Why Carbohydrates Are Non-Negotiable for Your Marathon
For endurance events like a marathon, carbohydrates are the body’s primary and most efficient fuel source. They are stored in your muscles and liver as glycogen, providing the quick energy needed for sustained effort. A typical runner's glycogen stores can sustain 60 to 90 minutes of running at moderate intensity before depletion becomes a significant factor. As these stores run low, your body begins to slow down, and you risk a dramatic drop in performance known as 'hitting the wall'.
Replenishing these glycogen stores during the race is therefore critical. Simply put, ingesting carbohydrates during your run helps maintain blood glucose levels, delaying fatigue and allowing you to sustain a higher intensity for longer. Failing to fuel properly can compromise your energy, concentration, and ultimately, your finishing time.
The Golden Rule of Marathon Carbs: 30 to 90+ Grams Per Hour
The amount of carbohydrates you need per hour depends on the duration and intensity of your race, as well as your personal tolerance. Sports nutrition guidelines have evolved over time, offering more specific advice than ever before.
- For moderate intensity efforts lasting 1–2 hours, the recommendation is to consume approximately 30–60 grams of carbohydrates per hour. For many runners, this is a sufficient starting point that can be achieved with standard energy gels, chews, or drinks.
- For longer and more intense marathons lasting over 2–2.5 hours, higher intake rates of 60–90 grams of carbs per hour are recommended. This strategy has been linked to better performance outcomes for faster and more experienced athletes.
- For highly trained or elite athletes, some studies show performance benefits from consuming up to 120 grams of carbohydrates per hour during ultra-endurance events. This is an advanced strategy requiring significant 'gut training.'
To achieve the higher intake rates of 60+ grams per hour, you must use a fueling product containing a mix of different carbohydrates, such as glucose and fructose. These 'multiple transportable carbohydrates' use different intestinal pathways for absorption, allowing your body to process more fuel per hour without causing gastrointestinal distress. A common and effective ratio is 2:1 glucose to fructose.
Putting Your Fueling Strategy Into Action
- Start Early: Don't wait until you feel depleted. Start consuming carbohydrates within the first 30 minutes of your marathon. Consistent, early intake prevents your glycogen stores from dipping too low. Runners often get distracted by the race atmosphere and forget to fuel until it's too late.
- Fuel Regularly: Aim for a steady intake every 30 to 40 minutes. The exact frequency depends on the type and quantity of fuel you are consuming. If using a gel, consider sipping it over a few minutes rather than all at once to aid absorption.
- Practice in Training: You must test your race-day fueling plan during your long training runs. Experiment with different products and quantities to see what works best for your digestive system. Never try a new product or strategy on race day.
- Pair Carbs with Hydration: Always take water with energy gels to help with digestion and absorption. If relying on sports drinks for carbs, ensure they also contain electrolytes to replace lost sodium.
Fuel Source Comparison: Gels, Chews, Drinks, and Real Food
Your choice of fuel comes down to personal preference, tolerance, and the amount of carbohydrates you need to consume. Here is a comparison of common options:
| Fuel Source | Carbohydrate Content | Pros | Cons |
|---|---|---|---|
| Energy Gels | ~20-30g per gel (variable) | Quick-acting, portable, and easy to consume. | Can cause GI distress, often requires water, taste fatigue. |
| Energy Chews | ~20-30g per serving (e.g., 3-4 chews) | Solid food feel, easy to portion, often have electrolytes. | Slower to consume, can get sticky, may cause jaw fatigue. |
| Sports Drinks | ~20-60g per bottle (depending on concentration) | Provides hydration, electrolytes, and carbs simultaneously. | Requires carrying a bottle, can be heavy, less carb-dense than gels. |
| Real Food (e.g., Banana) | ~25g per medium banana | More natural, can provide a more satiating experience. | Can be bulky to carry, slower to digest, potential for GI issues due to fiber. |
The Advanced Strategy: Gut Training
Recent research suggests that the gut is adaptable and that you can 'train' it to increase its capacity to absorb carbohydrates during exercise. Athletes who consistently consume higher-carbohydrate diets and practice consuming carbs during training sessions show increased carbohydrate oxidation rates. This is why some elite athletes can comfortably tolerate 90+ grams per hour during competition.
To train your gut, gradually increase your carbohydrate intake during long runs over your training cycle. This allows your digestive system to adapt to higher volumes of fuel without discomfort. This process can significantly reduce the risk of stomach issues on race day.
Conclusion
Fueling for a marathon requires a strategic approach tailored to your body and race goals. While individual needs vary, the science points to a clear pathway: start with 30-60 grams of carbs per hour for efforts under two hours, and increase to 60-90 grams per hour for longer events, ideally using a mix of glucose and fructose for maximum absorption. The most important takeaway is to consistently practice your fueling strategy during training. By starting early, fueling regularly, and using multiple carbohydrate sources, you can effectively manage your energy stores and run strong all the way to the finish line. For more detailed guidance, consider consulting with a sports dietitian.
