How to fuel a race without guessing

Carb-loading works best as a build across the last few days before a race, not a single big meal the night before. Carbohydrate is stored in muscle and the liver as glycogen, and topping that store off takes more than one sitting — it takes a few days of deliberately higher carbs alongside a taper in training volume, so the fuel goes into storage instead of getting burned straight back off.

The “pasta dinner” version of carb-loading persists because it’s simple and social, but it misses the actual mechanism. Glycogen storage responds to the combination of higher carb intake and reduced training load sustained over days, not hours. One large meal the night before a race mostly just sits in your gut on race morning — it doesn’t have time to convert into stored fuel your muscles can draw on.

When should a carb-load actually start?

Roughly the last two to three days before a race, timed to overlap with your taper — the point where training volume is dropping but you haven’t stopped moving entirely. That overlap matters: a taper reduces how much glycogen your training burns off day to day, while the higher carb intake replaces and tops off the store. Doing one without the other is less effective — loading carbs into a body still training at full volume just gets burned off before it’s stored, and tapering without raising carbs leaves the store under-filled.

The exact window depends on race distance and how your training calendar is already shaped. A shorter race with a light taper needs less of a build-up than a long endurance event coming off a heavy training block. The principle stays the same regardless of distance: raise carbs as training volume comes down, not after it’s already back up.

Does everyone need to carb-load the same way?

No — the size of the carb-load should scale with the demand of the event, not apply uniformly. A long endurance race that will substantially deplete glycogen stores over its duration benefits from a real build; a shorter or lower-intensity event doesn’t need the same push, and over-loading carbs you won’t use just adds calories without adding performance. The floor-and-lift model applies here too: training days already carry a carb floor so performance doesn’t suffer day to day, and that floor lifts further specifically around a race, when performance is on the line in a way an ordinary training day isn’t.

What happens in the days right after a hard build, and does that affect race week?

This is more about the build-up into race week than the days after, but the same logic underlies both: carbs should track what your body is actually doing, not sit at a flat number regardless of context. In the run-up to a race, that means carbs climb as intensity in training drops. It’s the same principle as training-aware nutrition generally, applied to the specific, higher-stakes window of race week — the target isn’t guessing what you might need, it’s responding to where you are in the calendar.

What’s the simplest way to think about race-week fueling?

Treat carb-loading as a planned build tied to your calendar, not an improvised decision the night before. Know roughly when your taper starts, raise carbs to overlap with it, and size the build to the actual demand of the race — bigger for a long endurance event, smaller for something shorter. The goal isn’t to eat as many carbs as possible in the final 48 hours; it’s to have glycogen stores topped off by the time the race starts, built deliberately over the days that matter.

How Sweatmeal does this

Sweatmeal builds carb-load and fuelling plans around your training calendar — long runs, race week, taper — so carbs lift automatically as performance is on the line, then settle back once the race has passed. You don’t have to remember when to start the build or guess how big it should be; the plan reads your calendar the same way your daily target reads your training load. See how the underlying calculation works on our methodology page.