. Monitor urine color. Use electrolyte drinks with sodium. Hydrate during long/hot races. Recovery: within 30 minutes of finishing, take in simple carbs + whey protein to support recovery.

Running rewards those who train smart and fuel strategically. Because every kilometer counts - and energy makes the difference.

 

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IMPORTANT NOTICE: the information provided is for informational purposes only and does not replace the advice of your physician or a qualified healthcare professional. The content is intended for healthy individuals: any dietary regimen or physical activity must be supervised by a qualified professional, as required by Italian law. Enervit S.p.A. assumes no responsibility, as the information is purely educational. Anyone wishing to begin a nutritional or physical activity program should first consult with their trusted specialist.