You Probably Don't Need to Carb Load. Here's When You Actually Do.

Most runners carb load before every race. The science says most of them don't need to.

Your glycogen stores last roughly 75-90 minutes of hard running. Below that threshold, your normal diet handles it.

The Decision Table: Do You Actually Need to Carb Load?

Your body stores roughly 500g of glycogen across muscles and liver. That's enough fuel for about 75-90 minutes of moderate-to-hard running (Thomas et al. 2016, Burke et al. 2011).

If your race is shorter than that, your tank is already full from normal eating.

When glycogen runs low, your body shifts to burning fat. Fat burns too slowly to sustain your target race pace.

That's the wall. Carb loading delays it by topping off your fuel stores before the gun goes off.

Modifiers that change your target:

• GI issues during racing: Cap loading 2 g/kg below your tier target. If you have severe GI history, hard cap at 7 g/kg regardless of tier.
• First time carb loading: Stick to the lower end of your range. Your gut hasn't practiced processing this volume yet.
• Larger athletes (85+ kg): Cap at 8-9 g/kg. Higher daily totals become impractical to eat.

GI comfort beats perfect numbers. When in doubt, go lower.

Your Pre-Calculated Carb Targets (Zero Math Required)

Find your weight. Find your target. Done.

A 75 kg runner targeting 10 g/kg needs 750g of carbs.

That's not a pasta dinner. That's an entire day of focused eating.

The Modern Protocol (Not Your Grandpa's Pasta Party)

The 7-day depletion/loading protocol is outdated.

Bussau et al. (2002) found that a single day of 10 g/kg with minimal exercise matched the old multi-day approach in trained cyclists. No starving yourself. No depletion runs.

Areta & Hopkins (2018) reviewed 181 muscle biopsy studies. Two factors predicted glycogen storage more than anything else.

Your fitness level and how many carbs you eat beforehand.

Fitter runners have greater storage capacity. And research consistently shows 2-3 days of high carb intake paired with a taper fills the tank.

Most runners obsess over which gel to take at mile 18. Tim Podlogar, a sports nutrition researcher who advises Tour de France teams, says they're solving the wrong problem.

"The more impactful variable is the 24 hours before the gun goes off."

The Loading Timeline

Why the Activation Session Matters

That easy run or set of strides the morning before your race isn't just a shakeout. Brief exercise appears to prime your muscles to absorb and store more fuel.

Think of it as opening the door before you start shoveling carbs through it.

Podlogar uses this with Tour de France teams. A short activation session in the morning, then aggressive carb intake the rest of the day.

If you've never carb loaded before, consider spreading intake across 36 hours instead. Your gut will thank you.

My marathon protocol: activation strides the morning before, then high-carb simple foods the rest of the day. For half marathons, just a carb-focused dinner and normal breakfast.

I don't load for anything shorter. (Your Strava friends bringing pasta to a 10K don't need to either.)

What to Eat (and What to Skip)

Loading-friendly foods:

• White rice, white bread, bagels, pancakes with syrup, pretzels
• Honey, jam, maple syrup, sports drinks, fruit juice
• Gummy bears, jelly sweets, hard candy (pure sugar, zero fiber, easy way to top up)
• Bananas, rice cakes, low-fiber cereals
• Liquid carbs are underused (a tall glass of apple juice = ~55-60g carbs; a sports drink bottle adds meaningfully to your daily target)

Skip these during loading:

• Whole grains, bran, high-fiber cereals (fiber fills you up before glycogen does)
• Raw vegetables and salads (bulky, low carb density)
• Beans and legumes (gas producers on race week)
• Heavy sauces, cheese, cream, and high-fat foods (fat slows digestion)
• Large portions of meat or protein-heavy meals (not the priority)
• Alcohol (hurts hydration and sleep when both matter most)
• Anything new or spicy (race week is the wrong time to experiment)

Simple sugars pack more fuel per bite than complex carbs. Lower fiber means less fullness and more room for carbs.

Myth-Busting: Rapid Fire

"Will carb loading make me gain weight?" Temporarily, yes. Water follows glycogen into your muscles. Expect 1-2 kg on the scale. It's fuel, not fat. It disappears during the race.

"Is the pasta dinner enough for my marathon?" Probably not. A single pasta dinner provides roughly 200g of carbs. A 70 kg runner targeting 10 g/kg needs 700g. You need an entire day of carb-focused eating.

"What about the depletion phase? My coach told me to run long 3 days before and eat low-carb." Outdated protocol. Bussau et al. (2002) showed you can get the same loading from 24 hours of high-carb eating without depleting first.

"I always feel bloated race morning."

• Spread carbs across the full day instead of one giant dinner.
• Lean on liquid carbs and simple sugars. They digest faster and take up less space.
• Watch sodium from loading foods like sports drinks and pretzels. Excess sodium causes water retention.
• Sip water throughout the day to support glycogen storage.

Practical Takeaways

• 5K/10K runners: skip the pasta party. Your normal diet handles it.
• Half marathoners under 90 min: eat normally but emphasize carbs the day before.
• Half marathoners 90 min+: start a 24h loading protocol.
• Marathon runners: 24-48h structured loading at 6-10 g/kg. Scale by experience. Only proven elite loaders should push above 10.
• The modern protocol: no depletion, simple carbs, one focused day is enough.

Bottom line: The question isn't whether to carb load. It's whether your race is long enough to need it. Most races aren't.

Forward this to your running buddy who brings a pasta pot to every 5K.