Marathon Fuelling: What to Eat Before and During

Written by James Frost, founder of Flaming Phoenix. Updated October 2026.

Marathon fuelling means 10 to 12g of carbohydrate per kilogram of body weight a day for the 36 to 48 hours before the race, and 1 to 4g per kilogram at breakfast 1 to 4 hours before the start. During the race, aim for about 60g an hour, up to 90g if your stomach is trained for it.

Those ranges come from the 2016 joint position statement on nutrition and athletic performance of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada, and from Asker Jeukendrup’s 2014 review of carbohydrate during exercise in Sports Medicine. Below, they become food, gel counts and clock times for the spring 2027 races.

What is a good marathon fuelling strategy?

A good marathon fuelling strategy fills your glycogen stores in the two days before, tops them up at breakfast, then feeds you carbohydrate from early in the race at a rate you have practised. That way you do not run short of glycogen, your stored carbohydrate, and hit the wall late on.

The table applies the guidelines to a 60kg and an 80kg runner; carbohydrate during the race does not scale with body weight, Jeukendrup’s review states.

If you take medication to manage your blood sugar, are pregnant, or eat to a diet set by a health professional, run these numbers past them before race week.

How do you carb load for a marathon?

To carb load for a marathon, eat 10 to 12g of carbohydrate per kilogram of body weight a day for the 36 to 48 hours before the start, while tapering your training. The position statement sets that target for any event longer than 90 minutes.

A 60kg runner needs 60 × 10 = 600g to 60 × 12 = 720g a day; an 80kg runner, 800 to 960g. Cooked spaghetti has 31.5g of carbohydrate per 100g in the UK’s CoFID food tables, so 600g from spaghetti alone would mean about 1.9kg of it, and 800g about 2.5kg.

Not every guide asks for that much: Science in Sport’s April 2026 guidance suggests 6 to 10g per kg, lower for first-timers. At 8g per kg, a first load is 480g a day at 60kg and 640g at 80kg; the carb loading calculator works out your own number and an example day of food.

The 2027 TCS London Marathon runs over two days on the same route, so a runner allocated Saturday 24 April starts loading on Thursday morning and a Sunday runner on Friday morning.

What should you eat when carb loading?

Choose foods that are low in fibre and easy to eat in quantity, as the position statement advises for gut comfort. The table gives carbohydrate and calories per portion from CoFID 2021 and the labels for Lucozade Sport and Phoenix Bars.

A 300g plate of pasta is 112g, so a 60kg runner would need more than five a day to reach 600g: spread it across meals and snacks, and drink some of it.

What should you eat the night before a marathon?

The night before a marathon, eat a familiar, low-fibre carbohydrate dinner at your usual time. It is one meal inside the loading days and cannot make up for two days of eating too little.

For example, 300g of cooked white pasta with plain tomato sauce and 100g of white bread is about 158g of carbohydrate (112g plus 46g), roughly a quarter of a 60kg runner’s 600g day. Save creamy sauces and curries for after the race.

What should you eat on marathon morning?

On marathon morning, eat 1 to 4g of carbohydrate per kilogram of body weight 1 to 4 hours before the start, from low-fat, low-fibre foods you have eaten before long runs. The position statement says such food is less likely to upset your stomach.

At 2g per kg about three hours out, that is 120g of carbohydrate at 60kg and 160g at 80kg. The London organisers expect the Saturday race to start at about 09:00 and the Sunday race at about 09:30, so breakfast falls around 06:00 or 06:30; count back from the start time in your own event information. Both breakfasts below use CoFID values and the bar’s label.

A Vanilla Phoenix Bar gives a 60kg runner 1.1g of carbohydrate per kg (66 ÷ 60), the bottom of the range, so treat it as the base of a breakfast. It carries fat and protein too, so I would eat it three hours or more before the start, after trying it before a long run.

Drink as well. The position statement suggests 5 to 10ml of fluid per kg in the 2 to 4 hours before exercise: 300 to 600ml at 60kg and 400 to 800ml at 80kg, with time to pass the excess before you line up.

