Review of Carb-Loading Strategies Before Races (Advanced Guide)

Carb-loading is a running classic—but many athletes still do it poorly (hello, giant pasta bowl at 10 p.m.). This deeper review refines what to do, when, and for which race distances, so you top up glycogen without topping out your gut.

Why Carb-Loading Works

Glycogen powers moderate-to-high intensity efforts. Well-designed loading can raise muscle glycogen beyond everyday levels (“supercompensation”), delaying the point where you’re forced to slow because stores run low. Each gram of glycogen binds ~3 g water—useful for thermoregulation, but it explains the 1–2 kg pre-race weight bump.

Distance-Specific Strategies

• 5K/10K: Traditional loading isn’t necessary; a normal high-carb day pre-race plus a carb-rich pre-race meal/snack suffices.
  
  
• Half marathon: Mild loading helps—48 hours at ~6–8 g/kg/day carbohydrates alongside taper.
  
  
• Marathon / 50K+: Go deliberate—48–72 hours at ~8–10 g/kg/day with reduced training volume.
  
  

(“g/kg/day” = grams of carbohydrate per kilogram of body mass per day.)

The 3-Day Marathon Template

T-3 and T-2 days:

• Carbs at 8–10 g/kg/day, moderate protein, low-to-moderate fat.
  
  
• Choose low-fiber, low-residue sources (white rice/pasta, potatoes, tortillas, bananas, low-fat dairy, smoothies).
  
  
• Salt food to aid fluid retention; sip fluids steadily.
  
  

T-1 day:

• Keep carbs high but meals smaller and earlier; avoid experimental foods.
  
  
• Walk/short shake-out only; no heroic strides.
  
  
• Lay out race fuel and hydration plan.
  
  

Race morning (2–3 h pre-start):

• 1–4 g/kg carbohydrates depending on tolerance/time—think toast + honey, rice + eggs, oats + banana.
  
  
• Small top-up 15–20 minutes before the gun if needed (gel/chews), then follow your in-race fueling cadence.
  
  

Gut-Training: The Missing Link

Many “carb-loading failures” are really GI tolerance failures. During build-up, practice:

• Eating more carbs per hour while running (work up toward 60–90 g/h for marathons/ultras if appropriate).
  
  
• Fuel textures (gels vs chews vs drink mixes) and flavors to avoid palate fatigue.
  
  
• Fluid–sodium pairing so gut absorption keeps pace with intake.
  
  

Common Mistakes (and Fixes)

• Pasta party overkill late at night: Finish heavier carbs earlier in the day, keep dinner modest.
  
  
• High fiber choices: Save beans/salads/brans for after race day.
  
  
• Neglecting sodium: Salt helps retain fluid; include it with meals and pre-race drink.
  
  
• Too little fluid: Carb storage needs water—steady sipping > chugging.
  
  
• Macros drift: Keep protein moderate (not high) and fat relatively low to speed gastric emptying.
  
  

Special Cases

• Hot races: Slightly higher fluids/electrolytes during loading; accept the extra water weight—it’s protective.
  
  
• Low-FODMAP needs: Choose white rice, potatoes, sourdough, rice-based cereals, maple syrup; avoid high-FODMAP fruits/sweeteners.
  
  
• Morning stomachs: Spread carbs the day before and rely on an earlier, simpler pre-race snack.
  
  

Verdict

Effective carb-loading is boring, early, and practiced. Match the load to the distance, go low-fiber and familiar, pair with fluids and sodium, and rehearse the approach in long-run dress rehearsals. Do that, and “the wall” shows up later—or not at all.

- Edward