Nutrition for Ultra-Runners Part #4: Workout and Ultramarathon Nutrition


This is Part 4 of a 6 part series. 

Part 1 – Trending Diets in Ultra-Running

Part 2 – Pre-Workout and Pre-Race Nutrition for Ultra-Runners 

Part 3- Post-Workout and Recovery Nutrition for Ultra-Runners

Part 5 – The Best Diet for Ultra-Runners

Part 6 – Training the Gut for Ultra-Runners


In-race nutrition is one of the most difficult components of ultra-running to master.  Even seasoned ultra-runners struggle to dial in their nutrition during ultramarathons.  Understandably so, as countless variables influence ultramarathon nutrition.


  • Length or Duration –  The longer an ultramarathon, the more likely an ultra-runner will experience taste fatigue. It becomes important to supplement carbohydrate drinks, gels, and “runner’s food” with more real food options in multi-day events.  Real food will help prevent taste fatigue and introduce a more diverse micronutrient and macronutrient diet that is likely needed during such long events.  Many can get by sucking down gels and carbohydrate drinks during sub-24-hour events. However, when time and duration extend beyond 24, additional fuel sources are likely beneficial.
  • Intensity – The higher the intensity, the more difficult it is to digest. Blood is pulled from the stomach to fuel working muscles during exercise, inhibiting digestion.  The more intense the effort, the more this effect is amplified.
  • Temperature – Heat acts similar to intensity on the digestive system. Most people cannot take in as many calories during the high heat without gastrointestinal issues.  Additionally, high heat requires more liquid and electrolytes.  For this reason, some have had success with obtaining their calories from drinks during this time.  Slightly cutting down on calories/hr during the heat is also effective.
  • Gut Tolerance – How much can your gut actually handle on a normal day and at race intensity? 250 calories/hr?  375 calories/hour?  Also, what foods does your gut tolerate, and what foods generally don’t agree with you?  While you may not be able to control many factors on race day, you can prepare for them.  You can train your gut and experiment with as many variables as possible during long runs to help develop the best strategy come race day.


A couple of questions that often come up are; when is the right time to take in calories during a run?  Does a run need to be a certain length before calories are necessary or beneficial?

Here are a few different ways people think about this question;

  1. I should only take in calories during races. That way, I will train my body to optimally utilize fat as fuel during training. Then when it comes to race time, I can take in carbohydrates to provide an extra fuel source and further improve performance.
  2. I will fuel only during races AND runs that last over X amount of time or are in excess of X amount of miles. Most do this because they feel they don’t need to fuel during runs that aren’t going to totally deplete them of glycogen, a reasonable assumption.
  3. Fuel for every run. Taking in carbohydrates for every run will ensure I always have enough gas in the tank to train optimally.  The better my training, the better my race performance.

Which one of these do you fall under?  Which one is the best?  In my opinion, #2 (slightly modified) is the best approach, and I’ll tell you why.

The Issue With #1

The philosophy behind #1 sounds totally legit – become a fat-burning machine by depriving yourself of carbs during training, and then when it comes race time, add back the carbs and double up!  This way, you can get the best of both worlds!  This is strategy is often referred to as train low, race high, and unfortunately, it’s not really as simple as all that implies.

I talk about this in the first blog of this series, Trending Diets For Ultra-runners.  Check it out if you want a little bit more detail, but the just of it is this.  When you eliminate carbs from training, yes, you will become a better fat burner.  BUT, you will become a WORSE carbohydrate burner.  Additionally, when you don’t take in as many carbs during training, you are unable to “handle” as many carbs from a digestive standpoint.

To compound the previous point, you miss an opportunity to “train” your gut.  You can train the gut to take in more carbs during runs without causing GI issues.  If you don’t take in carbohydrates during training, you are not only missing an opportunity to train the gut, but you are essentially “detraining” it as well.  Finally, there is no solid evidence to suggest that sacrificing your ability to efficiently burn carbs in exchange for improved fat oxidation is beneficial to endurance performance.

