First Marathon Fueling Guide: What to Eat Before, During, and After Your Race

You have a training plan. You have new shoes. You have a playlist that could power a rocket. But if you line up for your first marathon without a fueling plan, none of that matters after mile 18.

Fueling is the part of marathon preparation that first-timers most often neglect — and it is the single biggest reason runners hit the wall. Not fitness. Not willpower. Fuel.

The good news: getting your race nutrition right is not complicated. It just needs to be deliberate, personal, and practised. This guide walks you through everything you need to know, from 12 weeks out to the post-race meal you have absolutely earned.

Why fueling matters more than you think

Your body stores roughly 1,500–2,000 calories of glycogen in your muscles and liver. A marathon burns somewhere between 2,200 and 3,500 calories depending on your weight and pace. You can see the problem: you will run out of stored fuel before you reach the finish line.

When your glycogen tanks empty, your brain starts shutting things down. Your legs feel like concrete. Your pace craters. Your mood follows. Runners call this "hitting the wall" or "bonking," and it typically strikes between miles 18 and 22.

The fix is simple in principle: take in carbohydrates during the race so your glycogen never fully depletes. The details — how much, when, and what format — are where most first-timers get lost.

The 12-week fueling timeline

If your fall marathon is 12–16 weeks away, you are in the perfect window to build your nutrition plan alongside your training.

Weeks 12–8: Learn your baseline

This is the phase where you figure out what your body tolerates, not what the internet recommends. Start experimenting with fueling during your long runs.

Try one gel or a serving of chews at the 45-minute mark. See how your stomach responds. Try a different brand the following week. Take notes: what brand, what flavour, how much water you drank with it, how your stomach felt 20 minutes later.

The goal here is not performance. It is data collection.

Weeks 8–4: Lock in your products and timing

By now you should know which fuel sources agree with your stomach and which ones do not. Narrow your options to one or two products and start using them consistently on every long run.

Begin practising your full race-day timing protocol. Take your first fuel at 45 minutes, then every 20–30 minutes after that. Match the conditions as closely as you can: same products, same hydration, same pre-run breakfast.

Weeks 4–1: Dress rehearsal

Your final two or three long runs are full simulations. Eat your race morning breakfast at the right time. Use your exact race products. Carry them the way you plan to carry them on race day. If anything goes wrong, you still have time to adjust.

The golden rule of race nutrition: nothing new on race day. Every gel, every drink, every pre-race meal should be something your body has already approved.

How much to eat during the race

This is the question every first-timer Googles, and the answer you will find most often — "30–60g of carbs per hour" — is technically correct but practically useless without context.

Here is how to think about it as a beginner.

If you are finishing in 4–5 hours

You are on your feet for a long time, which means you will burn through more total glycogen than a faster runner. Aim for 40–60g of carbs per hour after the first 45 minutes. That is roughly one gel every 25–30 minutes, or two gels per hour if they are 20–25g each.

Most first-timers need 6–10 gels for a full marathon at this pace. That sounds like a lot because it is. This is why practising during training matters — your gut needs to learn how to absorb fuel while running.

If you are finishing in 3:30–4:00

You can get away with slightly less total fuel because you are on the course for less time, but each hour is more demanding. Target 30–50g of carbs per hour after the first 45 minutes. Five to seven gels across the race is a reasonable starting point.

If you are finishing under 3:30

At faster paces, blood flow diverts away from your gut and toward your working muscles. You may tolerate less fuel per hour even though your burn rate is higher. Start at 30g per hour and increase only if your gut allows it during training.

The maths in plain language

One standard energy gel contains 20–25g of carbohydrates. One serving of energy chews contains roughly the same. A 500ml bottle of sports drink contains 30–40g. Mix and match to hit your hourly target.

The exact amount you need depends on your body weight, your pace, the weather, and your individual metabolism. This is exactly the kind of calculation that a tool like Sweatr does automatically — it takes your Apple Watch or Garmin data, your body weight, and your target pace and builds a gel-by-gel fueling schedule you can follow on race day.

What to eat before the race

The night before

Carbohydrates. Not an absurd amount — you are not carb-loading in one meal. A normal-sized dinner with a carbohydrate base: pasta, rice, potatoes, bread. Avoid anything high in fibre, fat, or spice that might unsettle your stomach overnight.

Do not try a new restaurant. Do not eat that exciting local dish near the race venue. Eat something boring that you know agrees with you.

Race morning (3–4 hours before the start)

Your pre-race breakfast is the last chance to top up liver glycogen, which depletes overnight while you sleep. Aim for 100–150g of carbohydrates, low in fibre and fat.

