Fuelling Ultra Endurance Events

sarah cuff Endurance Sport, Performance, Running Performance 2 Comments

Seven years ago I found my way from marathons into ultras. A couple years later I wrote a post on How to Fuel an Ultra. Now 5 years later with extensive additional personal and client hands on experience, I have more to add. Plus I find it rather data and numbers driven – a good place to start, but often real life is far more nuanced than that. How to listen to your body wasn’t addressed as much as I feel now it needs to be, particularly as a holistic nutritionist who strongly believes in the wisdom of our bodies and their ability to communicate clearly what they need.

Personally, I’ve now run 18 x 50Ks and 50-Milers, 4 x 100-Milers (plus a 139-Miler, which was actually me DNF-ing a 200 on a looped course) and 1 very mountainous 200-Miler. And I’m thrilled to finally be preparing for my next 100-Miler (124 miles to be exact).

While Tahoe 200 was the last big race I personally ran, I’ve since coached dozens of athletes and runners to 70.3 Ironman, 50K, 50-Mile and 100-Mile finish lines, including one of my runners who’s run 100 miles 3 times on the same route: her first go resulting in 27 hours, 57 minutes; second time a real battle with the heat but she persevered and finished; and very excitedly her most recent attempt landing her a sub 24 hour 100-miler (23:39)! Of course she is now training for her first 200-Miler (as one does, yes?!) and I’m excited to coach her through to its finish line.

Thus, here I will outline 3 key areas you may wish to address as you gather your nutrition together for your next ultra endurance event – be it running a 50K all the way up to a 200-miler, or swim / bike / run an Ironman 70.3 or full Ironman, or anything else you’ll be out there for 5-6 hours or more. And I’ll include plenty of ideas for actual fuel sources you might reach for in order to nourish yourself well.


While fuelling endurance events often can seem daunting and difficult, it can also be a lot of fun (yes, fun!!) to navigate the challenge of putting food and drink into a gastrointestinal system that isn’t fully “open for business”. Because our body is shunting blood to our working muscles, there’s less available for the GI tract. How much less depends on many factors including how hard we are running. If we can build a really strong lipolytic aerobic base via low end aerobic training (aka zone 2) and run endurance events primarily in an aerobic state, we will have a more functional gut – ie more blood flow to the area – not to mention burn less carbohydrates (the lipolytic aerobic system utilizes primarily fatty acids for fuel).

That said, other factors that can also make fuelling more difficult include heat or other weather conditions. Dehydration or over hydration can also complicate matters. And of course fat and protein is harder for the body to break down than carbohydrates (starches and sugars). Lastly, the longer one is out there, the harder things can become as fatigue builds. And in multi-day events (such as a 200-Miler!) we must consider the need for fat and protein as well as adequate carbohydrate, not to mention enough (but not too much) fluid and sodium.

When training for the likes of a marathon, often the best fuelling is simply 30 to 60 (possibly up to 90) grams per hour of pure carbohydrate in the form of sugars (aka glucose, fructose and sucrose – found in many natural gels, chews, and fruit such bananas or dates), or possibly the highly processed glucose polymers derived from starch (such as maltodextrin – which is main ingredient in many mass produced gels and chews). For sake of simplicity, this means approximately 1 gel every 30-45 minutes. You might even keep this simplistic strategy for ultras of up to 12 hours.

In my 2018 Javelina Jundred 100-Miler, I opted to try racing it by using primarily Huma gels and Skratch exercise hydration. It was very hot and ultimately my stomach quickly rejected my sweet fuelling choices. Luckily I was also very metabolically efficient at that time, so I was able to take the time needed, not eat much of anything for a while, and recover from my nausea to still finish that race under 24 hours. I ended up eating a good amount of whole foods from aid stations. I had landed on the strategy of just gels and electrolyte energy drink because I’d very successfully used it for my Baker Lake 50K a month earlier, nabbing my fastest 50K ever. Suffice to say, different distances (and different courses in vastly differing weather) require different strategies!

