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How to Consume More Calories During Marathon or Trail Running Races

Typically our body can only absorb 30-60 grams of carbohydrates per hour during an endurance event.

Do you know there are ways to increase your carbohydrate consumption beyond these values?

While reading Vegetarian Sports Nutrition by D. Enette Larson-Meyer, PhD, RD I learned of some very interesting scientific studies that may allow you to consume up to 100 grams of carbohydrates per hour. This is no small increase. How about a 66% increase!

Two of the studies Larson-Meyer referred to include:

How is this possible?

Well apparently the intestines have a limited carbohydrate/sugar absorption rate per sugar type (maltodextrin/starch, fructose, glucose, sucrose, etc). So this means if you consume only one sugar source, such as fructose, you will only be able to absorb 30-60 grams per hour, but if you include multiple carbohydrate/sugar sources into your fueling strategy your total carbohydrate absorption rate increases therefore more fuel can be consumed.

Who may benefit from this?

Each person has to figure out their own caloric needs through trial and error but marathoners and ultra (50k, 50 mile, 100 mile, etc) road and trail runners may benefit from higher carbohydrate consumption. The longer (slower) the event, the more likely one could increase the mixed-carbohydrate fuel sources and benefit from it.

On the flip side, the greater the intensity/heart rate, the less calories one can consume.  Also, the act of running may reduce the amount of calories one can consume. The story is never completely black and white when we are talking about individual human bodies.

This approach is something that would definitely be beneficial to try out in training first to see how your body handles the various sugar sources and caloric increase!

Just because you can increase your carbohydrate consumption doesn’t mean you need to. You must decide when and where this option would be applicable for you. Just being aware of this information may provide an opportunity to dig yourself out of a hole and keep you moving forward during some long course endurance events in the future.

Sports nutrition maltodextrin source

Hammer Nutrition (15% off first order) makes some great maltodextrin sports nutrition products that include both gel (Hammer Gel) and powder products (HEED, Perpetuem(an aquired taste) ). I have personally used them for many years and like them because they don’t have any junk in them. The products also do not include commercial-grade sugars. These sugars are not good for your general health so I prefer not to consume them in endurance sports products.

I have taken Coke during the later stages of a race and it has brought me back to life but I wouldn’t recommend general processed sugar products as part of a standard fueling strategy.

Do you know of any other really clean endurance sports fuels without the simple sugars?

Other sugar sources

Various processed sugar products is one way to include a spectrum of sugar types but as mentioned above, it is not beneficial to general health.

Another area to explore are natural sugar sources such as dried fruit, fresh fruit, and fruit juices. These natural sugar sources contain various ratios of fructose, glucose, sucrose, maltose, and starch within a single item. From all of the fruit items I have looked at, they all contain at least two carbohydrate sources.


Many trail running, marathon, and long course triathlon events include various fruit choices at their aid stations so becoming familiar with them can only help you out whether you plan to use fruit or not. That one day may come when your current fuel source isn’t working for you during a race and this knowledge may prove useful. Just maybe.

Here are a few fruit items and the carbohydrate sources in each. The carbohydrate sources are listed from greatest to least percentage (Gl – Glucose, F – Fructose, Su – Sucrose, M – Maltose, Ga – Galactose, St – Starch).

I personally would look to use fruit sources that had different leading carbohydrate sources. For example, bananas and oranges, grapes and figs, oranges and apricots.

You can check out any other fruit source over at NutritionData by simply entering the item in the search box at the top of the page. It also wouldn’t hurt to become familiar with the carbohydrate content per quantity of fruit for any items you may use in training or a race.

As with all caloric fuel items, you need to drink sufficient water along with the fruit item to aid in absorption. It is no different than if you were taking a gel. I also would try and chew the appropriate fruit item fairly well to help aid in the digestion.


Now go out and play. See what works for you during some of those long training runs.

And above all else, have FUN!

Happy Training!

About the author

David Hanenburg David Hanenburg is the passionate dirt-lovin' creator of Endurance Buzz and has been playing in the endurance sports world since 2000 after knockin' the dust off of his Trek 950 hardtail thanks to a friend asking to go ride some local dirt. In 2007 he ran his first ultra on the trails and fell in love with the sport and its people. For more information on David's endurance sports journey, check out the About page.

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