Running Fuel for Marathoners: How an Ultramarathoner Preps for a Long Run

A man well-stocked with running fuel runs along a road at midday.

Running Fuel for Marathoners: How an Ultramarathoner Preps for a Long Run


Running fuel — the nutrients your body consumes while performing endurance exercise — is a hotly-debated topic in the running world.

Marathons and ultramarathons require tremendous amounts of energy and place enormous stress on the body. From the long training cycle to the main event, running fuel may involve carbohydrate loading (carbo loading), energy gels, and on-the-go snacks. Some runners even use candy or soda!

Because everyone’s mileage varies (yep, we went there), we decided to seek the wisdom and insight of a real-life Forrest Gump: Ultramarathoner David Carder.

Ultramarathoner David Carder, our running fuel expert, runs along I-40 toward California.

Ultramarathoner David Carder

David is a freelance content writer currently living in California’s Sierra Nevada mountains and has been running marathons and ultra marathon endurance events most of his life.

A few years ago, he and a small group of runners ran 2,400 miles of Route 66 from Chicago to the Santa Monica Pier in California in 19 days. To cover the distance on schedule, David ran 50km (31 miles) every day for nearly three weeks.

Here’s what David had to say about fueling for long runs and taking care of your body while training for race day:


Live Run Travel: Thanks for letting us pick your brain today. Why does running fuel seem to be such a difficult subject for marathoners to figure out?

David: Everyone is different. Men and women. Young or old. Everyone has a different disposition when it comes to what is the ideal combination and frequency of fueling when putting out strenuous effort for many hours at a time.

There are some basic parameters that can be followed, but it will involve some trial and error for each individual to find the right mix that allows you to perform your best under those conditions.


Live Run Travel: Let’s start with the basics then: How should people fuel for a marathon, race, or long run?

David: People tend to overdo calories before long runs or a race by carbo-loading the night before. There is only so much glycogen your body can store. The rest can cause your blood sugar levels to rise and crash and make your system feel sluggish the next 12-24 hours. A well-balanced meal of mostly whole foods, some healthy fats, and protein are a good balance to have all your systems working as efficiently as possible.


Live Run Travel: So running fuel isn’t all about the carbs anymore?

David: Calories from healthy fats contain 20 times the energy compared to carbs. Training your body to be more adapted to burning and accessing your fat stores will allow you to be more efficient and reduce the amount of fuel you have to consume during your long runs.


Live Run Travel: So nutrition for runners is more than just a bowl of pasta before race day. Are you saying runners should utilize a Keto diet?

David: I am not advocating a pure Keto diet, although it may work for some people. For many, it will be a modified version of Keto that has you eliminate all processed foods, added and refined sugars, and starches.

Basically, you should be eating as many vegetables as you want, a reasonable amount of protein for your lean body mass, and some healthy fats. The exact balance that is ideal will vary from person to person.

Live Run Travel: That can be hard these days!

David: Basically, if it did not exist as food 150 years ago you probably should not be eating it anytime!


Live Run Travel: That’s a great way to look at it. Eat healthy, clean food every day and have a well-balanced meal the night before. Got it!

What running fuel should we use, and how often should we fuel, before and during our long run/race

David: Before the run starts, try to follow your normal morning routine as much as possible. If you drink coffee or eat a light breakfast, be sure to do that. If you know that will require you to allow some time for a bio break in the bathroom before heading ahead, account for that as well.


Live Run Travel: Great advice. There is not always a bathroom around when nature calls during a run!

David: We have not said much about hydration, but if you have a good habit of maintaining proper hydration on a daily basis you should be going into the long run relatively well hydrated.

For most people, one 16 ounce bottle of fluids per hour is the starting rule of thumb. Do not get behind on hydration. When we are even slightly dehydrated our performance can fall off 10-15%.


Live Run Travel: Are you a fan of sports drinks?

David: Not the ones that contain added sugars or toxic dyes.

The sugars added to these drinks and other types of fuel can cause gastrointestinal distress when your body tries to process them when you are exerting intense levels of physical exercise over an extended period of time.

Stick with cleaner electrolytes like Nuun, Gu or Tailwind.


Live Run Travel: Okay, so a bottle of fluid per hour. What about running fuel or on-the-go food?

David: The average person can only process about 350 calories of food an hour under normal conditions. On a hot day, while working hard on a run, that number can go down.

You may be burning 800-900 calories an hour while running, so you obviously have to get some of those calories from somewhere else to make up the deficit.

This is where our body fat becomes our friend.


Live Run Travel: We knew we were holding onto some of that leftover fat from the holidays for a reason!

David: That’s right! If your run is an hour or less you should be able to complete the run with the hydration strategy we just discussed.

Longer than an hour, and you will need to add some calories each hour. Gels work fine for some people, while some people like whole foods like peanut butter with calories from fats.

I would not recommend more than 150 calories an hour between what is in your fluids and the food you drink. It takes energy to digest calories, so the fewer calories per hour you can maintain, the better.

And taking in a smaller amount of calories will greatly cut down on the chances of an upset stomach and having to make a desperate dive into some bushes along the way.


Live Run Travel: It seems like your tips are geared toward teaching the body to be more energy-efficient. Learning how much running fuel you use — and what type you should use — changes on an individual basis.

David: Exactly! If you are training for a marathon you are logging all your miles, right?

You should also be logging all of your food as well. Every single thing you put in your mouth during the week put in the log.

Once you start writing this down you will begin to make more conscious choices about what you put into your fine-tuned machine as fuel. The cleaner you eat, the better you will perform.


Live Run Travel: Okay: last question. Did you feel like Forrest Gump as you ran across the United States and ended up at the Pacific Ocean?

David: It’s always been one of my favorite movies. The whole experience was a dream come true. If you remember in the movie, the first time he gets to the Pacific, he is standing on the end of the Santa Monica Pier just staring for a minute before he turns around to run all the way back the other way.

I stood in that exact spot after running for 19 days straight. I knew exactly how he felt because all I wanted to do in that moment was turn around and just keep running!


Live Run Travel: Thanks so much for taking the time to share your story and tips for running long!

David: You are most welcome.


Wrapping Up

And there you have it: An ultramarathoner’s advice on running fuel, carbo-loading and everything in between!

Training for a marathon is never easy, and running 19 marathons back-to-back is a surefire way to put your dietary advice to the test!

Certainly, it’s an adventure of a lifetime. If you’re looking for your own running adventure, we can help!

Check out our tour packages and long-distance running advice. It’s the first step (yep, we went there again) toward adding a little wanderlust to your next marathoning event!

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