When it comes to fuelling most endurance events – particularly those that will have you out there more than 12 hours – you’re likely going to want more than just pure carbs and as such, it’s easier to focus on aiming for a certain number of calories per hour. You won’t be able to replace 100% of the calories you burn, but aiming for replacing 30-40% of calories burned is more than reasonable. For a 150 lb person running a moderate pace (burning ~750 calories per hour), that would be 225 to 300 calories per hour – more or less depending on your weight and your metabolic efficiency. Less metabolically efficient means more calories needed. More metabolically efficient equals less fuel needed on the go.

Therefore, aim to consume anywhere between 150 to 350 calories per hour. Consume these calories at either 30 minute intervals (ie, 75-150 cals every half hour) or 45 minute or 60 minute intervals. Less calories at once means less chance of GI issues, but eating so often can get old fast.

For race day, once you know approximately how many calories you will be aiming to eat each hour, multiply that number by how many hours you expect you’ll be out there racing. This will give you a total number of calories you’ll need to pack. I will often do up a spreadsheet for clients listing fuelling sources I know work for them that add up to meet target calories. They might play with it and make changes, but at least it gives them a starting point.

For example, one of my clients was attempting her first 100K race and we guessed she’d be out there for 15-16 hours. Her target rate of replenishment at that time was approximately 260 calories per hour (260 x 15 and 260 x 16 = 3900 to 4200). Thus we aimed to ensure she had at least 3,900 to 4,200 calories ready to consume – that’s how much she’d carry on her and in her drop bags. Aid station food would be bonus. She felt like she ate a ton, eating nearly everything she brought plus some grilled cheese and quesadilla at aid stations. And she felt the best part of the whole race was that she never hit the wall (thanks both to fuelling well as well as solid training), finishing in 16.5 hours. Which was amazing because she encountered double the elevation advertised!

It’s important to note that if you will be out there longer than 12-18 hours (such as some in 100K’s, most in 100-Milers and everyone in 200-Milers), you’ll also need to begin replacing meals missed. In other words you’re not only to replace a percentage of calories burned while moving forward, you also need to consider your basic daily metabolic requirements. Often the best way to do this is by aiming to have 2-3 meals over the course of each day, consuming 400-600 calories in one go, either at aid stations or provided by crew or packed along with you (such as freeze dried meals often utilized during fast packing).

Once you know approximately how many calories you need per hour and how often you’ll plan to reach for them, as well as possibly how many meals you’ll need to replace, now you can go about compiling foods that sound most appealing to you. You’ll want to ensure you include both sweet and savoury foods in your mix, roughly rotating between them to prevent food fatigue as well as gut issues. The direction I always give my athletes is:

  • Consume approximately xxx number of calories per hour (between 150 to 350 per hour per their personal needs aka replacing approximately 30-40% of calories burned);
  • Rotate ‘feedings’ roughly between savoury and sweet;
  • Practice practice practice – every long run try out foods you like the sounds of. Keep what works and digests well;
  • However, when I say “long run”, ideally a long training run you use to practice food is 2 to 2.5 hours or more. Save the less than 2 to 2.5 hours long runs for developing metabolic efficiency by fuelling them with only water or water and electrolytes (no carbs or calories). But bring calories for just in case you need them (I don’t advise running through feeling lightheaded or genuinely hungry).
  • Always keep trying new things as eventually you’ll tire of foods you might currently love. The more variety the better – food fatigue (very real concern in long events) will be less likely to happen if you have more choices.
  • Keep a running list of your favourite foods. Aim to have at least 3-4 sweet options and 2-3 savoury options you know you like. (Unless you are out there for 12 hours or less and are running hard, therefore only need carbs such as gels or a specially formulated very carb-rich drink such as Skratch Superfuel.)
  • Don’t be afraid to eat slightly less or more than scheduled, based how you feel.
  • Never hesitate to abandon the most perfectly laid out plan and choose something you crave more in that moment (hopefully you have it with you – always bring more than you think you’ll need/want).
  • Evaluate what went great / not so great at the end of every training run – try to learn more about yourself with each training run when it comes to fuelling.

