Update: How Ultrarunning Nutrition Has Changed Since ISSN’s Position Stand

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Update: How Ultrarunning Nutrition Has Changed Since ISSN’s Position Stand

Sometimes it’s good to step back from emerging science of training and ultrarunning nutrition to see how the information holds up over time. What was emerging science several years ago should either be substantiated by further research and practice, or have fallen by the wayside. Several years ago, in 2019, the International Society of Sports Nutrition came out with a position paper titled “Nutritional considerations for single-stage ultra-marathon training and racing”. You can view the whole paper, in its entirety, for free here. Let’s see whether some of the paper’s main takeaways still apply in 2026.

Why Position Stands Matter

The research landscape is enormous, too vast for a reasonable person to consume. All too often, coaches and other practitioners who work with athletes disseminate individual articles as they come out. This is a good way to stay on top of emerging research, but “new” doesn’t always mean “better”. And the distribution of new studies is affected by social media algorithms, so headlines and influencers can give bad studies more attention than they deserve.

Position papers from reputable organizations like the ISSN generally do an excellent job of researching all aspects of a particular topic and then presenting a consensus of the literature. They do this by leveraging many people (there are over 25 authors listed in the paper) and many individual papers (nearly 200).

I read a lot of original research studies and it’s taken a lot of education and time to discern good research from shoddy methods or irrelevant findings. Position papers are a good way for people who don’t read research every day to leverage the expertise of those who do. I read them because people much smarter than I am did the work of narrowing down the best studies, analyzing them, and synthesizing the meaningful and actionable findings.

Ultrarunners Get Bad Advice

Some of the consistent sentiments throughout the 2019 ISSN position stand are that ultrarunners are getting their nutrition wrong and getting advice from unreliable sources. Riddled throughout the position paper are cheeky lines such as:

 ‘(Ultrarunners) tend to favour the insights of other athletes over qualified professionals’

And my personal favorite-

‘Despite the importance of sports nutrition for ultra-marathon training and racing, athletes and coaches face a number of obstacles including (sic)… poor education (of Coach/athlete/support staff).’

Back in 2019, this was a sentiment I agreed with. Based on my interactions with athletes, coaches I met in the field, and postings on social media, the landscape was rife with bad takes, disingenuous advice, and downright grift.

In 2026, has anything changed? I believe it has. This is purely anecdotal, but my impression is that athletes are better educated on sports nutrition than they were seven years ago. There are still beginners who need a lot of education (and that applies to athletes and coaches), but the athletes I encounter at races seem to have greater knowledge about sound sports nutrition principles than they used to. I also think that the professionalism of ultramarathon coaching, which has improved over the same period, has helped educate more coaches so they deliver science-backed advice. Are there still grifters and influencers who promote disinformation? Absolutely. But I’ve always believed raising the bar for professional coaches and dietitians makes it easier to spot the charlatans.

Eating Enough Is Your Greatest Challenge

The ISSN authors stated that “The foremost nutritional challenge (emphasis mine) facing the ultramarathon runner is meeting the daily caloric demands necessary to optimize recovery and permit prolonged and repeated training sessions.” Simply put, eating enough calories is your biggest challenge. It’s not so difficult on easy days, but calorie requirements can easily double (or even triple) on a long run day (>3 hours).

This led to the following advice in 2019:

• On training days over three hours, minimize your caloric deficit during the session itself.
• Aim for approximately 20 grams of protein every three waking hours on big days. So, if you’re awake for 15 hours, that’s 5 x 3 hours or 20g x 5, meaning 100 grams of protein.
• Increase your meal portions on long run days — don’t eat like it’s a rest day when you’ve just run for four or five hours.
• If you still fall short on a big day, make it up on your next rest or recovery day

How does that advice hold up in 2026?

For the most part, I still agree with it. The one aspect I might change is the method for determining protein intake, because it’s best to personalize protein intake by bodyweight. There’s also been a trend toward increasing protein intake for endurance athletes throughout the week and year-round. So, these days I generally recommend 1.5 grams of protein per kilogram of bodyweight for ultrarunners on structured training plans. During periods of elevated workload, particularly when the risk for muscle damage is greater (e.g., mountain running), this recommendation may increase to 1.8-2.0 g/kg/day. And always, protein intake should be spread across the whole day, if practical.

Carbohydrates Are King For Performance

In 2019, low carbohydrate and ketogenic nutrition strategies were very popular on social media and even mainstream media. Nevertheless, ISSN authors concluded that ultramarathoners should consume a diet consisting of 60% carbohydrate, 15% protein and 25% fat. I agreed with that and allowed the caveat that when the training intensity is very high, the percentage of carbohydrate can go up 5-10% from there. Similarly, when the training intensity is lower the percentage of carbohydrate can go down 5-10%.

