Eat On The Run: Nutrition Basics For Trail Running

I remember the first time I took someone else’s advice about eating on the run. I was preparing to run my first 50k and I was scared about my lack of a nutrition plan. I had done a lot of long-run training and never experienced the ‘wall’ that so many runners talk about. A very experienced ultrarunning coworker scared me right into following his nutrition plan for my 50k. I ended up running a strong first half but shortly after experienced the discomfort and performance decline from a distended stomach and puke spewing out of me during the second half of the race. I should have known better than to change things so drastically on race day and to instead stick to what had been working for me, but like so many beginners to the sport, I trusted that someone more experienced knew more about what was good for me than I knew.

If you are like I once was and feeling overwhelmed by all the options and choices of what to eat and how often to eat it when you are running, this article will introduce you to the basics of taking in calories via carbohydrates while running, a fairly simple way of maintaining good energy and a content digestive tract. The information in this article is designed for anyone tackling runs of two to four hours at an effort that will leave you tired afterward. Beyond four-hour runs or for very easy long runs, your nutritional needs will likely change. Just remember, though, that there is no one-size-fits-all standard for endurance-running nutrition. We are all unique in our nutrition needs during long runs and races, and you practicing will hopefully make perfect for you. So, what I’m saying is, take the information from this article, do your own experiments, learn and read more, and find out what does and doesn’t work for you.

Jim Walmsley - 2016 Lake Sonoma 50 Mile

Jim Walmsley fueling on the run at the 2016 Lake Sonoma 50 Mile. Photo: iRunFar/Meghan Hicks

The body uses its stored carbohydrates as well as some of its stored fat to fuel running. (The body also uses its stored protein to fuel running, but we won’t detail this in this article.) The ratio of stored carbohydrates and fats you can burn while running depends on a number of factors, most importantly your effort. No matter what speed you run, there is a limited supply of accessible carbohydrates in the body that can be used to fuel running, what amounts to about 90 minutes of running a decent effort for most people. Beyond that and if you don’t feed yourself more carbohydrates, the body must use predominantly stored fat as fuel. This requires either a rigorous adaptation process in order to run at similar paces (that will not be discussed in the balance of this article because of its complexity) or for those not adapted to fat utilization during running, a big slowdown in pace. Slowing down isn’t ideal, so ingesting more carbohydrates for the body to convert to fuel will help you maintain pace and feel energetic. In doing this, your body will continue to burn the carbohydrates you’re fueling with and some stored fat as fuel as you continue to run.

In short, if your run is 90 minutes or shorter, you will be able to replenish your nutritional needs after the run. However, if you are running longer than that at a meaningful effort, plan to intake some calories while running.

The average runner’s stomach can effectively digest a maximum of 150 to 300 calories per hour of certain types of carbohydrates, and this is dependent upon your effort, your body mass, the type of carbohydrate, the climate, and more. The average runner will burn somewhere between 600 to 1,000 calories an hour. This measurement also varies widely due to factors such as your pace, your body mass, the terrain, and more. This works out to a caloric deficit on long runs and that’s alright. The stomach cannot digest an equitable amount of calories to what you are burning.

The goal in this case, however, is to provide it with just enough calories via carbohydrates to help you perform your best. You might hear some runners talk about walking into aid stations and using them as an all-you-can-eat buffet. Indeed, it can be fun and delicious to eat on the run! But putting in more calories than you can digest or the kinds of calories that are hard to digest can make running uncomfortable or disastrous—like my first 50k! You will want to start ingesting these calories no later than 45 minutes into your run and continue to fuel with about 100 calories at regular intervals of around 20 to 30 minutes.

Maltodextrin and fructose are the types of carbohydrates you should aim to fuel with as you are getting started with using carbohydrates as running fuel. Consuming both types of carbohydrate at the same time allows your stomach to absorb more carbohydrates than consuming a single form. When you are reading the ingredient list on your endurance-running nutrition product labels, look for both types of carbohydrate. Some runners have success by consuming small amounts of other kinds of carbohydrates on longer runs (like ones in the four-hour-plus range), too.