The Issue With #3

If fueling during every run is working for you and you don’t want to change it, then, by all means, stick with it.  Additionally, if you find it very difficult to take in enough carbohydrates and/or other nutrients during the day to support your training load, and fueling during your run provides some of those nutrients, keep doing what you’re doing.

There’s really not a lot wrong with #3 when used correctly.  You likely don’t need to fuel during sessions under 1.5 to 2 hours if you are coming into the run “fueled,” that is, you have replenished glycogen from the previous session.  Additionally, by fueling during these shorter sessions, you likely won’t be burning as much fat, which may slightly inhibit your ability to burn fat as efficiently.  So, I guess that’s my main gripe with this strategy.

Ultra-running is an aerobic sport.  There is likely no other sport where efficient fat-burning is as important.

Therefore, it makes sense to put in a little extra effort to become a highly efficient fat-burner.  Again, that doesn’t mean that you need to do so at the EXPENSE of carbohydrates.  Finally, just by BEING an ultra-runner, you’re going to be pretty darn efficient at fat burning; that’s just part of it.  That being said, during shorter runs, I see more benefit from going without fuel than I do with fuel.


I throw in an unfueled glycogen-depleting long run every month or so.  This will simulate how you are inevitably going to feel at some point in the longer ultramarathon distances.  Remember, even if you’re fueling optimally, you can’t take in as many calories as you burn during exercise.  So you’re still likely to be glycogen depleted in the majority of runs exceeding 50-miles.  It’s beneficial to be familiar with what that feels like.

How to do it – If you have a 4-5 hour (or longer) run scheduled, simply run it without fuel.  If your long run is a little shorter, like 2-3 hours, I’d recommend going into it fasted.  An easy way to do this would be to do it in the morning and skip breakfast.  Simple!

How often – I recommend around 1 glycogen-depleting run/month.  I don’t recommend a lot of these because fasted/highly depleting runs do break you down more – elevated cortisol, increased muscle breakdown, blunted immunity, etc.  I throw these in purely to be familiar with the feeling of having an empty gas tank.  Remember, so much of an ultramarathon is psychological.  AND the longer it goes, the more psychological it becomes.  You don’t want to experience being totally depleted for the first time on race day.


Now that we have discussed when to fuel, the next order of business is HOW we fuel.  In this section, we will answer the most common questions regarding fueling for long runs and ultramarathons.

How many calories should I be consuming? 

According to JISSN (The Journal of the International Society of Sports Nutrition), runners in a single stage ultramarathon should aim to consume between 150 and 400 kcal per hour (Tiller et al., 2019).  I know what you’re thinking – that’s a big range!  True, but the ideal amount largely depends on 2 factors;

  1. How far is the race? A 50k ultramarathon isn’t going to require nearly the amount of kcal/hr as a 100-mile ultramarathon.  Yes, the intensity is going to be a bit higher in a 50k, and as a result, you’ll be burning a slightly higher percentage of carbohydrates compared to a 100-mile race.  But a slight increase in carbohydrate utilization doesn’t bridge a 69-mile gap.

Notice I didn’t ask how far is the TRAINING RUN.  There’s a reason.  That’s because you should fuel during your training runs the same as you are going to fuel during your race!  You might not need 350 kcal/hour for a 4-hour training run, but you darn well better take in that amount in some training runs if you’re planning to do it in a race.  This ensures your gut is “trained” and able to best handle the desired amount of calories on race day.

Ok, I hate to even give a range because so much of this depends on #2, but if your ultramarathon is 50 miles or less, the lower end of JISSN’s range (150-400 kcal/hr) might be fine for you, if you’re running a 100 miler I’d aim for the high end.  The numbers below might be some good places to start;

>50-mile ultramarathon– 150 – 300 kcal/hr

100k to 100 mile ultramarathons – 200 – 400 kcal/hr

Before I get into #2, let’s talk about REALLY long races.  If that’s not your thing, just skip to #2.  How many calories should you consume on 200-milers, multi-days, and beyond?  Well, JISSN hasn’t come out with any numbers that I know of on this topic, but here’s what we DO know.