Specifically relating to a ketogenic diet, the authors conceded there was a ‘degree of benefit’ from fat adaptation, but went on to state, “Ketogenic diets have been associated with acute negative symptoms, including fatigue, headaches, poor concentration, lethargy, GI discomfort, nausea and weight loss.”

And in 2026?

There are still devotees who swear by ketogenic nutrition strategies for ultramarathons, but there are not nearly as many of them anymore. Why? First, the growing popularity of Zone 2 training, which focuses on large volumes of low-intensity training, naturally improves fat oxidation without the dietary manipulation. So, athletes got the adaptation without the difficulty of maintaining ketosis. Second, carbohydrate research showed the benefits of a very high-carbohydrate strategy for performance. Now we have elite ultrarunners consuming 120+ grams of carbohydrate per hour during some races and going faster than ever, although new research from Daniel Plews and his team points out that there’s limited evidence for carbohydrate intakes above 90 g/hr (Plews et al. 2026).

Ketogenic diets have their place for specific athletes who cannot, for whatever reason, take advantage of a high carbohydrate fueling strategy or are doing races with limited support or aid stations. But the research shows that a fat-adapted athlete can, at the very best, match the performance potential of a carbohydrate-fueled athlete. Research has not shown ketogenic diets or extreme fat adaptation to provide a competitive advantage.

Low Carbohydrate Availability Training Has Some Utility

Back in 2019, it was very popular to manipulate carbohydrate availability as a training tool. The idea was that training with reduced carbohydrate availability (commonly called “train low”) improves fat oxidation. That’s true, and the ISSN authors acknowledged that, saying “Nutrition strategies that promote or optimize fat oxidation should be prioritized.”

What we learned by 2026 was that it’s better to increase carbohydrate availability for high-intensity and/or long-duration training and to fuel low-intensity efforts properly and adequately with “normal” amounts of carbohydrate. Here’s why: fat oxidation improves naturally with training volume and easy running. Your body gets better at using fat as fuel when you run a lot at easy paces, without any deliberate manipulation of carbohydrate availability.

If you still want to incorporate a low carbohydrate availability strategy, consider:

• Easy morning runs (<1.5 hours) after an overnight fast and before breakfast.
• Always eat before any interval workouts or high-intensity training.
• Never compromise training quality in the name of metabolic adaptation. Lead with high-quality training, let metabolic adaptation follow.

Gut Training Has Gone Mainstream

Gut training was less understood in 2019 when the ISSN position stand was written and now it is standard practice. The amount of food and fluid your gut can process during exercise is trainable. Just like your legs adapt to more mileage, your gut adapts to more fuel — if you practice it consistently.

Here’s practical advice from a recent article by CTS Ultrarunning Coach Cliff Pittman:

1. Practice Race-Day Nutrition in Training
   Don’t save fueling strategies for race day. Learn to overcome nutritional challenges in training. This includes using the foods and sports drinks that will be available on course, if they are different than what you normally use.
2. Increase Carbohydrate Intake Gradually
   Jumping straight to high intake (e.g., 90g/hour) without adaptation is a common mistake. First, go for a long run and carefully record what you actually eat and drink now. You may be surprised to find you’re only consuming 40-60 grams of carbohydrate per hour despite thinking you’re consuming way more. It’s important to know your starting point so you know how to gradually increase your intake.
3. A Good Nutrition Plan Starts with a Good Hydration Plan
   Adequate fluid intake maintains blood volume, supports gastric emptying, and improves efficient nutrient absorption. Fueling and hydration are not separate, they’re interdependent.

Daily Hydration Matters More Than Ever

One of the simplest and best pieces of hydration guidance that was included in the 2019 ISSN position stand is something I still use and recommend to this day. The WUT self assessment for daily hydration status actually came from a 2005 study by Cheuvront and Sawka, which just goes to show that good science stands the test of time. WUT stands for Weight, Urine and Thirst.

Each morning, ask yourself three questions:

1. Is my weight down from yesterday?
2. Is my urine dark?
3. Am I thirsty?

If the answer is yes to two or more questions, you’re likely going into the day somewhat dehydrated. Address it before training. If all three are yes, particularly over a period of days, then look more closely at your hydration habits throughout the day.

The WUT assessment can give you an indication of how successfully you replenish fluids after exercise, because it’s a look at the longer-range consequences. Post exercise rehydration (from both food and fluid sources) should be 150% of the fluid loss, and you should use drinks and food to replenish sodium lost through sweat.

 

And there you have it! All of your daily nutrition needs for ultramarathon training in a neat summary.

References

https://www.gssiweb.org/sports-science-exchange/article/sse-97-hydration-assessment-of-athletes

Plews, D.J., Booth, P.D., Krieger, T. et al. Fuelled or Fooled? Examining the Evidence and Mechanisms Behind Ultra-High Carbohydrate Intake in Endurance Athletes. Sports Med (2026). https://doi.org/10.1007/s40279-026-02462-z