The Science of Carbohydrate Loading
Carbohydrate loading is a strategy endurance athletes use to maximize glycogen storage in their muscles and liver. Glycogen is the main fuel for muscles during prolonged exercise, and running out of it (hitting the wall) means switching to less efficient fat burning. Increasing carbohydrate intake before a race fills your fuel tank, delaying fatigue and improving performance.
Unlike older methods, modern carb loading doesn't require a low-carb phase. It focuses on increasing carbs while reducing exercise volume in the final days before an event.
Determining Your Carbohydrate Needs
For events over 90 minutes, aim for 8–12 grams of carbohydrates per kilogram of body weight per day during the loading phase. Shorter events generally don't require carb loading. For example, a 70 kg athlete would target 560 to 840 grams of carbs daily. Distributing this intake across multiple smaller meals and snacks helps avoid feeling too full.
Timing Your Carb Load
Start carb loading 36 to 72 hours before your race, depending on the event length. For a Sunday marathon, begin around Thursday morning. This timing aligns with your tapering phase. A large pasta dinner the night before is not enough on its own and can cause discomfort; carb loading is a multi-day process.
Choosing the Right Carbohydrates
Focus on easily digestible, low-fiber carbohydrates to maximize glycogen and avoid GI issues. Opt for white grains over whole grains for less fiber.
Best Carb-Loading Foods:
- White pasta and rice
- White bread and bagels
- Oats and low-fiber cereals
- Peeled potatoes
- Bananas
- Dried fruit
- Fruit juice and sports drinks
- Low-fat yogurt
Foods to Limit or Avoid:
- High-fiber vegetables
- High-fat foods
- High-protein foods
- New or unfamiliar foods
Hydration and Avoiding Bloating
Hydration is key, as each gram of stored glycogen holds 3 grams of water. A slight weight gain (1-2 kg) is normal and reflects this vital water storage. Increase fluid intake and consider consuming some carbs through sports drinks or juice.
| Meal | Standard Training Day | Carb-Loading Day (Target: 8g/kg) |
|---|---|---|
| Breakfast | Oatmeal with berries, handful of nuts | Large bowl of oatmeal with banana, drizzle of honey, glass of juice |
| Lunch | Chicken salad sandwich on whole-wheat bread | Large portion of white rice with lean chicken breast |
| Dinner | Salmon with roasted sweet potatoes and broccoli | Large bowl of white pasta with tomato-based sauce, side of peeled potatoes |
| Snacks | Apple with peanut butter | Bagel with jam, pretzels, or energy bars |
Practicing Your Race-Week Nutrition
Test your carb-loading strategy during long training runs to see how your body reacts to specific foods, timing, and portion sizes. Avoid trying a new plan on race week.
The Race Morning Meal
Eat an easily digestible, low-fiber, high-carb meal 2-4 hours before the race to top up liver glycogen. Options include a bagel with jam, oatmeal, or a liquid carb drink. Stick to familiar foods. You may need to wake up early for an early race.
Conclusion
Proper carb loading involves more than just a pre-race pasta dinner. A gradual increase in low-fiber carbohydrates over 2-3 days, combined with tapering, effectively boosts glycogen stores. Choosing easily digestible foods, staying hydrated, and practicing your plan during training are crucial for optimal performance. This strategy is a vital part of your race preparation. You can read more about comprehensive fueling strategies for endurance athletes at the American College of Sports Medicine.
