Ultra coach and podcast host Jason Koop (whose show I’ve been on in the past to chat about hydration) famously described ultrarunning as ‘an eating contest on the go’. That was presumably to stress the vital role that adequate fueling and hydration play in determining success in very long races…

Whilst it would be wrong to pretend that fueling shorter duration activities (less than 6 hours in this context) is entirely straightforward, there are undoubtedly fewer variables to consider in, say, a marathon or Olympic Distance triathlon than there are in a 100-mile run or IRONMAN.

Figuring out how much carbohydrate, fluid and sodium you need to perform at your best is a clear route to success during shorter races. But when the duration stretches beyond the length of an uncut Lord of the Rings film, you often need more than target amounts of glucose and fructose to keep your body, mind and gut happy.

Does LCHF work for ultras?

There’s a lot of interest in Low Carb, High Fat (LCHF) approaches to fueling ultra endurance events. In the past we’ve dissected the LCHF approach in detail and concluded that a high-carb approach is the one backed by the most robust scientific evidence. It’s also certainly the strategy most commonly employed by successful athletes that we interact with.

That being said, there’s a crack in the door worth peeking through here when it comes to using LCHF to fuel extremely long, low intensity events.

Because fat is a much more abundant source of energy in your body than glycogen (and can provide proportionally more of the calories needed to power low intensity work), it’s during very long ultras where LCHF is most likely to show benefits, if it’s going to work anywhere at all.

And there are some compelling success stories such as those surrounding top ultrarunner Zach Bitter achieving amazing feats on a generally low carb diet (even though in the linked article Bitter describes carbs as a ‘rocket fuel’ for faster running).

There’s also the fact that it seems almost certain from the wealth of anecdotal evidence out there that some people just respond better to LCHF regimes than others (both day-to-day as well as for their sporting performance), so ruling the approach out altogether would be wrong. The bottom line is that if you have an inkling it might work for you, it could be worth a try.

All that being said, it still seems most plausible that the majority of successful ultra fueling plans benefit from being largely carbohydrate-based, albeit with a wider range of food and macronutrients included for a number of different reasons that we’ll get into as this article unfolds. This idea is backed by a significant amount of evidence gathered in the field. So, our recommendations lean towards carbs playing a major role in fueling your ultra endurance efforts.

Before we get into the meat (or should that actually be the potatoes?) of this piece, it’s worth stating that what follows is not an attempt to be highly prescriptive when it comes to what to eat and drink during an ultra.

There’s such a mind-bogglingly wide range of variables to be considered when you look at different people, dietary preferences, events, climates, durations, and types of activity, that attempting to do so would either end up being a hiding to nowhere or end up a similar length to the Encyclopaedia Britannica.

Instead, the aim is to highlight some of the key considerations you need to make to inform where to start your testing and ultimately figure out what is going to work for you.

How much should you consume and when?

As with figuring out your intake for shorter races, the most fundamental consideration for fueling an ultra is ensuring you consume sufficient calories to maintain your desired pace for the entire distance without ‘running out of gas’ before the line.

It should be obvious, but eating a lot is going to be necessary if you want to keep moving at a reasonable pace for many hours on end. You certainly have the capacity to burn through your glycogen stores in the first couple of hours and you’ll definitely end the race in a significant calorie deficit overall.

To that end, most successful approaches to ultra fueling tend to emphasise taking in as much fuel as is comfortably tolerable, because it’s far easier to under rather than over fuel.

Taking this one step further, I’d say it’s often worth ‘front loading’ your fuel intake in most ultras, as your body’s ability and willingness to absorb calories tends to be at its highest early on in an event and it diminishes as time goes on. This means planning to have more calories available from the start and being prepared to start eating earlier than your instincts might otherwise suggest.

In the same vein, it’s also very common for your body to be more receptive to taking in calories during daylight hours than at night. Because of this, it makes sense to aim for increased intake during the day and being more patient with yourself in the wee small hours, when your body is used to being asleep in bed and not being asked to digest large quantities of high calorie food and drinks!

Whilst any generic guidelines on how many calories or grams of carbs per hour to aim for can never hope to cater to everyone’s individual needs, it seems clear from studies of faster ultrarunners that taking in something in the region of 60-90g of carbs per hour is a good starting zone in which to root some trial and error. You can then adjust this based on how you get on and how many calories you’re trying to process from fat and protein at the same time.

You might tweak the relative amount of carbs down and the amount of fat up a bit if your event is super long (or if you’re more highly fat adapted) and fine tuning the ‘ideal mix’ will certainly take some trial and error.

Sports Nutrition or Real Food?