As you start your experimentation, keep a food log as part of your training log. Track the amounts and ratios of maltodextrin, fructose, and any other kinds of carbohydrates you ingest during a long run. Many runners will feel better on one form of carbohydrate or the other and sometimes a single brand or flavor will cause indigestion and discomfort. Looking back on your training log for those patterns can significantly reduce the amount of time you spend feeling uncomfortable or changing your long-run plans due to stomach issues. It might help to note how you felt during the run—digestively and energetically—as well as what the weather conditions were like.

Some runners feel better when they also consume a bit of protein—via amino acids—while running, especially during and after long runs. Many endurance-running nutrition products contain amino acids. Be sure to track this in your food log, too, to see how it makes you feel.

Ingesting fat is recommended only if the athlete is running at a very low intensity (unless, as mentioned, the athlete has adapted to the process of using fat for running at higher speeds, which this article doesn’t address), and this is not likely during runs shorter than four hours. Most endurance-running nutrition products do not contain fat.

There are several kinds of substances that you can eat and drink to ingest calories while on the run:

Gels and Gummies/Chews

These are the most common delivery methods for calories. These single-serve packets contain a gel-like substance or very-easy-to-chew blocks. Generally, you take the gels in two or three swallows and the chews require mild chewing before swallowing. Each packet contains about 100 calories (although that can vary, so check the label) so you would want to plan to take 1.5 to three packets for every hour you are running. These products may also boast about the extras they contain such as electrolytes, caffeine, and amino acids.

Energy gels and chews

Examples of gels and chews. Photo: iRunFar/Meghan Hicks

Solids Like Bars and Waffles

On basic premise, these are solids that contain more than maltodextrin and fructose. What is added can run the gamut from other simple carbohydrates, to complex carbohydrates, to fats, to protein, and more. These are more appealing to me the longer I am out. Taking eight gels can feel monotonous and eating something chewable intermittently gives my brain a little boost. Do use care with what is in the product and begin with the simplest ingredient lists first. Like with gels and gummies, you will find some of these also contain extras like electrolytes, caffeine, and amino acids.


Many brands produce a powdered form of energy that is designed to be added to your water. Follow the mixing instructions on the product label, as each product’s serving size is made to match the number of calories average runners can absorb per unit of liquid. With experience, you may be able to dilute or concentrate your solution of powder to water based upon how much you drink, your exertion levels, the weather, and more.

You should know that relying solely on enhanced water for your nutrition has pros and cons. On the plus side, ingesting calories every time you drink can give you a steady stream of calories without having to carry anything extra or make any extra effort. If you are ingesting a more solid form of calories like gel or a bar, you can supplement with liquids containing calories and get even more calories without extra effort. On the down side, you may not drink enough in an hour to ingest enough calories and would definitely need to supplement with solids. Additionally, sometimes it is nice to drink just plain water. With all the flavors and sweetness in gels, bars, and other endurance-running nutrition products, drinking something with more flavor can become a challenge, which would then affect your performance due to dehydration. Bottom line, if you plan to add calories to your water, plan to have supplemental fuel as well as plain water with you in addition until you know if this kind of calorie intake works for you.

Real Food

Yes, it’s possible to eat real food while running. I know people who eat dehydrated berries, smashed berries, peanut butter and jelly sandwiches, bananas, potatoes, sweet potatoes, rice cakes, and a variety of other real food while running. The plus side is that you get to eat real food! The down side is that it can be bulky to carry plus you will generally ingest some amount of fiber. As you may have experienced, running has a way of shaking your digestive system clean. Fiber can have a way of enhancing that effect, which is why most endurance-running nutrition products don’t contain the ingredient. If you opt for real food, do your research to know how many calories you are ingesting and be sure to know exactly how it makes your bowels move prior to race day. Also, real food can be a challenge to digest when running in certain conditions, like in heat or at significant effort. In other words, for several reasons, use caution when eating real food on runs of two to four hours.

Now it’s time to head to your local running store to look at the shelves of colorful labels and shiny packages! Start small with a few flavors and few brands. If you find something you like, stick with it while experimenting with other products to see if there is something that works even better. You got this!

