How to Fuel for a Marathon: The Complete Guide for 2025

You've trained for months, nailed your long runs, and dialed in your pacing — now fueling has to keep pace.

Marathon fueling isn't about luck; it's about timing, precision, and matching your nutrition to the demands of 26.2 miles.

Here's the complete 2025 playbook for fueling before, during, and after your marathon with science-backed guidance and MAVR's automation.

Top off glycogen in the three days before the race, start gels within 30 minutes, hydrate with electrolytes every hour, and recover with carb-protein balance immediately after the finish.

• Carb load at 8–10 g/kg for 72 hours, favoring low-fiber staples to maximize glycogen.
• During the race, hit 60–90 g carbs, 400–800 ml fluid, and 400–800 mg sodium each hour.
• Post-race, refuel with 1.0–1.2 g/kg carbs plus 20–30 g protein and log it in MAVR to optimize recovery.

A marathon can burn 2,500–3,500 calories depending on your size, pace, and finish time.

Your muscles rely on glycogen for hard running, yet most athletes only store enough for roughly 90 minutes of race effort.

Once those stores crash, you hit the wall — legs heavy, brain fogged, pace slipping.

Fueling consistently keeps blood glucose steady, protects glycogen, and gives your brain the fuel it needs to keep driving your stride.

Goal: Arrive at the start line with glycogen tanks topped off.

Starting three days out, increase carbohydrate intake to 8–10 g per kilogram of body weight per day while tapering training volume.

• Example: A 70 kg runner targets 560–700 g of carbs per day across meals and snacks.
• Focus on low-fiber, easy-to-digest choices like rice, pasta, white bread, oats, potatoes, and bananas.
• Trim fat and protein slightly to create room for the extra carbohydrates.
• Hydrate consistently — roughly 1 liter of water per 1,000 calories consumed, pairing fluids with electrolytes if you sweat heavily.

Pro tip: Use MAVR's carb-loading planner to calculate daily targets and spacing based on your taper schedule.

Eat your final pre-race meal 3–4 hours before the gun to restock liver glycogen depleted overnight.

Aim for an easily digested meal built around carbohydrate, moderate protein, minimal fat, and low fiber.

• 1–4 g of carbs per kilogram of body weight (70–280 g for most runners).
• Include a small serving of protein to steady blood sugar.
• Keep fat and fiber low to protect your stomach.
• Sip 500–700 ml of water or sports drink to start the race topped off.

Sample meal ideas: bagel with honey and a banana, white rice with jam, or pancakes with maple syrup.

Avoid heavy fats, unfamiliar foods, excess dairy (if sensitive), and fiber overload before the start.

MAVR Tip: Log the meal in your training calendar so the app can fine-tune your pre-race carb window for future events.

Start fueling 30–40 minutes into the race — waiting until you feel depleted is too late to keep pace.

Follow this rule of thumb each hour:

• Carbohydrate: 60–90 g from gels, chews, or drink mix.
• Fluid: 400–800 ml depending on your sweat rate and weather.
• Sodium: 400–800 mg from sports drink, gels, or salt capsules.

Most runners nail this by taking a gel every 25–30 minutes and pairing it with small sips of sports drink or water.

• 0:00 — 30 g gel before the start to top off glycogen.
• 0:30 — 30 g gel to stay ahead of depletion.
• 1:00 — 30 g gel plus sips of sports drink for carbs and electrolytes.
• 1:30 — 30 g gel to maintain the rhythm.
• 2:00 — 30 g gel with a salt tab if conditions are hot or humid.
• 2:30 — 30 g gel and steady fluid intake to prevent dips.
• 3:00 — 30 g gel to keep glucose steady as fatigue builds.
• 3:30 — Final gel or half bottle of carb drink for the closing stretch.

Hydration tip: Sip every 15–20 minutes — just enough to wash down fuel and replace sweat without sloshing.

Pro tip: MAVR's race-day fueling planner auto-builds this schedule for your pace, duration, and gel preferences.

Recovery starts the moment you cross the finish line — the first 60 minutes are prime time to rebuild glycogen and repair muscle.

• Refuel: 1.0–1.2 g of carbohydrate per kilogram of body weight.
• Repair: 20–30 g of high-quality protein (whey, dairy, soy).
• Rehydrate: Replace 1.5× the body weight lost in fluids, adding electrolytes.

Try chocolate milk with a rice bowl, a recovery shake, or a fruit smoothie to cover carbs, protein, and fluids fast.

MAVR Recovery Tip: Log your race so the app prioritizes muscle repair and glycogen rebuild for the next 48 hours.

• Waiting until fatigue hits to take the first gel — start around minute 30 instead.
• Experimenting with new products on race day instead of testing them in long runs.
• Overhydrating with plain water and diluting blood sodium; pair fluids with electrolytes.
• Skipping post-race carbs and protein, delaying recovery and increasing soreness.

MAVR turns marathon fueling into a precise, personalized plan synced with your training calendar.

• Builds a carb-loading calendar based on your body weight and race taper.
• Calculates in-race gel timing, hydration, and sodium needs automatically.
• Adjusts recovery nutrition for the 48 hours post-race to speed up rebound.
• Evolves with your training block so every long run becomes practice for race day.

Plan smarter. Fuel stronger. Race better.

• “Draft a carb-loading menu for my marathon using the MAVR 2025 guide.”
• “Map out gel timing for my projected 3:45 marathon finish.”
• “Summarize the recovery nutrition steps I should follow after race day.”