Getting most, if not all, of your fuel from pre-packaged sports nutrition is a no-brainer for short to moderate endurance events, where taking in palatable, simple carbohydrates is the key to success. Whatever format you prefer - drinks, gels, chews or bars - they all generally work well if your total carb intake is about right. This means you can use your preferred format, whether that's Carb Only Drink Mix, Flow Gel individual energy gels or energy chews.

Personally, I tend to stretch the use of sports nutrition products as the exclusive (or at least predominant) source of my energy during ‘shorter’ ultra events as well. Whilst there’s an increasing risk of becoming a bit sick of the taste or texture of gels after 6 hours or so, I’ve certainly completed plenty of successful IRONMAN, long bike or running races exclusively on these kinds of products without GI issues or declining performance in the latter stages.

This fits with the narrative that glycogen depletion is a major cause of fatigue in these events and that increased dosing of simple carbohydrates tends to correlate with improved performance.

But, when things get really, really long, taste fatigue, hunger levels and morale all benefit more and more from the inclusion of some carefully selected ‘real foods’ to supplement your energy products.

What to go for in terms of real foods is more of an art than a science, because it’s critical that you really enjoy eating them and food preference is a very personal thing. But, here are some decent general rules to help define if foods will be good or bad choices…

Good real foods for ultras should…

  • Travel well and be durable enough to survive a few hours in a pocket or pack
  • Be easy to wrap/open and consume on the move (ideally with one hand)
  • Be relatively carb dense, even if they also include significant amounts of fat and protein
  • Be thoroughly tried and tested in a climate (and at an intensity) similar to those you expect to experience in the race
  • Have a high calorie/weight ratio (especially if you have to carry them on you)
  • Some will be very salty, so you can develop a taste for whether your body is craving salt at a given point in time

Good real foods for ultras should not…

  • Be too messy, crumbly to handle, or dry in the mouth
  • Be very high in fibre
  • Present a choking hazard if eaten in a hurry on the move
  • Melt or degrade in the heat
  • Freeze easily or go totally solid in the cold

The list is not supposed to be exhaustive but gives you some sensible criteria on which to base your trial and error.

To give some actual examples of real food options I’ve successfully used in the past, during the Devizes to Westminster (DW) canoe race (which took about 20 hours to complete and goes through the night in cold conditions), we ate a lot of cold roasted new potatoes dipped in butter and salt, various types of sandwiches with white bread, soup and fruit alongside the usual raft of normal sports nutrition products.

In hotter conditions, many athletes report positive experiences using potato chips (crisps) for the salt/sodium hit and watery fruit like watermelon or mango, if it can be made accessible.

Pro triathlete Allan Hovda is a big fan of his ‘homemade snickers’ treats - used to great effect in his Norweigan record-breaking 24-hour bike ride - and US Ultrarunner Dean Karnazas has famously called ahead to order pizzas during some long runs and allegedly rolled them up and eaten them whole whilst on the move! The list of possibilities is close to endless.

Avoiding GI distress

Gastrointestinal (GI) distress is a leading cause of ending with a dreaded DNF (Did Not Finish) in an ultra. A 2015 study reported that GI issues were the reason 35.6% of non-finishers dropped out of a 161-km ultra, with nausea being the most common symptom (90.5%).

The reasons underlying GI distress are many and varied, but an amazingly common contributor is simply overwhelming your gut with an excessive amount of calories, or a single macronutrient (often carbs), causing a back-up in the system, bloating and (if it gets bad enough) sickness or diarrhoea as your body tries desperately to clear itself out.

The classic way of overwhelming your gut with carbs is to combine the use of gels/chews/energy bars or real food with lots of sugary isotonic or hypertonic sports drinks.

Whilst isotonic sports drinks like Gatorade or Lucozade can be a useful tool for shorter endurance events (and, if used sparingly, can help contribute to a successful ultra fueling plan), if they’re used excessively in longer, hotter races, it’s a recipe for disaster.

Using water and hypotonic (lower calorie) electrolyte drinks alongside solid foods is a much more flexible and low risk approach for ultras. We refer to the trifecta of carbs, fluids and electrolytes as ‘The 3 Key Levers’ for endurance performance and by largely separating them you retain the flexibility to pull on each one to the required extent at different times during an ultra-distance race. This equals less chance of inappropriate dosing of any 1 of the 3 inputs and a happier GI tract as a direct result.

In recent years the term ‘FODMAPs’ has also started to pique the interest of ultra athletes with persistent GI issues, because understanding its implications offers a possible solution to exercise-related stomach problems.

FODMAP is an acronym for ‘fermentable oligosaccharide, disaccharide, monosaccharide and polyols’ (enough of a mouthful to give most people GI distress just reading it...) and they all basically refer to the short chain, tough to digest carbohydrates that are found in many common foods. Research has shown promise that, for some folks at least, reducing or eliminating FODMAPs from the diet at key times could reduce GI issues.