  • You can digest food better and faster at lower intensities
  • 200+ mile ultramarathons are going to be at MUCH lower intensities than <100 milers
  • You will likely sleep and take substantially longer breaks during super-long ultramarathons

So with those things in mind, I think it’s common sense that the number of calories ingested can be significantly increased, maybe even to the point of not becoming glycogen depleted.  Completion of an ultramarathon is correlated with a greater energy intake (Stuempfle et al., 2011).  Therefore, it makes sense to take in as much energy as is achievable without discomfort.

  1. How much can your gut handle? If you’ve read my other blogs, I’m probably starting to sound like a broken record with this, but here it goes…TRAIN YOUR GUT!  What’s the most common complaint in an ultramarathon and also one of the most common reasons for a DNF?  That’s right.  GI issues!  Yet, so many ultra-runners fail to take in as many calories in long training runs as they PLAN to take in during a race.

How many calories you plan on consuming should be based on how many you have PROVEN yourself to be able to handle during your long runs.  Period.  I will have another separate blog ALL about training the gut in the future.  But, it’s really quite simple.

So now you know the reason for the big range.  Sure there are other things to consider, but these are the main two.

What Kind of Foods or Drinks are the Best Fuels During Ultramarathons or Long Training Runs?

Your staple food in ultramarathons under 24 hours in duration should be comprised mostly of simple carbohydrates – sports drinks, gels, candy, soda, etc.  These are easily digestible and won’t “back you up” to the extent of real food.  Supplementing with real food to give your tasted buds a break from all the simple sugars is fine. Just make sure you test it out in long training runs.

Various studies suggest that sports drinks containing “multiple transportable carbohydrate solutions” are highly effective forms of energy during endurance racing and training (Roberts et al., 2014).  Multiple transport solutions meaning that they contain various forms of carbohydrates.  An effective solution would contain carbohydrates such as glucose (or dextrose), fructose, and ideally the addition of a more complex sugar such as maltodextrin or even better, Cluster Dextrin.

To elimate the guess work, check out Proxima C Endurance Fuel.  It was built specifically for ultra-running and utilizes a no-expense-spared blend of carbohydrates and the electrolytes.  To learn why Proxima C is the best fuel for ultra-runners, check out this blog.

Utilizing various forms of carbohydrates (sugars) increases absorption and gastric emptying time increases the amount of energy you can utilize from carbohydrates and helps to prevent gastrointestinal distress (Jeukendrup, 2010).

As mentioned previously, for ultramarathons lasting longer than 24 hours (some 100s, 200s, and beyond), it is necessary and recommended to eat a significant amount of real food.  A common strategy seen in 200s is to eat simple sugars while on course and eat real food at the aid stations.

How Many Calories from Carbs, Protein, and Fat Should I be Consuming During an Ultramarathon or Long Training Run?   

Ah, the macros.  As most of you already know, the majority of the calories consumed during endurance activity should come from carbohydrates.  Protein is important to prevent muscle loss and unnecessary damage but should be consumed in moderation.  Additionally, supplements such as BCAAs and HMB can prevent muscle catabolism during exercise.

Some choose to nix the protein altogether and replace it with (easier to digest) supplemental amino acids (like BCAAs).  This is all good for shorter races, but for extended duration ultramarathons, some complete protein is warranted as well.  Although carbohydrates are king when it comes to fueling for an ultramarathon, as distances increase (especially to the multi-day range), fat oxidation increases dramatically due to the lower relative intensity of the event.  Additionally, ultra-runners typically start to burn out on high carbohydrate foods/beverages and gravitate towards fat and salt.

OK, so how many?!  Well, it’s not set in stone and is highly dependent upon the race and the intensity an athlete is running.  Factors such as heat and extreme altitude (both increase carbohydrate utilization) need to be taken into consideration as well (Jeukendrup, 2003).  Sorry, I’m going to say it AGAIN – you need to figure out what works best for you DURING training.  Don’t wait until race day.

During a single-stage ultramarathon race, JISSN recommends 30-50 g/kg/hr from carbohydrates and 5-10 g/kg/hr of protein with no real guidelines as far as fat is concerned.  I think a good starting point is to roll with the recommendation from earlier and play with the macros in training to see what best suits you, dependent upon your race distance.