I’m a huge advocate of using as many whole, real foods as possible – particularly in training (whereas on race day I might use more sugary carby foods). Too many gels and chews (pure sugars or processed starches) could eventually cause health issues including gut health problems, blood sugar problems, dental problems and lowered metabolic efficiency. And sometimes in hot weather, sweet sugary foods (aka most gels and chews) are unappealing.

In one of my first ultra’s – summer 2016, a 24 hour looped course appropriately called Hamster where we could leave a cooler with food sitting at the home base we’d run by every 2.5 miles or so – I’d packed a plethora of gels and foods including salty, savoury millet burgers. Still with a marathoners mindset I thought I was going to reach for more gels – but even early on they didn’t appeal at all. Instead it was the millet burgers that I reached for, one of the only things that I wanted! It was a very hot day and in hindsight it was probable I needed more sodium.

With some exceptions, generally the ‘shorter’ distances require more pure carbohydrates (up to 12-ish hours) while the longer distances (more than 12 hours to multiple days) call for more fats and proteins along with the carbohydrates.

The faster you’re running (think racing, running hard, anaerobic heart rate), the more pure carbohydrates you’ll want to be consuming. The ‘slower’ you are going (out there to complete the distance, heart rate is totally aerobic), the more you can incorporate fats and proteins and whole foods.

Here is a list of ideas to reach for (starting with whole food options):

[*note I am NOT affiliated with any brands I link to – I simply like them and use or have used them]

Carbohydrate rich sweet options:

While I do advocate for using real food, I don’t generally recommend the last three options in training (anything is fair game in a race), both because sport versions are typically easier to digest/absorb and these highly processed sugary options consumed often lead to systemic inflammation (opening the door to injury) and worsening metabolic efficiency among other issues as mentioned above.

Carbohydrate rich savoury options:

  • Boiled baby potatoes (or mashed potatoes) or yams chunks (with sea salt).
  • Pretzels (sticks, twists or peanut butter filled).
  • Plantain chips – also offers fat.
  • Mini crackers (such as Mary’s Gone Cheezee).
  • Bagel with cream cheese (again, probably a white bagel, easiest to digest because lower in fibre than whole wheat versions) – also offers some fat and protein.
  • Burrito or wrap – tortilla wrap (probably white tortilla) with the likes of beans or hummus, rice, guacamole, salsa, cheese, easy to digest veggies such as shredded carrot… – also offers some fat and protein.
  • Potato chips (ideally cooked in avocado oil, such as Hardbite) – also offers fat.
  • Burgers, pizza, rice or potato soups, grilled cheese sandwiches, mac & cheese, quesadillas and other meals aid stations might provide.

Fat/Protein rich sweet options:

  • Nut butter (such as Trail Butter [NOTE – this is by far my current FAVOURITE product on the market!! and many of my clients are loving it too. It’s really tasty, not too sticky sweet, and a pre-packaged easy to carry product I’m not worried will damage my metabolic health]; Grynd Endurance Butter; UltraFat Nut Butter or simply nut butter packets) – also offers some carbohydrate.
  • Keto Brick.
  • Homemade: Fat Bombs.

Fat/Protein rich savoury options:

  • Bacon strips (some ultras have them available at aid stations, or fry them up beforehand and take them with you!).
  • Preserved meats (beef or bison jerky such as Meatchops or EPIC bars).
  • Preserved cheese (such as Energcheez or cheese strings or parmesan crisps).
  • Savoury Nut/Seed Bites (such as Good to Go savoury bites).
  • Veggie burgers (such as Millet Burgersalso offers carbohydrate).
  • Salted veggie or meat broth, with meat and well cooked veggies.
  • Avocado with sea salt.
  • Boiled egg with sea salt, or scrambled eggs (with bacon!).