How many carbs per hour do you need during a marathon?

Most marathon runners should aim for about 60g of carbohydrate an hour, moving towards 90g only if they have practised it on long runs. A 2015 review by Beck and colleagues, adapting Jeukendrup’s guidelines, gives 60g an hour for a marathon-length effort of 2 to 3 hours.

The position statement allows up to 90g an hour beyond about 2.5 to 3 hours, but Jeukendrup notes that a single sugar such as glucose is used at up to about 60g an hour, so more needs a glucose and fructose mix. He adds that a 5-hour marathon runner is unlikely to need 90g an hour, which could exceed all the carbohydrate they burn at that pace, and that newer runners may need less than his figures for well-trained athletes.

How many gels for a 3, 4 or 5 hour marathon?

A marathon takes between 5 and 13 gels if gels supply all of your carbohydrate, depending on finish time and gel size. The table multiplies the hourly target by the finish time and divides by one gel’s carbohydrate: 23g for a HIGH5 Energy Gel Aqua, handed out at Brighton and Manchester, or 40g for an SiS Beta Fuel gel, rounded to whole gels.

Sports drink brings the count down. Lucozade Sport’s label gives 6.3g of carbohydrate per 100ml, so 250ml at each of London’s four Lucozade Sport stations adds about 63g, almost three of the smaller gels. At 60g an hour, a 23g gel goes in about every 23 minutes and a 40g gel every 40 minutes. Thirteen small gels is a lot of sweet liquid for a 5-hour runner, so mix in drink and something you can chew. The running calorie calculator shows what the 42.2km costs you in calories.

How much should you drink during a marathon?

Most marathon runners do well on 0.4 to 0.8 litres of fluid an hour, adjusted to their own sweat rate, which the position statement says runs from 0.3 to 2.4 litres an hour.

To estimate yours, weigh yourself without clothes before and after a long run at race pace; each kilogram lost is about a litre of sweat. A 60kg runner who finishes a 2-hour run at 59.2kg after drinking 400ml has lost about 0.8 litres plus the 0.4 they drank: 1.2 litres in 2 hours, or 0.6 litres an hour. Allow for any toilet stop.

The statement advises sodium for exercise longer than 2 hours, sweat rates above 1.2 litres an hour or salty sweat. Sweat averages about 1g of sodium per litre, though it varies widely, so on a warm day carry an electrolyte drink you have trained with.

Drinking too much is the rarer mistake but the more dangerous one. The statement names drinking more than you sweat as the main cause of low blood sodium during exercise, with recreational runners and women at greater risk; bloating, weight gain, nausea, headache and confusion need prompt medical attention. With water every two miles in London’s second half, you do not need a bottle at every station.

What drinks and gels are on the course at UK marathons in 2027?

London, Brighton and Manchester hand out water regularly but gels at only two or three points each, so carry most of your own carbohydrate. I checked each official page in October 2026; read your participant guide in race week in case anything changes.

At London, 250ml from each Lucozade Sport station gives about 63g plus two gels, against 240g for a 4-hour runner at 60g an hour. Brighton’s HIGH5 Zero is sold as a sugar-free electrolyte drink with zero calories, so the carbohydrate on offer is the two gels: 46g. Manchester’s three gel stations give 69g, and the race advises bringing what you have trained with. London also has water refill points at miles 5, 10, 14, 17 and 20 for bottle belts and hydration packs.

Where does a Phoenix Bar fit in marathon fuelling?

I make Phoenix Bars, so read this as the maker’s view. For most marathon runners, a bar belongs in the days and hours before the race, and seldom in the race itself.

• Loading days. Up to 557 calories and up to 66g of carbohydrate in only 120g, about a tenth of a 60kg runner’s 600g day, and it stirs into hot water as high calorie porridge when you are tired of pasta. It also carries fat and up to 19g of protein, so it goes alongside rice, bread and juice, not in place of them.
• Race morning. Eat it three hours or more before the start, as in the 80kg breakfast above. Justin Mullis did a version of this at the Sydney Marathon: “I split my Phoenix Bar in half and I had one section before the race and carried the other half with me.”
• During the race. A whole bar is a lot at marathon pace. Yuko, who runs full marathons, wrote that “the whole bar was probably a little too much to eat during the race” and ate about half of it bit by bit. A third of a bar has 20 to 22g of carbohydrate, about one small gel, so a few pieces can stand in for a gel or two if you are out for five hours and gels stop going down; try it on a long run first.

