Carb-loading gets treated like a single big pasta dinner the night before a race, but that's not really how it works, and done that way it barely helps. Real carb-loading is about maximizing your glycogen stores over the 1-3 days before an event, so you start the race with a full tank instead of running it down mid-race.
Why it matters
Your muscles and liver store carbohydrate as glycogen, and it's your primary fuel source for anything above an easy pace. A normal diet keeps glycogen stores at a moderate level, enough for day-to-day training, but not maxed out. For events lasting longer than 90 minutes, starting with fully saturated glycogen stores measurably delays fatigue and protects performance late in the race.
The basic protocol
- 1-3 days before the race: Increase carbohydrate intake to roughly 8-12g per kilogram of bodyweight per day. For a 70kg athlete, that's 560-840g of carbs a day, well above normal training intake. While a single 24-hour period of aggressive loading (around 10g/kg) paired with complete physical inactivity can fully saturate glycogen stores, spreading the volume over 2–3 days is often easier on the digestive system.
- Taper your training volume Glycogen loading works when you're eating more carbs while burning through less of them, if you're still training hard, you're just replacing what you burn rather than building a surplus.
- Keep it to familiar foods. Rice, pasta, bread, potatoes, oats. This is not the time to test a new diet.
The part people get wrong: WATER
Glycogen is highly hydrophilic, meaning it holds onto water as it is stored in the body, roughly 3g of water for every gram of glycogen. That's normal and expected, it's part of why carb-loading works, that stored water becomes available fluid during the race. But it also means carb-loading without also increasing fluid intake leaves you under-hydrated relative to what your body's trying to store. Drink normally to slightly more than normal across the loading days, not less.
Carb-loading vs. race-day fueling: two different things
This is the most common confusion. Carb-loading is about what you eat in the days before the race to maximize stored glycogen. Race-day fueling is what you consume during the event to top up what you're actively burning, gels, chews, or drink mixes at regular intervals. You need both, and they're not interchangeable, a big carb-loaded breakfast doesn't replace taking gels during a 3-hour race.
For the during-race side, products like Isocarb or the Carbo Gel range are built specifically for fast absorption mid-effort, which is a different job than the slow-digesting meals you'd eat while loading.
Common mistakes
- Only doing it the night before. One meal doesn't meaningfully shift glycogen stores. It needs 1-3 full days.
- Loading up on fiber and fat along with the carbs. A huge fiber-heavy pasta salad or a fatty sauce slows digestion and raises the risk of race-morning GI issues. Keep loading meals simple and carb-forward.
- Forgetting to taper training. Carb-loading while still doing hard sessions just replaces burned fuel instead of building a surplus.
- Under-drinking. Remember the 3:1 water-to-glycogen ratio, cutting fluids while loading works against the process.
Get the loading days right, and the fueling strategy you've already trained your gut for during training carries you the rest of the way. See our full Carbs & Energy Gels collection for race-day options.
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