You’ve trained for months, tapered perfectly, and laid out every piece of race gear. Then you destroy all that preparation with pre-race carb loading mistakes that leave you bloated, sluggish, and racing to the bathroom at mile 15. These seven errors sabotage more ultra marathons than undertrained legs ever could—and they’re completely preventable.
Mistake #1: Starting Carb Loading Too Late
The biggest pre-race carb loading mistake is cramming carbohydrates into 48 hours. Your body needs 5-7 days to fully maximize glycogen storage, not 2-3 days.
The Science: Research shows that progressive carbohydrate loading over 7 days increases muscle glycogen stores by 15-20% compared to 3-day protocols. That translates to an extra 30-45 minutes of glycogen-fueled running before bonking.
Fix: Begin increasing carbohydrate intake 7 days before your ultra, targeting 5-7g per kg bodyweight days 7-5, then 8-10g/kg days 4-2, and 6-8g/kg the day before.
Mistake #2: Eating Too Much Fiber During Peak Loading
Whole wheat pasta, brown rice, and vegetables seem like healthy carb-loading choices. They’re actually pre-race carb loading mistakes that cause race-day GI disasters.
The Problem: Fiber slows gastric emptying and increases stool bulk. During race week loading (days 4-2 before), excess fiber creates intestinal bulk that causes urgent mid-race bathroom stops.
Fix: Switch to low-fiber, easily digestible carbohydrates during peak loading days: white rice, white bread, pasta, potatoes (without skin), white bagels, and low-fiber cereals.
High-Fiber vs Low-Fiber Carbs
Avoid during days 4-2: Whole wheat products, beans, cruciferous vegetables, high-fiber fruits Choose instead: White rice, white bread, white pasta, potatoes, bananas, melon, diluted fruit juice
Mistake #3: Overloading on Fat and Protein
The “pizza party” the night before a race is one of the most common pre-race carb loading mistakes. That deep-dish pizza is primarily fat and protein with moderate carbs.
The Math: A typical large pizza slice contains: 35g carbs, 12g fat, 15g protein. You’d need to eat 12-15 slices to reach your carbohydrate target—consuming 150g+ fat that slows digestion for 24+ hours.
Fix: Keep fat under 20% of total calories during peak loading (days 4-2). Choose plain pasta with marinara, rice with lean chicken, bagels with jam, not creamy sauces, cheese-heavy dishes, or fried foods.
Mistake #4: Forgetting Sodium and Electrolytes
Carbohydrate loading requires adequate sodium to pull glycogen and water into muscle cells. Low-sodium carb loading is a pre-race mistake that leaves you under-hydrated despite drinking plenty.
The Science: Every gram of stored glycogen binds 3-4g of water. Inadequate sodium prevents optimal glycogen storage and causes dehydration.
Fix: Add salt liberally to carb-loading meals. Target 4,000-6,000mg sodium daily during peak loading. Use salty broths, pickles, pretzels, and salted rice to increase sodium alongside carbohydrates.
Mistake #5: Trying New Foods During Race Week
Your neighbor swears by her special quinoa bowl recipe. Race week is absolutely not the time to discover you’re sensitive to quinoa.
The Risk: New foods can trigger allergies, sensitivities, or simply not digest as expected under pre-race stress and altered routine.
Fix: Eat only foods you’ve successfully consumed before long training runs. Race week nutrition should be boring and predictable—save culinary adventures for after your ultra.
Mistake #6: Drastically Increasing Meal Size
Eating three massive meals daily during carb loading guarantees bloating and GI distress—a critical pre-race carb loading mistake.
The Problem: Your digestive system can’t suddenly process 2,000-calorie meals. Large meals sit in your stomach for hours, causing discomfort and reduced appetite for subsequent meals.
Fix: Spread carbohydrate intake across 5-6 smaller meals and snacks. This improves digestion, maintains steady blood sugar, and prevents the “too full to eat” feeling that limits total carb intake.
Sample Day 3 Before Race (70kg runner, 650g carb target)
- Breakfast: Oatmeal with banana and honey (80g carbs)
- Mid-morning: Bagel with jam (60g carbs)
- Lunch: White rice with grilled chicken (110g carbs)
- Afternoon snack: Sports drink and rice cakes (60g carbs)
- Dinner: Pasta with marinara sauce (140g carbs)
- Evening: Fruit smoothie with dates (80g carbs)
- Throughout day: Sports drink (120g carbs)
Mistake #7: Dehydrating While Carb Loading
The most overlooked pre-race carb loading mistake is inadequate hydration. Glycogen storage requires water—you can’t properly carb load while dehydrated.
The Numbers: Storing 500g glycogen requires 1,500-2,000ml water. If you’re not urinating frequently with pale yellow urine, you’re not loading properly.
Fix: Drink 3-4 liters fluid daily during carb loading, primarily water and sports drinks. Monitor urine color—it should be pale yellow throughout loading days.
Key Takeaways
- Start carb loading 7 days before race, not 48 hours
- Switch to low-fiber carbs (white rice, white bread) during days 4-2 before race
- Keep dietary fat under 20% during peak loading to maximize carbohydrate storage
- Consume 4,000-6,000mg sodium daily to facilitate glycogen and water storage
- Eat only familiar, tested foods—never experiment during race week
- Distribute carbs across 5-6 smaller meals instead of 3 massive ones
- Drink 3-4 liters daily; dehydration prevents optimal glycogen storage
Get Your Carb Loading Right
Pre-race carb loading mistakes cost you hours on race day that perfect training can’t overcome. Start early, choose low-fiber carbs, moderate fat intake, maintain sodium, stick to familiar foods, eat frequently, and stay hydrated. These simple principles separate runners who bonk at mile 40 from those who finish strong at mile 100.
Test your carb loading protocol before a dress rehearsal long run 4-6 weeks before your goal race. This reveals individual tolerance issues and allows refinement before it actually matters.
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