Carbohydrate Loading

Carbohydrate loading (often called carbloading) is a nutritional strategy designed to maximise the amount of glycogen stored in skeletal muscle and the liver before a prolonged endurance event. When executed correctly, it can improve performance, delay fatigue and give athletes a competitive edge.

Why Glycogen Matters

During endurance exercise the body relies heavily on glycogena readily available form of glucose stored in muscle fibers and the liver. Once these stores are depleted, the intensity of effort drops sharply because the body must turn to slowerburning fuels such as fat and protein. The wall most runners feel after 90120 minutes of hard effort is essentially glycogen exhaustion.

Carbloading aims to increase muscle glycogen beyond normal levels (up to 1520% above baseline), giving athletes a larger energy reserve to draw from during the race.

The Classic TwoDay Protocol

For many years the classical method has been the goto for marathoners, triathletes and cyclists.

Day1 Depletion (Optional)

Traditional protocols start with a glycogendepleting workout (90min at 7080% VOmax) followed by a lowcarb diet (50gCHO per day). The idea is to provoke a supercompensatory effect during the loading phase.

Modern research suggests the depletion phase is not necessary for most athletes and may increase fatigue. Most coaches now skip it.

Day2 Loading

• Consume 810g of carbohydrate per kilogram of body weight (550700g for a 70kg athlete) spread over 34 meals.
• Keep protein moderate (1.2gkg) and limit fat to <30% of total calories.
• Stay hydrated aim for 3545mlkg of fluid.
• Avoid strenuous training; light activity (e.g., easy jog, stretching) is fine.

Modern 3Day EasyLoad Approach

Many athletes prefer a less aggressive plan that still yields a 2030% increase in glycogen.

Day1 HighCarb, Normal Training

Eat 57gCHOkg (350500g for 70kg) while maintaining usual training intensity. This begins the glycogen buildup without drastic diet changes.

Day2 Moderate Carbs, Reduced Volume

Consume 68gCHOkg (420560g) and cut training volume by 3040% (shorter, easy sessions). This helps store more glycogen while keeping muscles fresh.

Day3 Peak Carbs, Rest

Eat 1012gCHOkg (700840g) and rest completely or do only a very light activity (e.g., 20minute walk). This is the final topup before the event.

Choosing the Right Carbohydrate Sources

Focus on highglycemic, easily digestible carbs to speed glycogen synthesis:

• White rice, pasta, couscous
• Bagels, white bread, crackers
• Potatoes, sweet potatoes (moderateglycemic)
• Fruit juices, sports drinks, honey
• Energy gels, maltodextrin powders

Include some lowglycemic options (oats, whole grain breads, legumes) for variety, but keep the overall glycemic index high during the final loading day.

Hydration & Electrolytes

Carbohydrate storage binds waterroughly 3g of water per gram of glycogen. Expect a modest weight gain (12kg) primarily from water. Stay ahead of this by:

• Drinking 23L of fluid per day (more if the climate is hot).
• Including electrolytes (sodium, potassium, magnesium) in your drinks or meals.
• Avoiding excessive caffeine or alcohol, which can increase urine output.

Potential Pitfalls

Who Benefits Most?

Carbloading is most effective for events lasting longer than 90minutes where glycogen depletion is a limiting factor.

• Marathon & halfmarathon runners
• Longdistance cyclists (90km)
• Triathletes (especially the bike and run legs)
• Rowers, crosscountry skiers, distance swimmers

For shorter, highintensity efforts (60min) the benefit is minimal, and a regular balanced diet is sufficient.

Sample OneDay Loading Menu (70kg athlete)

Breakfast (200g CHO)

• 2 cups cooked white rice (90g CHO)
• 2 slices toast with honey (30g CHO)
• Orange juice, 250ml (30g CHO)

MidMorning Snack (150g CHO)

• Energy gel (50g CHO)
• Banana (30g CHO)
• Sports drink, 500ml (70g CHO)

Lunch (250g CHO)

• Spaghetti with tomato sauce (130g CHO)
• Garlic bread (60g CHO)
• Apple juice, 300ml (60g CHO)

Afternoon Snack (150g CHO)

• Lowfat yogurt with honey (40g CHO)
• Pretzels (50g CHO)
• Sports drink, 500ml (60g CHO)

Dinner (250g CHO)

• Grilled chicken breast (protein only)
• Mashed potatoes (120g CHO)
• Steamed white rice (130g CHO)
• Fruit cocktail, 200ml (0g CHO)

Total 1050g CHO about 15gkg for a 70kg athlete, a typical highcarb loading target.

Testing Your Carb Load

Practice the loading protocol during a training block that mimics race conditions. Observe:

• How your stomach feels during long runs.
• Any change in perceived exertion at set paces.
• Weight fluctuations (aim for 2kg gain).

Adjust the carbohydrate mix, timing, or fluid intake based on the feedback.

Quick FAQ

Can I carbload the night before a race?

Yes, but the final highcarb meal should be 23hours prerace to avoid an upset stomach.

Is supercompensation guaranteed?

Most athletes achieve a 2030% increase in muscle glycogen with proper loading; genetics and training status cause some variability.

Do I need to avoid all fats?

No, but keep fat<30% of total calories during loading days to maximise glycogen synthesis.

What about vegans?

Choose highglycemic plant foods: white rice, potatoes, fruit juices, sweetened oat milk, maple syrup, dates, and sports gels made from maltodextrin.

Bottom Line

Carbohydrate loading is a proven, lowrisk technique that can significantly boost endurance performance when done correctly. By increasing glycogen stores, you give your muscles a larger fuel reserve, delay the onset of fatigue, and improve raceday confidence. Tailor the protocol to your event length, personal tolerance, and schedule, and always test it in training before relying on it in competition.