These high calorie bars are more at home on days far longer than a marathon. If an ultra is next, my guide to first ultramarathon nutrition starts where this page stops.

How do you practise marathon fuelling in training?

Practise the whole plan on long runs at marathon pace: the same breakfast at the same interval, the same gels and drinks, at your race rate. Jeukendrup recommends this; in animal studies the gut’s carbohydrate transporters increase on a high-carbohydrate diet, and athletes report absorbing more with practice.

• Start near the bottom of the 30 to 60g range and add a little on each long run.
• If you will use the course supplies, train with them: Lucozade Sport and its gels for London, HIGH5 gels for Brighton and Manchester.
• Rehearse the clock: for a London Sunday start at about 09:30, eat at 06:30 before a long run that starts at 09:30.
• If gels are hard to swallow, try the London Marathon’s gel advice: a third of the gel, some water, then the next third.

If higher intakes upset your stomach, my guide to gut training sets out a step-by-step protocol; it is written for ultras, and the same steps suit a marathon build.

What are the most common marathon fuelling mistakes?

• Treating the pasta dinner as the carb load. A 300g plate is 112g of carbohydrate, against 600 to 960g a day for a 60 to 80kg runner.
• Counting on the course. London and Brighton have gels at only two points each, and Brighton’s sports drink has no calories.
• Starting late. The London Marathon’s gel advice is to take something within the first hour.
• Drinking at every station whatever the weather.
• Trying something new on the day: a gel from the expo, a different breakfast, a first coffee.

Frequently asked questions

When should you take your first gel in a marathon?

Take your first gel or sports drink within the first hour. The London Marathon’s gel advice, written with Lucozade’s sport scientist, suggests starting within the first hour and then every 30 to 40 minutes. To reach 60g an hour with 23g gels you need one about every 23 minutes, so fill the gaps with sports drink.

Is coffee a good idea before a marathon?

Coffee is fine before a marathon if you already drink it before long runs. The International Society of Sports Nutrition’s 2021 position stand found caffeine consistently improves performance at 3 to 6mg per kg, most often taken 60 minutes beforehand: 180 to 360mg for a 60kg runner. Very high doses, around 9mg per kg, bring frequent side effects.

Can you fuel a marathon with real food instead of gels?

Yes. Jeukendrup’s review says carbohydrate during exercise can come from liquid, semi-solid or solid food, so the limit is what you can chew and swallow at race pace. A peeled banana has about 20g of carbohydrate per 100g in CoFID, close to one small gel. My guide to energy gel alternatives compares more options.

Do slower runners need to carb load?

Yes. The loading guideline covers any event longer than 90 minutes, and a 5-hour marathon is more than three times that. Slower runners can usually take less carbohydrate per hour during the race, because Jeukendrup notes that lower intensity burns less of it, but they still start on the glycogen stored in the two days before.

What should you eat the week before a marathon?

Eat your normal training diet for most of the week and save the big increase for the last 36 to 48 hours. The position statement says loading works by extending a carbohydrate-rich diet while tapering training over about 48 hours, so a full week of extra pasta is not needed. Avoid anything new or spicy, as Science in Sport advises.

Sources: Joint position statement on nutrition and athletic performance (2016); Jeukendrup, Sports Medicine (2014); Beck and colleagues (2015); ISSN caffeine position stand (2021); Science in Sport (2026); CoFID 2021; London Marathon course; London 2027 Double FAQs; London Marathon gel advice; Brighton Marathon course; Brighton Marathon 2027; Manchester Marathon nutrition; HIGH5 gel label; HIGH5 Zero label; Lucozade Sport label; SiS Beta Fuel gel.