Marathon Fueling: Energy Gels, Timing, and Individual Strategy

How Many Gels for a Marathon?

For most marathon runners, a general guideline is to consume 30-60 grams of carbohydrates per hour, which typically translates to 1 to 2 energy gels every 30-45 minutes after the first hour, depending on the gel's carbohydrate content and individual needs.

The Science Behind Carbohydrate Needs in a Marathon

Marathon running is an endurance event that primarily relies on carbohydrates as its primary fuel source, especially at moderate to high intensities. Our bodies store carbohydrates as glycogen in the muscles and liver. These glycogen stores are finite and typically last for about 90-120 minutes of continuous exercise.

• Glycogen Depletion: Once glycogen stores are significantly depleted, the body must rely more heavily on fat for fuel. While fat stores are abundant, converting fat into energy is a slower process, leading to a noticeable decrease in pace and perceived effort, often referred to as "hitting the wall" or "bonking."
• Exogenous Carbohydrates: To delay glycogen depletion and maintain performance, supplementing with exogenous (external) carbohydrates during the race is crucial. These carbohydrates are absorbed from the digestive system into the bloodstream, providing a continuous supply of glucose for working muscles.
• Carbohydrate Oxidation Limits: The body's ability to absorb and utilize ingested carbohydrates is limited. For most individuals, the maximum absorption rate for a single type of carbohydrate (like glucose or maltodextrin) is around 60 grams per hour. However, by using a combination of carbohydrates (e.g., glucose and fructose), which utilize different transporters in the gut, absorption rates can be increased to 90 grams per hour or even higher in highly trained athletes.

General Recommendations for Marathon Fueling

Current sports nutrition guidelines recommend a carbohydrate intake ranging from 30 to 60 grams per hour for endurance events lasting over 2.5 hours. Highly trained athletes or those aiming for faster times may benefit from up to 90 grams of carbohydrates per hour, particularly if they have practiced this in training and their gut is adapted.

• Start Early: Begin consuming carbohydrates within the first 45-60 minutes of the race, before significant glycogen depletion occurs. This proactive approach helps maintain blood glucose levels and conserve existing glycogen stores.
• Consistent Intake: Aim for a steady intake rather than large boluses. Small, frequent doses are generally better tolerated and provide a more consistent energy supply.
• Carbohydrate Types: Most energy gels contain rapidly absorbed carbohydrates like maltodextrin and/or fructose. Maltodextrin is a polymer of glucose, quickly broken down and absorbed. Fructose uses a different transporter, allowing for higher total absorption when combined with glucose.

How Many Gels Translate to Grams of Carbohydrate?

The carbohydrate content of energy gels can vary, but most standard gels provide between 20 and 25 grams of carbohydrates per serving. Some larger or "high-carb" gels may offer 30-45 grams.

To calculate your gel needs:

• If aiming for 30g carbs/hour: You'll need approximately 1 standard gel per hour.
• If aiming for 60g carbs/hour: You'll need approximately 2 standard gels per hour, or one high-carb gel.
• If aiming for 90g carbs/hour: You'll need approximately 3-4 standard gels per hour, or a combination of high-carb gels and other sources.

For a typical 4-hour marathon, this could mean:

• Minimum (30g/hr): 1 gel after 45-60 minutes, then 1 gel every hour. Total: Approximately 3-4 gels.
• Moderate (60g/hr): 1 gel every 30 minutes, or 2 gels every hour. Total: Approximately 7-8 gels.
• Aggressive (90g/hr): 1 gel every 20 minutes, or 3-4 gels every hour. Total: Approximately 10-12+ gels.

Remember to factor in any carbohydrates consumed from sports drinks or other fuel sources.

Factors Influencing Your Individual Gel Strategy

While general guidelines exist, your optimal gel strategy is highly individual and depends on several factors:

• Body Weight and Size: Larger individuals generally have greater energy demands and may require more carbohydrates.
• Pace and Intensity: Running at a faster pace burns carbohydrates at a higher rate, necessitating increased intake. Slower paces might allow for slightly less aggressive fueling.
• Training Status and Adaptation: Highly trained athletes often have improved metabolic efficiency and may be better at utilizing fat for fuel, but they also push harder, increasing overall caloric demand. Crucially, "gut training" (practicing fueling during long runs) improves the body's ability to absorb and tolerate carbohydrates.
• Pre-Race Fueling: Adequate carbohydrate loading in the days leading up to the race ensures maximal glycogen stores, providing a buffer before you need to rely heavily on gels.
• Race Duration: Longer projected race times will naturally require more total gels.
• Environmental Conditions: Hot and humid conditions increase sweat rates and can impact digestion, sometimes requiring a slightly modified fueling plan.
• Other Fuel Sources: If you are also consuming sports drinks (which contain carbohydrates) or other solid foods (e.g., chews, bars), adjust your gel intake accordingly to avoid exceeding your hourly carbohydrate target.

Practical Application: Developing Your Gel Strategy

The most critical step in determining your personal gel strategy is to practice, practice, practice during your long training runs.

• Practice in Training: Never try a new gel or fueling strategy on race day. Use your long runs to experiment with different brands, flavors, and timing. This helps adapt your gut to the carbohydrate load and identify any potential gastrointestinal (GI) issues.
• Start Early: Begin your fueling strategy within the first 45-60 minutes of your run. Don't wait until you feel depleted.
• Consistent Intake: Aim for a regular schedule, such as one gel every 30-45 minutes. Set a watch alarm if needed.
• Hydration with Gels: Always consume gels with water. Gels are concentrated and require water for proper digestion and absorption. Without sufficient water, they can sit heavy in your stomach or even draw water into your intestines, leading to GI distress.
• Experiment with Types: Try different carbohydrate blends (glucose-only vs. glucose-fructose) and gel consistencies (some are more viscous, others are "isotonic" and thinner).
• Listen to Your Body: Pay attention to how you feel. If you experience stomach upset, try reducing the amount or frequency, or switching to a different type of gel. If you feel low on energy, you might need to increase your intake.

Potential Pitfalls and How to Avoid Them

• Gastrointestinal (GI) Distress: The most common issue.
  • Cause: Too many carbs, wrong type, insufficient water, lack of practice.
  • Solution: Practice gut training, always take with water, consider lower-carb gels initially, or gels with a glucose-fructose blend.
• Forgetting to Take Them: Easy to do when focused on running.
  • Solution: Set watch alarms, carry gels in an easily accessible place, have a clear plan.
• Over-Reliance on Gels: While effective, gels are only one part of hydration and nutrition.
  • Solution: Ensure adequate pre-race fueling, proper hydration (water and electrolytes), and consider other carb sources if gels cause issues.
• "Hitting the Wall" Despite Gels: Can still happen if intake is insufficient for your demands, or if you started fueling too late.
  • Solution: Review your hourly carb target, ensure consistent intake from the start, and ensure proper carb loading before the race.

Conclusion: Individualization is Key

There is no single magic number for how many gels you need for a marathon. The optimal strategy is highly personal and requires careful planning and extensive practice during training. By understanding the science of carbohydrate metabolism, experimenting with different products and timing, and diligently practicing your fueling strategy, you can develop a personalized plan that helps you perform your best and avoid hitting the wall on race day. When in doubt, consult with a sports dietitian or an experienced running coach.