Fueling properly is one of the most critical yet confusing aspects of endurance sports. Whether you’re tackling a marathon, triathlon, or an ultra-cycling event, your body’s performance hinges on how well you nourish it.
I’ve learned firsthand that the wrong fueling strategy can leave you fatigued and underperforming, while the right one can unlock a new level of stamina and recovery.
Let’s explore the balance between carbohydrates, protein, and fats and how each plays a vital role in keeping endurance athletes at their peak.
The Basics of Fueling Endurance
Your body is like a machine that thrives on the right kind of energy. According to ISSA, endurance athletes need a combination of carbohydrates, protein, and fats to perform well, recover quickly, and avoid injury. These three macronutrients each serve a unique purpose, and finding the right balance can transform your training and race-day performance.
- Carbohydrates act as your primary source of energy, particularly for high-intensity activities.
- Protein steps in to repair the wear and tear your muscles endure after a long workout.
- Fats, often overlooked, are essential for longer, lower-intensity efforts and overall body function.
Carbs Are The Base
As stated by Elizabeth Quinn, MS, carbohydrates are the body’s preferred energy source for a reason—they’re quick, efficient, and easy to metabolize. Stored in your muscles as glycogen, carbs fuel everything from your morning runs to long-distance cycling adventures.
However, glycogen stores are limited, which means you’ll need to replenish them regularly during prolonged efforts to avoid running out of steam.
Simple Carbs
Simple carbohydrates provide fast energy because they’re broken down quickly in the body. Think fruit, candies, and sports drinks. These are especially useful during high-intensity or long-duration workouts when your glycogen levels drop, and you need an immediate energy boost.
They’re not ideal as a primary energy source because they burn out quickly.
Complex Carbs
Complex carbs take longer to digest, offering sustained energy over time. They’re found in foods like whole grains, beans, and legumes. Incorporating these into your meals ensures your glycogen stores are topped off before a big training session or race.
They’re your best bet for maintaining consistent energy levels throughout the day.
How Much Do You Need?
For endurance athletes, carb requirements are much higher than for the average person. ISSA suggests to aim for 8-10 grams of carbs per kilogram of body weight daily if you’re regularly engaging in endurance training.
For ultra-endurance events lasting four hours or more, you may need to hit the upper end of that range to keep your energy reserves from depleting.
Protein Is The Repair Crew
Protein is essential for recovery, but its importance goes beyond that. After a tough workout, your muscles are like a torn-up battlefield. Protein swoops in to rebuild and strengthen them, helping you recover faster and reduce soreness. It also plays a backup role during long events, serving as an energy source when carb stores run low.
Protein Sources
| Type of Protein | Description | Examples | Considerations |
| Animal-Based Proteins | Complete proteins containing all essential amino acids needed by the body. | Chicken, fish, eggs, dairy | Excellent for recovery meals and building muscle; easily meets amino acid requirements. |
| Plant-Based Proteins | Often incomplete proteins; plant-based athletes may need to combine sources to obtain all amino acids. | Quinoa, lentils, almonds, chia seeds | Combining different protein sources is important; high-quality protein powder can help fill gaps. |
How Much Do You Need?
According to NCBI, the general recommendation for endurance athletes is 1.4 grams of protein per kilogram of body weight daily. For those following a plant-based diet, you may need to bump this up to 2 grams per kilogram, since plant proteins are often less bioavailable.
Including protein in every meal and snack ensures your muscles have the tools they require for repair and growth.
Fats – The Energy Source
Fats may not have the quick energy punch of carbs, but they’re crucial for endurance athletes, especially during lower-intensity, long-duration activities. They’re a more efficient fuel source for the body when exercise intensity drops.
Additionally, fats support essential bodily functions, including hormone regulation, cell repair, and the absorption of fat-soluble vitamins.
Sources of Healthy Fats
- Avocado: A perfect pre-run toast topper or post-run recovery addition.
- Nuts and Seeds: Snackable, portable, and packed with nutrients.
- Fatty Fish: Salmon and mackerel not only provide healthy fats but are also rich in omega-3s, which reduce inflammation.
How Much Do You Need?
Limit saturated fats, such as those from butter and fatty meats, to maintain cardiovascular health. Fat isn’t just a backup energy source—it’s vital for your overall well-being.
Timing Is Everything
What you eat is only part of the equation, when you eat matters just as much. Proper timing of carbs, protein, and fats can significantly impact your energy levels and recovery.
Before Your Workout
About two hours before training, consume 1 gram of carbs per kilogram of body weight. Pair this with 20 ounces (0.76 kg) of water to ensure you’re well-hydrated. A slice of toast with peanut butter, a banana, or a small bowl of oatmeal can provide the perfect pre-workout boost without weighing you down.
During Your Workout
For workouts lasting over an hour, sip on fluids containing carbs and electrolytes every 20 minutes. A sports drink or chewable energy gel works wonders for maintaining stamina. Adding electrolytes helps prevent cramping and ensures your muscles fire properly.
After Your Workout
Recovery begins the moment you stop moving. Within 30 minutes, aim for 1.5 grams of carbs per kilogram of body weight and 15-25 grams of protein. This combination replenishes glycogen stores and kickstarts muscle repair. Wash it down with plenty of water—about 24 ounces for every pound of body weight lost during exercise.
Micronutrients and Hydration
While carbs, protein, and fats steal the show, vitamins, minerals, and fluids quietly play an equally important role. Without proper hydration and micronutrient levels, even the best diet won’t carry you through an intense session.
Nutrient
Purpose
Sources
Additional Notes
Vitamin C
Boosts immunity and aids in recovery.
Oranges, strawberries, bell peppers
Supports overall recovery and immune function.
Vitamin D
Essential for bone strength.
Sunlight, fortified milk, fatty fish
Sun exposure is a natural source; supplements may be needed in low-sun areas.
Electrolytes
Replenish nutrients lost through sweat.
Bananas (potassium), soups (sodium), yogurt (calcium)
Crucial for muscle function and hydration.
Methodology
I pulled the information in this article from both research and my own experiences as someone who’s spent countless hours experimenting with nutrition during long runs and bike rides. I know how overwhelming it can be to sift through all the information out there, so I focused on breaking things down into clear, relatable steps that you can actually use.
Every tip here has either worked for me or is something I wish I’d known earlier in my endurance journey
Find What Works for You
Every athlete is different, and nutrition isn’t a one-size-fits-all solution. Experiment with different food combinations and timing during training (not on race day). Track how your body responds, adjust based on performance and recovery, and give yourself grace to learn through trial and error.
Sources
- ISSA – Endurance Athlete Diet: What to Eat for Optimal Performance
- Very Well Fit – Sports Nutrition for Endurance Exercise
- NCBI – International Society of Sports Nutrition position stand: protein and exercise