Chris Mocko - 2017 Behind the Rocks 50 Mile

Chris Mocko grabbing some gels from an aid station at the 2017 Behind the Rocks 50 Mile. Photo: iRunFar/Meghan Hicks

The basics of running nutrition can be daunting, so here are the key takeaways of this article for consuming carbohydrates on runs lasting two to four hours:

  • Plan to take in calories if you are planning to run longer than 90 minutes at a meaningful-to-you effort.
  • Try to ingest 150 to 300 calories an hour for any runs lasting longer than one hour. Avoid consuming more than 300 calories, as your body may not be able to digest what you are eating as fast as you are eating it. Basically, aim to eat what helps you feel energetically strong and digestively at peace.
  • Add protein–via products containing amino acids–if it makes you feel better.
  • Don’t add fat to your diet while actually running unless you’re adapted to it.
  • Pick your poison of gels, chews, solids, powders, or other options. There are a lot of ways to get these calories, so find the one that works best for you.
  • Track your caloric intake–both in terms of what you are eating and the rate at which you are eating it–in your training log so you can easily look back to find what worked and what didn’t work. Also note how what you’re eating makes you feel.

Finally, as we mentioned at the beginning of the article, don’t be talked out of what you know works for you. Every person is different, which is exactly why there are so many products and so much information about running nutrition out there. With all the variety, you will find something that works–even if it is a bar made out of cricket flour. Once you find that secret sauce, don’t let someone else tell you that you are wrong for using it. Their body may work slightly differently from yours.

It’s certainly good to experiment with different fuels and ways of fueling if you are having trouble with energy and digestion while running, but try not to do so on critical runs and at races. Experiment on a day when an extra loo stop or energy lull isn’t going to ruin your outing. In races and during critical long runs, stick to what you know works for you and enjoy the benefits of staying fueled while running!

Call for Comments (from Meghan)

  • For those with some experience in fueling while running, can you share an example of what you ate and how you ate it during a long run or race when you got your nutrition ‘right?’
  • And, how about a story from when you running nutrition was ‘wrong?’ Specifically what did you eat, how much did you eat, and what problems resulted?
  • If you are just getting started with fueling on trail runs, what specific questions and needs do you have? Leave a comment to start a discussion.
May Queen Aid Station at the Leadville Trail 100

The May Queen Aid Station at the Leadville Trail 100 Mile in Colorado offers all kinds of food to passing runners. Photo: iRunFar/Meghan Hicks

Rhielle Widders

is passionate about introducing her favorite sport to newcomers. She created and directed the Park City Trail Series, a four-race series designed to get people running on dirt, from 2010 to 2014. When she isn’t in Park City, Utah, where she lives, you will find her traveling to try out new dirt. Follow her on Instagram.

There are 34 comments

  1. Zak Steigmeyer

    This is a good intro. Seems like it would be good to add that intensity of exercise has a big effect on the ratio of glycogen to fat that your body uses.
    Also, the amount of calories that a person can digest while exercising is a trainable thing- if you try 200 calories per hour on a run and it makes you puke, that doesn’t mean you should never try it again. For runners that never eat on the run or close beforehand, I think it’s better to view the fueling as part of the training rather than something to try out once or twice before the first long race.

  2. Cary

    For years I had debilitating nausea trying to take in enough carbohydrates to not bonk on long runs. My only solution was to become fat adapted so that I did not need near as much. I also got some good advice from a very successful runner I knew. She said, if you are having stomach issues, shoot for the least amount of fuel you need. This advice helped immensely, especially as I slowly became better at burning fat. Yes, some people can train their stomachs to process more carbs, but you can also train your body to need less.

      1. Cary Stephens

        James, when I made the switch I scoured the internet on fat adaption and metabolic efficiency training. There is a bunch of good information out there. Look for studies/books by Phinney and Volek. The F.A.S.T.E.R. study is the one that pops up most often. On the training side, while the Maffetone method did not fit my heart rate zones well, (oddly, it had me running too fast), his general premise of running low intensity to build your aerobic engine did work.

        I must say that basing your decisions on studies or averages is only a place to start. Ultimately in every study there are a ton of outliers on the graph. In other words, nutrition can be very individual. Fat adaption through high fat diets may not be appropriate for some (maybe most) people who have no issue processing sufficient carbs to excel. But for me, I had to try something different to stop my puking. It worked. Good luck.