<50-mile ultramarathon– (150 – 300 kcal/hr) – The vast majority can come from carbs as GI distress, palate fatigue, and muscle catabolism are lesser issues in shorter ultramarathons.

100k to 100-mile ultramarathons (200 – 400 kcal/hr) – This might look like 220 kcal (55 g) from CHO and 40 kcal (10 g) from protein.  You might also choose to add in some fat either from the get-go or in later stages when and if palate fatigue and GI distress become issues.

Multi-Day Races – A good strategy might be to utilize a multiple transportable carbohydrate solution or another easily digestible form of carbohydrate while running and take in real food at all the aid stations.  Aim for the high end of the calorie range (400 kcal/hr) or more.

Taking in real food during super-long ultramarathons will ensure you get some protein and fat in addition to important micronutrients for the sustained effort.  Additionally, real foods will prevent palate fatigue and can lift a runner’s spirits.  Supplementing BCAAs and HMB to prevent excessive muscle breakdown is a good strategy as well.   Remember, damage control is increasingly important when you start climbing into the super long races (200+ miles).

What if I Start to Feel Sick During an Ultramarathon?

Suppose you start to develop the common signs of gastrointestinal distress such as nausea, bloating, and/or diarrhea, then it’s likely time to back off a little on calories (and possibly slow the pace) until it passes.  If you’ve been aiming for 300 calories/hour, try cutting back to 200 calories and see if that helps.  If the issues persist, you may have to cut back even further.

If you are not on the verge of puking, forcing yourself to take in at least SOME calories is likely warranted, even if it isn’t exactly enjoyable.

Remember, if you are cutting back on calories to prevent further GI distress in the heat, you STILL need to take in sufficient water and electrolytes!  Many ultra-runners use their drink as their source of fuel AND hydration.  Sacrificing hydration during times of GI distress is not only dangerous but will almost certainly cause additional gastrointestinal stress.

If you’ve been eating real foods switching to simpler forms of energy like carbohydrate drinks can often provide some relief.  Some find it beneficial to replace some carbohydrates with fat. Just remember that fat isn’t going to provide the same efficient energy that carbs do.

Ginger is a very beneficial herb for nausea.  I always keep some on hand, whether in the form of a chewable or a capsule.  There is also evidence to suggest that vitamin B6 can help with nausea associated with pregnancy. Yet, it’s unclear whether this is true in other scenarios, such as during endurance exercise.

Finally, non-steroidal anti-inflammatory drugs can cause GI issues when taken during exercise, especially when used in the heat (Guy & Vincent, 2018).  Avoiding NSAIDs during endurance activity is important, not only for preventing GI issues but for VARIOUS health-related reasons.  Read more on why you should NEVER take NSAIDs during an ultramarathon here.


What Modifications to In-Race Nutrition Should Ultra-Runners Make When Running in the Heat? 

As I mentioned at the beginning of this blog, a high heat index negatively impacts digestion.  The best thing you can do is to acclimate to the heat as much as possible before the race.  Additionally, (if possible) practice your in-race nutrition during long runs in high heat to see how it affects you.  Oftentimes, runners need to decrease their intake by 50-100 kcal/hour during the heat to avoid stomach issues.


Nutritional considerations for an ultramarathon running and training wouldn’t be complete without a discussion on fluid intake.  In this section, I’ll answer some of the most common questions ultra-runners might have in regards to fluid intake during ultramarathon training and racing.

How much fluid should I be drinking?  During a single-stage ultramarathon, The Journal of the International Society of Sports Nutrition recommends 450 – 750 ml/hour (Tiller et al., 2019).  In ounces, that equates to about 15 to 25 oz/hour.  Perhaps a more applicable way to break it down would be 150 – 250 ml (5 – 8 oz) every 20 minutes.  Of course, additional intake may be required for you during very hot days.

To really pinpoint your personal hydration needs, start weighing yourself (naked) before and after runs.  Record the heat index, your weight before your run, and your weight after the run.  This will tell you exactly how much water weight you lost and will give you an idea of what you need to replace during an ultramarathon or a training run.

