Carb loading, done right
How to top up glycogen before a marathon, century ride or long race — without the bloat.
What carb loading actually does
Your muscles and liver store carbohydrate as glycogen — roughly 400–500g when topped up. During hard endurance efforts you burn through it, and when it runs low you hit the wall: legs heavy, pace collapsing, brain foggy. Carb loading is simply the practice of maximizing those glycogen stores in the days before a long event so you have more fuel to spend.
It matters most for continuous efforts longer than about 90 minutes — marathons, long-course triathlons, century rides, long trail runs. For a 5K or a gym session, it's overkill.
How many carbs, and for how long
The modern protocol is simpler than the old week-long depletion-and-load routines. For the 36–48 hours before your event, aim for 8–12 grams of carbohydrate per kilogram of body weight per day. A 70 kg runner targets roughly 560–840g of carbs daily across those two days.
You don't need to train differently or deplete first — just taper your training and raise your carb intake. Use our calculator to get your exact daily target.
- • Marathon / long triathlon: 10–12 g/kg/day, 2 days out
- • Half marathon: 8–10 g/kg/day, 1–2 days out
- • 10K or shorter: normal training intake is plenty
What to actually eat
Hitting 600g+ of carbs is hard if you eat the way most 'clean eating' advice suggests. This is the time to lean on lower-fiber, easy-to-digest, carb-dense foods so you're not uncomfortably full or running to the bathroom on race morning.
Favor white rice, pasta, bread, bananas, dates, potatoes, oats, juice and sports drinks. Pull back on very high-fiber foods, large salads, and heavy fats in the final 24 hours.
The mistakes that ruin race day
Three errors undo most carb loads. First, adding calories from fat instead of carbs — you gain weight without gaining glycogen. Second, eating a giant high-fiber meal the night before and paying for it at the start line. Third, trying brand-new foods. Nothing on race week should be untested.
Frequently asked
Will carb loading make me gain weight?+
You'll gain 1–2 kg, but most of it is water bound to the extra glycogen (about 3g of water per gram of glycogen). It's stored fuel, not fat, and it's working for you on race day.
Do I need to deplete carbs first?+
No. The classic depletion phase is outdated and miserable. Simply taper training and raise carb intake for 1–2 days before — you'll max out glycogen just the same.
How many carbs the morning of?+
1–4 g/kg in the 1–4 hours pre-start, with familiar low-fiber foods like oats, a banana, toast or a bagel.