Carb Loading

Eating extra carbohydrates 2–3 days before a long race to maximize glycogen stores.

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Understanding Carb Loading

Carb loading is the practice of eating extra carbohydrates in the 2–3 days before a long race (half marathon or longer) to maximize your muscle glycogen stores. When done correctly, it increases glycogen reserves by 20–40%, giving you more fuel before bonking becomes a risk.

Modern carb loading is much simpler than the old "depletion and supercompensation" protocol from the 1970s. You don't need to deplete glycogen first. Simply increase your carbohydrate intake to 7–10 grams per kilogram of body weight per day for 2–3 days before the race while reducing training volume (which you're doing anyway during the taper).

This means a 150-pound (68 kg) runner should consume 475–680 grams of carbs per day — roughly 1,900–2,700 calories from carbs alone. Focus on easily digestible sources: white rice, pasta, bread, potatoes, pancakes, and sports drinks. Reduce fiber and fat to make room. Many runners gain 2–4 pounds during carb loading — this is normal and represents water stored alongside glycogen.

Key Facts: Carb Loading

Key facts and insights about carb loading that every endurance athlete should know.

Target

Target: 7–10 grams of carbohydrates per kilogram of body weight per day for 2–3 days

Increases glycogen stores by 20–40% comp

Increases glycogen stores by 20–40% compared to a normal diet

Weight gain of 2–4 pounds is normal and

Weight gain of 2–4 pounds is normal and is mostly water stored with glycogen

Only beneficial for races lasting 90+ mi

Only beneficial for races lasting 90+ minutes (half marathon and longer)

Pro Tips: Carb Loading

Practice carb loading before a training long run so you know what foods agree with you

Focus on low-fiber, white-flour carbs: white rice, white pasta, white bread, pancakes

Reduce fat and protein to make room for carbs without overeating total calories

Start 2–3 days before the race, not just the night before — one pasta dinner isn't enough

Frequently Asked Questions About Carb Loading

No. These races are short enough that your normal glycogen stores are sufficient. Carb loading is only beneficial for races lasting 90 minutes or longer. For shorter races, just eat a normal, balanced pre-race meal.

A familiar, carb-heavy, low-fiber meal. Classic choices: pasta with plain sauce, white rice with chicken, or a large plate of pancakes. Avoid trying new foods, high-fiber vegetables, spicy dishes, or alcohol. Eat dinner early enough (5–6 PM) to fully digest before bed.