Don’t forget, when you are sweating, you are losing electrolytes, not JUST water.  You must be replacing electrolytes (namely sodium) as well to prevent hyponatremia (low plasma sodium).  A good way to do this is with a pre-mixed electrolyte drink.  Often common sports drinks do not contain enough sodium to compensate for the loss during hot and humid conditions.  JISSN recommends a concentration of 500-700 mg of sodium per liter to adequately replenish electrolytes during an ultramarathon (Tiller et al., 2019).

For a super-simple way to take in your carbs and electrolytes in scientifically relevant amounts check out Proxima C Endurance Fuel.  Proxima C was formulated with ultra-runners in mind and is an ultra-premium supplement that cuts no corners.  When it comes to fueling ultras and other entended duration endurance events, Proxima C is as good as it gets.


Supplementation of BCAAs has proven to be an effective strategy at combating central fatigue in ultramarathons and long training runs.  Central fatigue is essentially mental or psychological fatigue.  Central fatigue is a big factor in ultra-running and other extended duration sports (that is often overlooked).  The longer the ultra-marathon or training run, the more central fatigue becomes a factor.

Supplementation of BCAAs has various benefits in addition to preventing central fatigue, and they are an easy, safe, and effective addition to any ultra-runners supplement regimen.  To learn more about BCAAs, such as how much to take them, how often, and the various ways in which BCAAs can improve your ultramarathon performance, check out my blog BCAAs for Ultra-Endurance Athletes.


As you can see, nutrition plays a massive role in optimal performance during an ultramarathon.

It is worth your time to learn as much as you can in order to create the best nutrition strategy possible come race day.  Remember, no two runners are alike.  Some runners can suck down gels for 100 miles straight and never have a stomach issue.  Others get nauseous at the thought of gels.

Develop your nutrition strategy based on what has worked for you in training.  Nothing new on race day!



Disclaimer – Use common sense, and always listen to your doctor over a blog post. They know more about your personal health situation than anybody behind a keyboard. As someone who has a Graduate degree in Clinical Nutrition, I realize the variance that certain medical conditions create when it comes to optimal nutrition and supplementation. If you have underlying medical conditions, always check with your doctor before starting a new supplementation routine.



Guy, J. H., & Vincent, G. E. (2018). Nutrition and Supplementation Considerations to Limit Endotoxemia When Exercising in the Heat. Sports, 6(1), 12.

Jeukendrup, A. E. (2003). Modulation of carbohydrate and fat utilization by diet, exercise and environment. Biochemical Society Transactions, 31(Pt 6), 1270–1273.

Jeukendrup, A. E. (2010). Carbohydrate and exercise performance: The role of multiple transportable carbohydrates. Current Opinion in Clinical Nutrition & Metabolic Care, 13(4), 452–457.

Roberts, J. D., Tarpey, M. D., Kass, L. S., Tarpey, R. J., & Roberts, M. G. (2014). Assessing a commercially available sports drink on exogenous carbohydrate oxidation, fluid delivery and sustained exercise performance. Journal of the International Society of Sports Nutrition, 11(1), 8.

Stuempfle, K. J., Hoffman, M. D., Weschler, L. B., Rogers, I. R., & Hew-Butler, T. (2011). Race diet of finishers and non-finishers in a 100 mile (161 km) mountain footrace. Journal of the American College of Nutrition, 30(6), 529–535.

Tiller, N. B., Roberts, J. D., Beasley, L., Chapman, S., Pinto, J. M., Smith, L., Wiffin, M., Russell, M., Sparks, S. A., Duckworth, L., O’Hara, J., Sutton, L., Antonio, J., Willoughby, D. S., Tarpey, M. D., Smith-Ryan, A. E., Ormsbee, M. J., Astorino, T. A., Kreider, R. B., … Bannock, L. (2019). International Society of Sports Nutrition Position Stand: Nutritional considerations for single-stage ultra-marathon training and racing. Journal of the International Society of Sports Nutrition, 16(1), 50.

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