You’ll notice that many of the above options contain sodium (particularly savoury options), the one electrolyte we lose in large amounts when we sweat. This is unlike the other electrolytes which we neither need nor loose much of during long runs, including magnesium, potassium and calcium (these electrolytes are found in natural whole foods and are easily replaced post-run from whole foods). We do need to ensure we’re getting enough (but not too much) sodium during an ultra, but how much depends more on how much fluid we’re drinking and our sweat rate.

A few extras you might want to have on hand:

  • Ginger chews or candies, to help relieve nausea should it arise.
  • Caffeine chews (such as Matcha KiK) or caffeine tablets (or coffee at aid stations) or natural energy drinks (such as Guru), for an energy boost. Use caffeine later in ultras (as compared to taking pre-run in marathons or shorter distances), or during the night if running multiple day ultras.


How much you will drink over the course of an ultra depends on many factors including:

  • your personal genetics
  • temperature and humidity
  • intensity of your run
  • how long you are out running (or cycling, hiking, swimming, etc)

Generally speaking, the hotter and more humid it is, the more you’ll sweat thus will need to replace more liquid and sodium lost. The harder you run, the more you’ll sweat thus will need more liquid and sodium.

However, if you’re out there a LONG time, say, through the night – you might find yourself hiking more than running and not sweating much (usually is cooler during the night), therefore you might need less liquid and electrolytes during those hours.

Ideally you are drinking “to thirst”. Drink water or an electrolyte/water mix whenever you feel you need it. Of course you need to stay attuned to your body throughout for this to work – but studies have shown that drinking to thirst not only works, it often works better than drinking to a prescribed amount.

VERY generally speaking, you might start with a rough estimate of drinking about 2 cups (500 ml / 16 ounces) of fluid per hour. However, please know this can wildly vary depending on the factors listed above.

You’ll want to consume approximately 300-400 mg sodium for each 2 cups (500 ml / 16 ounces) of water you consume. However, that number can also vary widely (personal sodium loss rate) and remember that if you’re consuming foods that have sodium in them, you won’t need to have a sports drink cover that amount.

The good news is that our bodies can do a great job of regulating our sodium and fluid needs if only we can listen to their needs. Our brain has a sodium sensor which gives us cravings for sodium rich foods or drinks when we need more salt.

Some good ways to increase your sodium intake during endurance events including the following:

  • Energy (carb-rich) drinks that contain at least 300 mg sodium per serving (such as Skratch Exercise Hydration or Skratch Superfuel; Näak Ultra Energy [w/ protein]).
  • Electrolyte drinks (such as LMNT [1000mg sodium per packet] or Nuun Sport [300mg sodium per tablet]).
  • Broths (such as Pacific Broth [NOT low sodium versions of course]).
  • Salt tabs or chews (such as Salt Stick Fast Chews).
  • Preserved foods such as bacon and jerky.
  • Some potato chips, pretzels, crackers (check nutritional info – looking for 300mg sodium or more per serving to be considered a ‘good’ source).
  • Use actual sea salt for dipping potatoes, eggs, avocado or watermelon in.

I like to put Skratch Exercise Hydration into my front flask (pineapple is my favourite flavour ever, matcha comes in second!) and keep water in the 1.5 or 2 litre bladder on my back. I’ll drink either my sodium rich Skratch or pure plain water depending on what I’m craving. I can never anticipate what I’ll want more of, and each run or race plays out differently! I’ve always found this strategy to work well for me. However each of my athletes lands on their own strategy that doesn’t necessarily look like this.

Both too little and too much sodium can lead to nausea and gastrointestinal distress. Often by the time we get nauseous or experience GI distress it’s either too late or it’ll take hours to come out of. So we really do want to tune into our bodies needs and ensure we are keeping on top of getting ‘enough but not too much’ sodium right from the start.


When it comes to fuelling an ultra endurance event, there’s really no right or wrong – there’s only what works for YOU and what doesn’t work for YOU. This pertains to not only foods, drinks and sodium – but all the other electrolytes and nutrients – as well pacing, clothing, gear and training plan. Some athletes swear by ingesting certain supplements or individual nutrients during events – and I’ve no doubt they might work for that athlete.