      2. J Mex

        The book, What the Fat (for athletes) (Professor Schofield) is good. As is “The Art and Science of Low Carbohydrate Performance” by Volek and Phinney

  3. Nelson

    I find that one or two small slices of bread with jam (jelly) carry me through my typical 10-13 mile run with 1200-2000 feet of gain. It gets digested quickly enough that I don’t experience any issues. I’m 171 pounds, so I imagine lighter runners can get away with less. I used to do these same runs on no food when I was 160 pounds a year ago. I probably was also slower then.

    For long runs, chocolate sandwich cookies, similar to Oreos, have worked really well. A little over 100 kcal per cookie. Drinking Nestea (in addition to the cookies) helps taking in more carbs and it keeps my stomach happy.

    In both cases, it allows me to charge the uphills at the end of a run, which wasn’t always the case when I didn’t eat during or right before going on a run.

  4. Andy M

    A couple other personal observations from one who has, like many, struggled with nausea and puking during ultras. Protein and fat both help to slow carb absorption, probably why PB is often a go-to at aid stations (I’ve found nutty Kind bars low in sugar work well) and are easy to stick in your pack or even pocket. Also, for me, my GI tract reaches a limit on the amount of simple carbs it can take after 5-6 hrs. Hence savory foods (e.g., noodle soup, savory sandwiches, even burritos!), though difficult to carry with, are staples at late night aid stations during 100s and can go down much easier than gels or fruit. If you doubt the aid station fare put some Panini in your drop bags!! Lastly, overheating and dehydration always makes the GI troubles worse, so drink plenty of water and stay cool to help keep stomach acids and nausea at bay.

  5. Rob Sargeant

    4-5 hours into an ultra I’ve found that crispy bacon is good. I’ve also tried adding a bit of sweet potato. It helps to settle my stomach after taking in so many gels.

  6. Guy Love

    Gels are gels, but I don’t really know why people buy blocks rather than going to the grocery store for Sour Patch Kids or gummy bears, ~700 calories for $1.50. It’s all sugar more or less

    1. Mike

      No its not. Gels do not contain sugar. They contain other forms of carbohydrates much more easier and faster to digest and metabolized .

  7. Ali D.

    Check out Muir Energy – real food nutrition packaged like a gel. Best thing out there for endurance athletes. No additives or preservatives. Hand-made in small batches. Available online and at about 40 retailers nationwide.

    1. Tara

      I was super excited about Muir products but had digestive problems from them, so even though their real food, that doesn’t mean they’re easily digestible. Also… they have a much shorter shelf life than other gels. Just FYI – I had a few go bad! The packages get all swollen!

  8. Guil

    Training for my first 50K this past February, I was fueling my body with mostly gels and some waffle bars and I was doing fine. But when race day I started on my normal routine of gels and water, 3 hours into my run I could no longer handle gels anymore. I would fuel on mini pbj’s and bean/cheese burritos at the aid stations and take them with me. That is what got me going and thru my frist 50K, I was quite surprised because during my long training runs gels were working just fine for me.

  9. Jason Culverhouse

    In training for my first 100 miler I actually looped into our local donut shop. (I’m a Texan and lived in a small town so the options were super limited on early morning runs). I began practicing by getting a couple of colaches and just eating the bread. After a while I began eating the sausage with the bread. I knew I had prepared my stomach well the day I graduated to the jalapeño colaches. I never got nauseous at the race and was able to mow anything down on the table. Hey, prepare for the worst and have fun, right!

  10. Dennis P. Lima

    I just ran my first 55K a couple of weeks ago here in Colorado. I just drank my usual coconut water and had a few gels, along with some watermelon at the aid stations. All went fairly well. I’m sure I’ll need more when I run a 50 miler or more, we’ll see.

  11. Penny Williams

    Running my first ultra this February, trying out fueling on my long runs, boiled potatoes, fruitcake was recently recommended, love the spring gels that I use in my water bottles that I add water to, but I have such GI issues, running diarrhea, that I worry about eating at the aid stations , so trying out what is served on my long runs, anyone have recommendations for this issue

  12. Craig Lunaas

    Any there any Keto runners out there who are incorporating carbs back into your ultras? My first 100 was on pure carbs, but I enjoy the Keto lifestyle (and my labs), so on my next 100 I’ll mostly use my fat based foods. I know that I’ll probably need carbs also, so any experiences that you all have had would help. I’m going to read the books referenced above, and experiment on a few spring ultras, but suggestions always help. Thanks!

