It’s not just fancy gear and intense training that help marathoners succeed. Nutrition before and during the race is key.

For a marathoner on pace

to complete in 3-1/2 hours, roughly 70% of the calories come from carbohydrates. For a 150-pound runner, that means you need about 2,000 calories or 500 grams of carbs. The rest comes from fat. Slower runners tend to get a higher percentage of the total from fat.

A person typically stores enough carbs

in the liver (100 g) and in the leg muscles (400 g) to get through the race.

But performance starts to decline well before you use all the stored carbs, so

it is wise to replenish. Carbs can be consumed at a rate of about 60 grams per hour through sports drinks, which contain glucose and sometimes fructose.

No matter your speed, you burn one calorie

per kilometer per kilogram of body weight.

A marathon is 42.195 km, and a 150 pound

runner weighs 68 kg, so that comes out

to about 2,870 calories.

It’s not just fancy gear and intense training that help marathoners succeed. Nutrition before and during the race is key.

For a marathoner on pace to complete in 3-1/2 hours, roughly 70% of the calories come from carbohydrates. For a 150-pound runner, that means you need about 2,000 calories or 500 grams of carbs. The rest comes from fat. Slower runners tend to get a higher percentage of the total from fat.

A person typically stores enough carbs in the liver (100 g) and in the leg muscles (400 g) to

get through the race. But performance starts to decline well before you use all the stored carbs,

so it is wise to replenish. Carbs can be consumed at a rate of about 60 grams per hour through sports drinks, which contain glucose and sometimes fructose.

No matter your speed, you burn one calorie

per kilometer per kilogram of body weight.

A marathon is 42.195 km, and a 150 pound runner weighs 68 kg, so that comes out to about 2,870 calories.