Carb loading means filling your glycogen stores all the way before a long race — topping off the tank, not stuffing yourself. The work happens in the final 36 to 48 hours: training tapers, carbs climb to roughly 3.5 to 5.5 grams per pound of body weight per day, and fiber and fat step aside to make room. One pasta dinner doesn't do it. Two easy days of carb-forward eating does.
What is carb loading, actually?
Your body stores carbs as glycogen — enough for roughly 90 minutes to two hours of work at effort. A marathon outlasts that tank, so the goal of the final days is simple: arrive at the start line with it completely full. That's all carb loading is — topping off stores that normal training keeps partly drained. It is not eating as much as possible. Your total calories barely change; the mix changes. Carbs take over the plate space that fat, fiber, and second helpings of protein usually hold. If the fueling basics are new to you, start with Endurance Nutrition 101 — loading is just the pre-race half of the same math.
When should you start carb loading?
The final 36 to 48 hours before the gun — one to three days, depending on how you like to spread it. The timing isn't arbitrary: it only works because your training has tapered. With almost no long efforts left on the schedule, the carbs you eat go into storage instead of getting burned the same afternoon, and the tank climbs day over day. Start a week out and you're not loading, you're just eating; your body can't stockpile glycogen that far ahead. Two focused days beat seven vague ones.
How much should you eat — in real meals?
The sports-science consensus lands at roughly 3.5 to 5.5 grams of carbs per pound of body weight per day — the research states it as 8 to 12 grams per kilogram: the International Society of Sports Nutrition puts it at 8 to 10 over one to three days, and Olympic-committee guidance runs 10 to 12 for the final 36 to 48 hours. For a 150-pound runner that's about 550 to 800 grams of carbs a day, and the low end is plenty for most of us who aren't chasing a podium. On a plate, a day near the low end looks like this:
| Meal | What it looks like | Rough carbs |
|---|---|---|
| Breakfast | Big bowl of oatmeal with banana and honey, glass of orange juice | ~120g |
| Snack | Bagel with jam | ~70g |
| Lunch | Generous rice bowl with chicken, plus lemonade | ~130g |
| Snack | Pretzels and a bottle of sports drink | ~80g |
| Dinner | Big plate of pasta with simple tomato sauce, bread on the side | ~150g |
| Evening | Bowl of cereal or toast with honey | ~50g |
Notice what's doing the work: white rice, pasta, bread, juice, pretzels — simple carbs, easy volumes. Liquids count too, and juice or a carb drink is the easiest way to close the gap when your stomach says the plate is full. This is the one stretch of the training block where the "plain" carbs are exactly the right call.
Doesn't the pasta dinner take care of it?
The pasta dinner is the most famous meal in running, and it can't do the job alone. Even a generous plate carries maybe 150 grams of carbs — a fraction of a loading day. If the night-before dinner is your entire plan, you line up with the tank half full and find out around mile 20. The dinner is the finale of the load, not the load itself — what to eat the night before a race covers how to get that last meal right.
Why did the scale jump two pounds?
Because it's working. Glycogen is stored with water, so a proper load typically adds 1 to 3 pounds on the scale. Your scale will lie to you for 48 hours — let it. That water isn't dead weight; it's fluid your body carries into the race and draws on as the glycogen burns. Your legs might feel full and a little heavy on the shakeout jog, and that's the feeling of a topped-off tank, not lost fitness. Feature, not bug.
What should you avoid while carb loading?
- New foods. Race week is not the week to discover a new cuisine. Load on foods your gut already knows.
- Fiber-heavy meals. Big salads, beans, bran-anything — fiber fills you up before the carbs get in, and it can keep your gut busy on race morning.
- Fat-heavy meals. Cream sauces and fried food crowd out carbs and sit around longer than you want them to.
- Forcing the top of the range. If the top of the range has you miserable, back off — 3.5 grams per pound with a happy stomach beats 5.5 with an angry one.
Do you need to carb load for a half marathon or 10K?
Not the full multi-day version. Races that finish inside your glycogen window — a 10K, and a half for faster finishers — don't drain the tank far enough to need 48 hours of dedicated loading. One carb-forward day and a normal, familiar dinner does it. But the underlying rule holds at every distance: the tank still has to be topped off going in, even when no mid-race fuel is needed — do you need gels for a 5K, 10K, or half marathon walks that logic race by race.
Can you carb load with gels?
Honestly, no — and we make gels. Loading is 500-plus grams of carbs a day; that's the work of meals, done over a table, not pouches. Gels are built for during — fast carbs mid-effort, when chewing and digesting a meal isn't an option. Where a gel genuinely fits into race week: as a top-up, 10 to 15 minutes before the start, so you cross the line with carbs ready to go. After the gun, the usual rhythm takes over — how many gels for a marathon, half, or ultra has the counts.
Race week, with Hüma
The loading belongs to your kitchen; Hüma's job starts when the race does. Race week is simply when to stock the pouches — grab your race-day supply on the same grocery run as the pasta, so packet-pickup week isn't also a scramble for fuel. Let taste lead the pick: each pouch is 24 grams of real-food carbs from brown rice syrup and real fruit purees, with chia, and the flavor you genuinely like is the one you'll take on schedule at mile 18. Not sure where to start? Strawberries is the all-time best-seller. Then finish the plan where the race begins: what to eat the morning of a race carries the last few hours to the gun.
Related guides
- What to eat the night before a race
- What to eat the morning of a race (and how long before)
- How many energy gels for a marathon, half, or ultra?
- How to fuel your first marathon
- Endurance Nutrition 101: the basics of fueling
FAQ
What does carb loading actually do?
It fills your glycogen stores — the carbs your body banks for long efforts — all the way up before a race. A full tank covers roughly 90 minutes to two hours at effort, so a marathon runs better when you start with every gram stored.
How many days before a marathon should you carb load?
The final 36 to 48 hours — one to three days — while your training tapers. Starting a week early doesn't build a bigger tank; your body can't stockpile glycogen that far ahead.
How many carbs should you eat when carb loading?
Roughly 3.5 to 5.5 grams per pound of body weight per day — about 550 to 800 grams for a 150-pound runner. The low end is plenty for most non-elite athletes, and juice or a sports drink is an easy way to close the gap.
Is it normal to gain weight while carb loading?
Yes — expect 1 to 3 pounds. Glycogen is stored with water, so the gain is the load working, and your body draws on that fluid during the race.
Can you carb load with energy gels?
No — loading takes hundreds of grams of carbs a day, which is a job for meals. Gels are built for during the race. The one race-week role for a gel is a top-up 10 to 15 minutes before the start.