    1. Cary

      Craig, I was keto when I worked on getting fat adapted in 2014. In 2015, I slowly (over my last 2 months of training) incorporated gels and other carbs back into my long run nutrition plan leading up to my first 100. I did not have to take in very much however. My total calorie consumption on race day was around 150 Kcal per hour and that was a mix of gels (maybe 10 in 27 hours), sports drink (maybe 6 bottles), nut butter, soup and a few hand fulls of pretzels and potato chips. I just nursed a sports drink and took a gel before the big climbs. FYI-Long before the race, I wondered whether taking sugar might impact my fat burning efficiency, but I tested that at a lab for fun after doing a Vo2Max test. Just after finishing my test I took a gel, waited 15 minutes and jumped back on the treadmill. The gel did not change my metabolism. My high fat metabolism at key intensities was identical to my prior test results.

  13. Mark

    I like those pouches of pureed baby food, any brand that you prefer. They come in lots of flavors, they’re tasty, and they’re healthy.

  14. Stephen Horner

    I like english muffins with almond butter every 45 minutes. I don’t like gels or chews as they seem to bomb out my stomach. In the past I would take a water bottle full of table sugar, instant oats and a diced up pear. It was a massive quantity of carbs. As I am not a racer, rather, someone that just loves long mountain runs, this worked great at a point in the run where I would take a break and walk a bit to allow those carbs to get through my stomach.

  15. MoGreen

    I know someone mentioned them earlier and want to give another recommendation for Spring Hill Energy . They have a range of different gels with different calorie counts.
    My local run shop here in Seattle , where many ultra runners shop , cannot keep the Canaberry in stock , and is a personal favorite as well

  16. Terry Cornall

    I did my longest run, to date, of 60K planning to using only gels. By 40K I was so sick of the taste! Fortunately, aid stations had oranges and watermelon, and they were great. Not a lot of kilojoules, but the change in flavour was just what I needed. So, I recommend that mixing flavours and textures would also be a good idea (some runners I know cannot stand gels because of the ‘slime factor’) .

  17. August

    I was training for my first 50k and had tried out gels on my long runs, but I never found them very palatable and was getting nausea on the course of a run. Lately I just use bars which contain nuts and some sugar these work well for me, especially the peanut variety. I will have some different options with me to vary what I take, to not become sick of one type of food for so long. My mountain 50k with 3900m of elevation in the Alps will take around 10 hours and because of Covid we have to take all solids ourselves.

  18. Mark Phillips

    I am hitting 4.5-5.5 hours at the longest on my long-runs. I consume a moderate amount of water (maybe 2L? Or 3) unless it’s super hot or exposed. I usually pack some nuts and a couple PBJ sandwiches. And I bring salt tabs. I’ve had no GI issues and I end the runs feeling ok…not like I hit a wall, but also like I’ve run 4.5 hours. I am not fat adapted. I have a shorter race (trail marathon, target 4.5-5 hours) coming up and I want to perform well. I’m worried that my diet isn’t race-y enough. I seem to read conflicting stuff about fiber, protein, and fat. Seems like PBJ is high in all three. My race is in six weeks (Moab). Should I be working on a carbier nutrition plan?

  19. Tom Sweeney

    I’ve got my first 54k run coming up. For the 20k runs I have been having bars and tail wind but feel I may need more.

    This has helped a lot, thansl

    1. Meghan Hicks

      Hi Tom,

      Thanks for the comment and good luck in your first 54k! So great that you’ve been training with bars and Tailwind, both are awesome fuel (and hydration in the case of Tailwind!) sources. Practice really does make perfect when it comes to training your stomach to intake calories on the move, so make sure to test your new calories before race day. I hope you’ll stop back by here after your race and let us know how it and your fueling went. Best to you!

  20. Mark Stone

    Thanks Meghan, this is great advice. Like many runners, I’ve tuned my nutrition through a series of disasters!! To emphasise the ‘we’re all different’ comment … I once ran with a guy who carried a pound of cheddar cheese to get him through 100k … that’s it, water and cheese! He overtook me and I never saw him again :)

  21. Rima

    Great article, you covered the basics well.
    I like dried fruits and dates as fuel. Crackers sometimes for something salty. Of course cannot go wrong with Gatorade.

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