Fuel Like the Best
At least once a month, athletes I coach ask me about fasted running or low-carb nutrition products. My advice is that carbs are your friend. I firmly believe that the ability to consume calories and carbs in a race is a superpower and one of the most important things you can do to improve performance.
Research has pointed towards increasingly higher calories and carbs as optimal for race performance. Studies started to show the benefits of 60-90 grams of carbs per hour, much higher than most ultramarathoners were consuming. Now the mad scientists tell us that 120 grams is best! Even with carb dense products, this translates to a whopping 480 calories per hour.
The catch was that many of these studies were based on cyclists, where it is easier to consume calories without digestive issues. But some ultrarunners have started to hit these levels, approaching 120 grams of carbs per hour. And they are setting the ultra world on fire. Here are just a few examples:
Stian Angermund
Stian won the 2022 Trail World Championships in Thailand. The course was 38km (23.6 miles) with 2,400 meters (7,875 feet) of vertical. He won in 3:08 with a commanding 3-minute lead.
Stian posted his entire race nutrition details, and he consumed a staggering 110 grams of carbs and 446 calories per hour.
Kilian Jornet
The greatest of all time was infamous many years ago for minimal fueling during races. He reported drinking only three liters of water and eating two sandwiches at his first UTMB. Even the GOAT is human though. His lack of fueling resulted in a major meltdown in the 2010 Western States (though he still somehow managed 3rd place), and he has recently talked about previous suboptimal fueling leading to GI distress.
More recently, Kilian has become scientific and meticulous with his fueling, and his results just keep getting better. In the 2022 UTMB, his baseline nutrition was 80 grams of carbs per hour, and he would have hit over 100 grams of carbs and 400 calories per hour with the additional fueling sources cited. Kilian won UTMB, breaking 20 hours and setting the course record.
Petter Engdahl
Petter won the 2022 CCC, smashing the course record by 30 minutes and breaking 10 hours for the first time. He published his race nutrition, citing it as a major driver of his historic performance.
Petter consumed 120 grams of carbs per hour and at least 480 calories per hour. That is some world class fueling right there!
While all three examples with first-hand reporting of fueling details came from male athletes, David Roche cites similar fueling levels for top female athletes like Clare Gallagher, and he reports seeing female athletes fueling at high levels more often than male athletes.
It is increasingly clear that the best athletes in the world are consistently consuming 100-120 grams of carbs and 400-500 calories per hour during races. But what about fueling during training?
Many runners are tempted to fuel less in training to promote fat adaptation. While Kilian has upped his game in race fueling, it is true that he does most runs fasted. However, I believe there are four reasons why most runners shouldn’t do this most of the time.
First, fueling before and during runs improves performance. When you are working to build fitness, especially in hard workouts and long runs, fueling well leads to better results.
Second, fueling well improves recovery. Athletes with higher fueling levels have shown reduced bio-markers of exercise induced muscle damage, such as creatine kinase. Even more interesting, athletes with higher fuel intake had lower perceived exertion during workouts. You have likely observed this in your own running as well. If you become depleted during a race or long run, it is typically much harder to recover with fatigue and soreness lasting longer.
Third, better fueling reduces the likelihood of injury. I often say that the single biggest boost to performance is simply avoiding injury, and persistent under-fueling increases the chances of injury. I have observed over the years that athletes who try fasted running or keto-based fueling strategies get injured more often.
Finally, you don’t just wake up one day with the ability to tolerate 480 calories and 120 grams of carbs per hour while running hard! It is not a superpower you are born with and needs to be honed over time, building up your gut tolerance. It is also critical to experiment and find what products work well for you.
For these reasons, I strongly advocate focusing on consuming carbs and calories the majority of the time. The exception can be during a lower-volume training cycle for athletes following a periodized approach. This would be further out from goal races and when training volume is 50-60% of your max and long runs don’t exceed 2.5 hours. While I do not think you necessarily need to go low-carb during these training phases, the downsides are much lower, so I would not caution against it in most cases.
I have consistently worked on my fueling during workouts and races for two years now. When I first started tracking my nutrition, I was surprised to find I was only consuming 30-40 grams of carbs and 200-250 calories per hour during long runs.
Throughout 2021, I worked hard to notch my fueling up to 50-60 grams of carbs and almost 300 calories per hour. I practiced fueling during runs and experimented and find what products worked well for me. By 2022 I was consistently getting 75 grams of carbs and 330 calories per hour. Nutrition was a big factor in my performance at the Terrapin 50k, Hellbender 100, and Bighorn 100. I was able to close hard in each race and felt strong through the end. I also recovered quickly from each race.
Yesterday I did a four-hour run in the mountains to train for the upcoming Hellgate 100km. I managed 92 grams of carbs and 370 calories per hour. I felt great throughout the run and could have consumed more if I brought more nutrition with me. I will continue experimenting and finding how high I can turn the dials. I cannot recommend enough that you do the same, and you will be amazed to see where your fueling superpower takes you.