Why is the old 7-day carb load obsolete?

Studies since the early 2000s show trained athletes saturate glycogen in 24-36 hours of high-carb intake, no depletion phase needed. The depletion phase makes athletes feel terrible and provides no advantage.

How much weight will I gain from carb loading?

2-4 pounds of water weight. Glycogen binds ~3 g water per g of carbohydrate. That's a feature, not a bug — the stored water helps with hydration during long races.

What should I eat to carb-load?

Low-fibre, simple carbs: white rice, white bread, bagels, pasta, pretzels, sports drinks, bananas, oatmeal, pancakes, rice cakes, honey, maple syrup. Avoid beans, lentils, whole grains, salads, broccoli.

Do I need to carb-load for a half-marathon?

Marginal benefit. A half-marathon depletes glycogen but doesn't exhaust it for most runners. A carb-forward day before is sufficient for most; full loading is unnecessary and adds GI risk.

Can I carb-load on a gluten-free diet?

Yes. White rice, potatoes, corn tortillas, gluten-free oats, bananas, honey, and rice cakes all work. The protocol doesn't require wheat.

Can I carb-load as a vegan?

Easily. Most carb-loading foods are already vegan: rice, pasta, bagels, pretzels, bananas, sports drinks, maple syrup. Skip beans and lentils during the 36-hour window to control fibre.

What happens if I don't carb-load?

For races under 90 minutes, nothing meaningful. For marathons and longer, you'll start with ~400 g of glycogen instead of 700 g, which usually means a harder last 10K. Under-loading is not a disaster; it's a handicap.

Carb Loading Explained (2026): The Modern 2-3 Day Protocol

Q: How do I carb-load for a marathon?

10-12 g of carbohydrate per kg body weight per day for 24-36 hours before the race. Low-fibre sources. Keep protein normal, reduce fat slightly.

Quick answer

Modern carb loading: 10-12 g of carbs per kg of body weight per day, for 24-36 hours before the race. Low-fibre sources. Expect 2-4 lb of water weight gain from glycogen storage — that's the point. The old 7-day depletion-load is obsolete.

A full glycogen store is roughly 400-500 g of carbohydrate in muscles and 80-100 g in the liver. At marathon pace, a 70 kg runner burns about 350-400 g of carbs across 26.2 miles. Start depleted and you're handing yourself a bonk at mile 20.

The question is how to start the race with full stores. The answer used to be a seven-day process. In 2026, it's a weekend.

How we got here

The original protocol (1960s-70s) had athletes do a long depleting run 6-7 days out, then eat low-carb for 3 days, then switch to high-carb for 3 days. The depletion phase supposedly made muscles "store more" when carbs came back in. It also made athletes miserable — low energy, bad sleep, poor workouts — during a critical week.

Research since the early 2000s, particularly Bussau et al. (2002) and Tarnopolsky et al. (2005), showed trained athletes fully saturate glycogen with 24-36 hours of high-carb intake, no depletion needed. The old protocol got quietly retired in serious coaching, though it still shows up in old marathon books.

The modern protocol

Days 7-3 before race: eat normally. Protein, carbs, fat at usual ratios. You're tapering mileage, so total calories drop slightly. Nothing unusual.
Days 2-1 (24-36 hours out): shift to 10-12 g/kg/day of carbs. For a 70 kg runner, that's 700-840 g of carbohydrate. Low fibre.
Night before race: moderate dinner at 6-7 pm. Most of the load is already in.
Race morning: 1-2 g/kg breakfast 3-4 hours before start.

What 10-12 g/kg actually looks like

Hitting 700-840 g of carbs is harder than runners expect. A full cup of cooked pasta has about 45 g of carbs. A bagel has 50-55 g. A banana has 25 g. You need to eat a lot.

A sample load day for a 70 kg runner:

Meal	Example	Carbs
Breakfast	Oatmeal (large bowl) + banana + honey + toast with jam + orange juice	~140 g
Mid-morning	Bagel with honey + sports drink 500 mL	~85 g
Lunch	White rice + grilled chicken + bread + apple	~140 g
Afternoon 1	Pretzels + sports drink	~90 g
Afternoon 2	Rice cakes + jam	~75 g
Dinner	Pasta with olive oil + bread + lemonade	~150 g
Evening	White toast with honey + small glass of juice	~60 g
Total		~740 g

Low-fibre, not no-fibre

The reason to go low-fibre is GI residence time. Fibre stays in the gut 24-30 hours. If you're loading two days out and eating lentils, half of that lentil meal is still in your colon at the gun. That's how mile 13 ends up being a porta-potty.

Choose "beige carbs" for the load window:

White rice, white bread, bagels, white pasta
Pretzels, rice cakes, crackers
Pancakes, waffles
Bananas (ripe, yellow/brown)
Honey, maple syrup, jam
Sports drink, maltodextrin mix, fruit juice
Oatmeal (rolled, not steel-cut)
Potatoes (peeled)

Skip during the 36-hour window:

Beans, lentils, chickpeas
Raw salads, broccoli, cauliflower
Whole-grain everything (use white during load)
Bran cereals
Apples with skin (ok peeled, but not necessary)
Dairy if you're lactose-sensitive (add GI risk)
Anything new to you

The water weight is intentional

Glycogen binds roughly 3 g of water per g of carbohydrate. If you add 300 g of glycogen to your muscles and liver during loading, you also store about 900 g of water. That's the 2-4 lb "sudden weight gain" some runners panic about the morning of the race.

This water is useful. It's the reserve that helps with cooling and hydration during a long race. You don't want to avoid it. Don't cut water intake to "avoid the bloat."

Modifications

For shorter races

Half-marathon: a carb-forward day two days out is sufficient for most runners. 10K and under: don't need any special loading beyond a normal pre-race dinner.

For ultras

Most ultra-runners do a slightly milder 3-day version at 8-10 g/kg/day for 48-72 hours. Reason: the race is long enough that in-race fueling matters more than starting glycogen, and the milder load causes less GI discomfort on race morning.

For gluten-free runners

Same protocol, different foods. White rice, corn tortillas, potatoes, gluten-free oats, gluten-free pasta, bananas, honey, fruit juice, rice cakes.

For diabetics

Work with your endocrinologist. The protocol as written will spike blood sugar; insulin dosing and timing need adjustment. Not a DIY situation.

Common mistakes

Front-loading too early. Eating 800 g of carbs on Thursday for a Sunday race stores poorly and adds GI risk.
High fibre during the load. Classic "bean chili because it's carb-heavy." Bad idea.
Alcohol at the expo dinner. Dehydrating, disrupts sleep, and displaces useful calories.
Panicking about weight gain. 3 lb of water is the plan working. Don't restrict morning-of fluids to "lose the bloat."
Trying new foods. Never. Everything on your load plate should have been eaten before a long run at least twice.

What carb loading won't do

It won't make a slow runner fast. It won't replace proper training. It won't compensate for bad pacing or missed long runs. What it does is take a finishable race and make the last 10K less awful — potentially worth several minutes for a marathoner, potentially the difference between finishing and DNF for a first-timer.

Marathon Nutrition Guide — the full race-day playbook
Marathon Fueling Calculator — in-race targets
High-Mileage Training Nutrition — daily baseline
Gels vs Real Food — in-race options