Because they’re found in many common foods, FODMAP-free diets are not always easy to implement in reality - and doing so is far from a guaranteed ‘cure’ for GI issues. But, if you want to know more about this topic, a good starting point is this summary article.

What about hydration?

We’ve written a great deal about hydration and sodium intake for long - and especially for hot - races, and there are links to relevant articles distributed throughout this next section if you want to get into the detail on any specific aspect of this topic.

Of particular interest to anyone doing an ultra is perhaps this piece on how much dehydration you can tolerate before your performance starts to suffer.

Suffice to say that hydration needs are both highly individual in terms of fluid and sodium requirements, as well as being heavily influenced by environmental factors and pacing.

It’s also important to point out that whilst there’s something of a ‘more is better’ mantra when it comes to energy intake in an ultra, this is definitely not true when it comes to hydration. Too much fluid (especially plain water or weak sports drinks) can lead to hyponatremia - a dangerous condition that has taken the lives of a few unfortunate ultra athletes over the years, as well as ruined the races of countless more.

To give you an idea of the range of fluid intake levels we’ve seen work with athletes in ultra events, these can start as low as 200-300ml (~7-10oz) per hour in colder conditions and/or when intensity and sweat rates are low. They can climb to 1,000ml (~34oz) or more in hot and humid climates and with athletes who exhibit very high sweat rates.

Optimal sodium (they key electrolyte when it comes to staying hydrated) intakes also vary significantly from between ~200mg per hour up to around 1,500mg per hour. As well as being very individual based on (mainly genetic) differences in how salty your sweat is (i.e. your sweat sodium concentration), sodium needs tend to roughly track your overall fluid requirements, so are much higher in the heat and humidity than when it’s cold and dry (as you might expect).

A mismanagement of your fluid and sodium intake can have a knock-on effect on fueling because reduced blood volume (one of the main consequences of dehydration) can reduce the blood flow to your gut and negatively impact the ability of your body to absorb nutrients. The general level of fluids and electrolytes in your stomach and gut can also impact GI issues and absorption rates further, so keeping the hydration plate spinning nicely is a huge deal in an ultra.

To nail your hydration in an ultra, the best approach is to start to understand your likely range of fluid and sodium needs. Taking our Fuel & Hydration Planner, or having a full Sweat Test if you’re able to, can be helpful in that regard.

Take the Fuel & Hydration Planner

On the back of that, putting together a flexible hydration plan that gives you some guardrails to stay within on race day when it comes to your fluid and sodium intakes, whilst also listening to your body and responding to its feedback, is vital.

The concept of ‘drinking to thirst’ has been heavily promoted in recent years as the answer to all hydration questions - and that’s not without some merit. But, we discuss the pitfalls of relying on this approach exclusively here and it’s a subject that’s extremely relevant to ultras in particular.

The closing comment in that blog sums things up nicely:

In reality, most people’s hydration plan should involve some strategic and premeditated consumption of fluids and sodium, balanced with a healthy degree of relying on ‘drinking to thirst’ to ensure that you don’t end up vastly over (or under) doing your intake on a given day.

What to do if things go wrong

It’s worth considering some of the common signs that your fueling plan has gone awry and what you might do about it to try to salvage your performance.

Achieving the ‘perfect’ ultra from a fueling point of view is unlikely, so don’t be surprised if you have to roll with the (gut) punches on the day and make some changes in order to correct your course.

Here are some steps to take if you hit fueling issues during an ultra...

  1. Stay calm. Try to think rationally and avoid getting too down on yourself about it. Ultras are, by definition, long events and in most scenarios time can be gained back later once you’re back on track.
  2. Focus on defining what the issue is (e.g. lack of energy - a bonk, thirst / dehydration, GI distress, cramping etc) as this will point towards the best remedy.
  3. Slow down. Reducing your pace is often helpful on its own. Act on your best instinct of whether you need to take in more of something (e.g. sugar, fluid, sodium) or whether you may have taken in too much and need to hit the brakes for a while to give your body a chance to process what it’s dealing with.
  4. If you think you need ‘more’ of something, don’t overdo your intake in a short space of time, as that will just make things worse. Treat your body with respect and aim to coax it back rather than bullying it into behaving!
  5. If possible and safe to do so, keep moving whilst you rectify the problem. As long as you’re moving, you’re progressing towards the line. Stopping dead for a rest should be a last resort, as getting going again is tough. Sitting down is like putting one foot in the DNF grave, so only do so if entirely necessary!

Hopefully you won’t ever have to follow the advice in that last section and this post will prove helpful as you strive towards an ultra fueling plan that works for you. If you have any questions about fueling or hydration, please do reach out to us at hello@precisionhydration.com or on social media.

Further reading