Carbohydrate loading—or "carbing up"—is one of the most misunderstood strategies in endurance sports. Done correctly, it can add 2-5% to your race performance. Done wrong, it leaves you bloated at the start line.

Why Carbs Matter in the Final Days

During a race lasting more than 90 minutes, your glycogen stores become the limiting factor for performance. Elite cyclists and triathletes can burn through their liver and muscle glycogen in 2-2.5 hours, even with on-race fueling.

The science is clear: a 2010 study in the *Journal of Applied Physiology* found that athletes who entered races with super-compensated glycogen levels maintained higher power output in the final 30 minutes compared to those on baseline carb intake.

The Three-Day Window

Carb loading doesn't start 24 hours before your race—it starts three days out. Here's why:

Days 3-2 Before Race (Moderate Phase):

Increase carbs to 7-8g per kg of body weight

Maintain normal training volume but reduce intensity

This "primes" your muscles to accept extra glycogen

Day 1 Before Race (Peak Phase):

Bump carbs to 10-12g per kg of body weight

Keep intensity very low—maybe a 15-minute shakeout run or easy spin

Eat familiar, easily digestible carbs: pasta, rice, bread, fruits

Race Morning:

Eat a light carb meal 2-3 hours before start (bananas, toast with jam, oatmeal)

Don't try anything new

The Practical Formula

For a 70kg endurance athlete, the progression looks like this:

Three Days Before:

490g carbs/day (7g × 70kg)

Example: 150g breakfast (oatmeal+berries), 150g lunch (pasta), 150g dinner (rice+veggies), 40g snacks

Two Days Before:

560g carbs/day (8g × 70kg)

Slightly higher at each meal, keep protein moderate

Day Before:

700-840g carbs/day (10-12g × 70kg)

3-4 large carb meals, minimal fiber to avoid GI issues

This seems high—and it is. But this is temporary, targeted loading, not permanent diet change.

What to Eat (And What to Avoid)

Best carb-loading foods:

White rice and pasta (easier to digest than brown varieties)

White bread, bagels, English muffins

Bananas, dates, canned peaches (low fiber)

Honey, jam, sports drinks

Potatoes (peeled, if needed)

Avoid during loading:

High-fiber vegetables and fruits

Whole grain bread and cereals

Fatty meats (slows digestion)

Excessive caffeine and alcohol

Anything you haven't tested before

The goal is maximum glycogen, minimal GI distress.

The Hydration Component

Carbohydrate loading pulls water into muscle tissue—this is intentional and good. But it also increases fluid needs. Drink to thirst during the loading phase, and aim for pale-colored urine. Many athletes naturally drink more when eating more carbs.

When Carb-Loading Backfires

Common mistakes:

Starting too early (5+ days out): your muscles stop accepting extra glycogen

Using high-fiber foods: leads to bloating and GI issues on race day

Overestimating how much you need: a 60-minute race doesn't benefit from aggressive loading

Not testing it in training: your gut needs to adapt to high carb intake

For Specific Race Distances

The protocol above works best for races 2+ hours long (70.3 triathlons, marathons, 100km cycling events). Shorter races see diminishing returns:

**Races under 90 minutes:** Standard diet is fine; no aggressive loading needed

**Races 90-180 minutes:** Moderate increase (5-7g/kg) for 1-2 days

**Races 180+ minutes:** Full protocol described above

Monitoring with Your Training Data

Many athletes overlook this: your [training load data](/) becomes crucial during carb-loading. If you're also completing a final taper workout, you should see a drop in Training Stress Balance (TSB) a few days out—this is exactly when you want to begin carb loading. The depletion from the taper combined with high carb intake creates the perfect super-compensation effect.

The Bottom Line

Carb-loading isn't magic, but it's backed by decades of sports science. If you're racing more than 2 hours, a structured 3-day carb increase to 10-12g per kg can meaningfully improve your finish-line power. Start the practice in training, dial in the foods that work for your gut, and execute with precision three days before race day.

Your race-day nutrition strategy should [begin weeks before](/) with understanding your sweat rate, fueling needs, and gut tolerance. The final carb-loading phase is simply the final tuning step.

How to nail your carb loading strategy