Good options that work for most runners:

• Two slices of white toast with honey and a banana
• A medium bowl of white rice with a little salt
• A plain bagel with peanut butter and jam
• Porridge made with water, topped with banana and honey

Drink 400–600ml of water with your breakfast. Stop drinking about 90 minutes before the start to give your body time to process the fluid.

30 minutes before the gun

A small top-up: one gel or a few swigs of sports drink. This is not essential for everyone, but many runners find it gives them a smoother first hour.

What to eat during the race

The first 45 minutes

Nothing. Your body has plenty of glycogen to get through the opening miles. Use this time to settle into your pace, find your rhythm, and drink water at the first aid station if you are thirsty.

Miles 7–20: The fueling window

This is where your plan earns its keep. Take your first gel or chews around the 45-minute mark (roughly mile 6 for a 4:30 marathoner, mile 7 for a 3:45 marathoner) and continue every 20–30 minutes.

A few rules that will save your stomach:

Always take gels with water, never with sports drink. A gel plus a sports drink creates a sugar concentration in your stomach that your gut cannot absorb quickly. The result is nausea, bloating, or worse.

Alternate between water and sports drink at aid stations. If you are getting carbohydrates from gels, you only need water to wash them down. If you skip a gel, grab a sports drink instead to keep the carbs coming.

Do not wait until you feel bad to eat. By the time you feel the bonk, it is too late to fix it. Fueling is preventative, not reactive.

Miles 20–26.2: Protect the finish

The last 10K is where fueling failures show up. If you have been consistent from mile 7, your glycogen stores should be holding. Keep taking gels every 25–30 minutes. If your stomach is rebelling, switch to sports drink — it is easier to absorb than solid or semi-solid fuel.

If you feel a sudden energy crash, take a gel with caffeine if you have one. Caffeine does not give you more glycogen, but it reduces the perception of effort and can buy you 20–30 minutes of clearer thinking and stronger legs.

Hydration during the race

Hydration and fueling work together, but they are not the same thing.

How much to drink

A general starting point is 400–800ml per hour, but the actual amount depends on your sweat rate, the temperature, and the humidity. A 60kg runner on a cool morning needs far less than a 90kg runner in July heat.

The simplest way to find your personal sweat rate: weigh yourself before and after a one-hour training run (no fuel, minimal water). Every kilogram you lose is roughly one litre of sweat.

What to drink

Water at every other aid station. Sports drink at the ones in between. If you are using gels, lean toward water so you are not double-dosing on sugar.

Watch for overhydration

Drinking too much is a real risk, especially for slower runners who spend more time on the course and hit more aid stations. Hyponatremia — dangerously low blood sodium from excessive water intake — is more common than dehydration at the back of the pack. If you are gaining weight during the race or your fingers are swelling, you are drinking too much.

What to eat after the race

Your muscles are primed to absorb nutrients in the 30–60 minutes after you finish. This is not the time for discipline — it is the time for recovery.

Within 30 minutes

A recovery drink or snack with a 3:1 or 4:1 ratio of carbohydrates to protein. Chocolate milk is the cliché because it works. A banana and a handful of pretzels. Whatever the race organisers hand you at the finish line.

Within 2 hours

A proper meal. Carbohydrates to replenish glycogen, protein to repair muscle damage, and salt to replace what you sweated out. A burger, a burrito, pasta with meat sauce — this is the one meal where "whatever sounds good" is genuinely solid nutritional advice.

The next 24 hours

Keep eating. Your body is rebuilding. Do not restrict calories the day after a marathon. Drink plenty of fluids with electrolytes. Sleep as much as you can.

Common first-timer mistakes

Skipping fuel because "I ate a big breakfast." Your pre-race breakfast tops up your liver glycogen, not your muscle glycogen. You still need to eat during the race.

Trying a new gel on race morning. If you have never tested it in training, your stomach might reject it at mile 14. Only use products your body has approved.

Waiting until you feel hungry. Hunger is not a reliable signal during exercise. By the time you feel it, your glycogen is already critically low.

Copying a fast runner's plan. A sub-3 marathoner's fueling plan is built for a different metabolic demand than a 4:30 marathoner's. Your plan should match your pace and your body, not someone else's.

Grabbing whatever is at the aid station. Know in advance what the race is offering. If it is a brand you have not tested, bring your own.

Let your data build the plan

The ranges in this guide are starting points. Your actual fueling needs depend on your body weight, your sweat rate, your target pace, and the weather on race day. These are variables, and variables deserve a personalised answer.

Sweatr connects to your Apple Watch, Garmin, or Strava data to calculate your personal carbohydrate and fluid needs for every long run and race. Instead of wondering whether you need six gels or nine, you get a schedule that is built for your body and your race. It takes the guesswork out of the one part of marathon preparation that most first-timers leave to chance.

Your training plan tells you how far to run. Sweatr tells you how to fuel the distance.