Carb loading: What is it and how do you incorporate it before a race?
Carb Loading: What is it and how do you incorporate it before a race?
Carb loading is a widely used nutrition strategy among endurance athletes, including triathletes, to maximize muscle glycogen stores - the stored form of carbohydrates that serves as a primary fuel source during prolonged, high-intensity exercise like a triathlon.
During events such as Olympic-distance, 70.3, or full Ironman races, your body relies heavily on glycogen for energy, especially when pushing harder efforts. Normal glycogen stores can become depleted after 90+ minutes of intense activity, leading to fatigue (often called “hitting the wall”). Carb loading increases these stores by 20-40% beyond typical levels, helping delay fatigue, maintain pace longer and improve overall performance.
When and how to carb load for a race?
Most experts recommend starting carb loading 36-48 hours before your race (essentially the final 1.5-2 days), rather than a full week. This timeframe allows full glycogen super compensation without unnecessary discomfort.
Target intake: Aim for 8-12 grams of carbohydrates per kilogram of bodyweight per day during this window. Many triathletes find 8-10g/kg/day practical and effective, especially for 70.3 or Ironman distances. Key principles:
Reduce training volume (taper) while increasing carbs - the combination maximizes storage.
Focus on easy-to-digest, low-fiber carbs to avoid GI issues or bloating.
Slightly reduce fat and fiber intake to make room for more carbs without overeating calories.
Stay well-hydrated - glycogen storage binds water, so you may gain a bit of weight temporarily (this is normal and beneficial).
Recommended Food for Carb Loading
Choose familiar, tried-and-tested foods from training to minimize surprises.
Good options include:
white rice, white pasta, potatoes (mashed or baked)
Bread (white or bagels), tortillas
Oatmeal, cereals, pancakes,
Bananas, apple sauce, dried fruit
Sports drinks, fruit juices, honey/jam on toast
Energy bars, pretzels, rice cakes
Sample Day Structure
(adjust portions to hit your g/kg target):
Breakfast - Make this your biggest carb meal: oatmeal with banana + honey, toast, fruit juice
Lunch - Large portion of white rice/pasta with lean protein (chicken, fish) and simple sauce
Snacks - Bagels, sports drinks, pretzels, rice cakes
Dinner (night before) - Early and lighter: pasta, bread, potatoes, keep it low-fat/low-fiber.
On race morning (2-4 hours before start) aim for 1-3g/kg of carbs from something like toast with jam, banana, honey and a sports drink.
Recommendations
Practice first - Test your exact carb loading plan (amount, timing, foods) during a key training block or simulate race day to ensure it sits well.
Adjust by race distance - For shorter races (<90 min), a moderate increase the day before is often enough. For longer races (Half/Full Ironman), aim for the higher end.
Don’t force extreme intake - If 10-12g/kg feels impossible, 8g/kg still provides excellent benefits without discomfort. Don’t force too much overeating.
Monitor your body - Some athletes feel sluggish or bloated; dial back fiber-heavy whole grains and emphasize refined carbs in the final 24 hours.
Combine with hydration and sodium - Drink plenty and maintain electrolytes, as proper fueling includes more than just carbs.
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