You need to figure out you… You might try what sounds good to you from the suggestions above… Read others stories and again, take what resonates. You’ll find that people have fuelled ultra events with everything from:

  • Absolutely nothing (Mike McKnight in a 100-Miler);
  • Mashed potatoes, plus Honey Stinger waffles and chews (Courtney Dauwalter in ultras);
  • Maple syrup with sodium citrate, as well as Skratch Exercise Hydration (Lionel Sanders in Ironman triathlons and training);
  • GU grape Roctane Energy drink, along with Vespa and Muir gels (Jeff Browning in his 100-Milers);
  • An avocado sushi roll, bacon, a burger, coconut milk and rice milk, honey and butter sandwich on gluten-free bread [gluten-free because he’s celiac] (Gary Robbins in The Barkely Marathons);
  • 15 vanilla Gu gels (random guy I chatted with at Squamish 50-Miler).

Not that this is how any of these runners choose to fuel their training or races these days – simply to say pretty much everything has been done and shown to work at some time by someone.

Once you’re off to a start with the basics (target number of carbs or calories per hour as well as fluid, ensuring that via either food or fluids you have about 300-400 mg sodium per 500 ml fluid consumed), keep practicing. You might divert wildly from your starting point and that’s okay.

Every time you find yourself out there running (or cycling or hiking or doing what it is you do), use as many moments as you can to tune into the body. “Hi body, how are you feeling? What do you need in this moment? What would you like now?”

In the beginning you might not get much feedback. Or the feedback might not make much sense. But take whatever info you get and do more research on it as needed to fill in any knowledge gaps. Ask questions of professionals. Eventually the more you lean in to your body, the more you listen AND the more you learn about what seasoned athletes do as well as what science suggests… The more you will hear and understand what it is YOU need.

When I ran my last big ultra (Tahoe 200), I knew by that point there were many different ways I could fuel, many foods that worked for me and likely all would work well enough. I planned to have a certain number of calories on me at all points (more than I care to admit in the form of Hornby energy bars) and make full use of each aid station. This is exactly what I did. Although in one section I actually ran out of food… But after some panicky moments wouldn’t you know it but a through hiker asked me how I was doing and offered me an energy bar. It was all I needed to keep going to reach my next drop bag. Drink wise, I drank water and Skratch to thirst throughout. I made it across the finish line – the sweetest finish line I’ve ever crossed.

I personally like to have a plan going into an ultra, and then kinda freestyle it based on how I feel. I have clients who follow their plans almost exactly – often to successful results and sometimes not. I also have clients like me who take their plan and ‘freestyle’ with it – often to successful results and sometimes not. Fuelling your ultra endurance event is but one important ingredient to a successful race. Training, belief in yourself and your abilities, and how healthy you are overall are a few other very important determinants.

As a human, I am of course biased, and thus come at fuelling endurance events with the belief that metabolic efficiency, overall gut health and systemic inflammation can make or break your ultra experience. Therefore in order to see my athletes reach their potential I support them in increasing their metabolic efficiency, bettering their gut health and reducing inflammation in the body overall as much as possible. A successful ultra fuelling plan is ideally built on this foundation of a strong, healthy body to help secure best possible performance.

From both personal and professional experience, I believe that ultimately the only way we’ll truly gain the ability to succeed in event after event, year after year – even as we age – is to use the calculations, numbers and science as a starting place – and personalize from there. This goes for both fuelling ultras as well as determining what our day to day diet looks like.

Our bodies are amazing and designed to work for us, allowing us to accomplish great feats. If only we learn to listen to them. Lean in.

To deliciously healthy food and stronger faster running… Cheers,

Sarah Cuff, R.H.N.
Sports Nutritionist / Run Coach / Therapeutic Coach

Comments 2

  1. This is incredibly helpful! My dream is to run the Wasatch 100. I grew up in those mountains… I will run my first 14 mile trail race at red mountain March 2nd. I have a lot of work to do and things to learn. Thank you so much for sharing all this information Sarah!!

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