David Roche continues to convince us why high-carb fueling is revolutionizing performance. In this latest article, he walks us through the latest research supporting the benefits of high-carb on running economy.
Matt Intro: David and his wife Megan are doing incredible things in ultrarunning—pushing the limits of what’s possible—but that’s not why I trust them. I trust David because he has an uncommon ability to take complex exercise science and turn it into guidance that actually helps athletes train, fuel, and perform better.
Which just so happens to be my mission at The Feed. When new research comes out that could change how we think about fueling or performance, David is one of the first people we reach out to. He reads everything, pressure-tests it in the real world, and then explains what actually matters—without the noise or marketing spin. That’s why I’m excited to bring David’s perspective directly to you. It’s practical, evidence-based, and built for athletes who want to do this the right way.
Please, enjoy David's article.
Every year or two, a handful of researchers in a distant lab click “publish”, and everything changes. That happened last month when a team from Liverpool conducted the most rigorous high-carb study protocol we have ever seen.
The biggest finding was that there was a dose-response relationship between carbs and running economy, with 120 grams of carbs per hour resulting in 2.6% less oxygen cost than 60 grams per hour.
2.6% running economy improvements! That means that even in events that are just 2 hours long, and even coming off a carb load with major glycogen reserves, the difference between somewhat high carb (60 g/hr) and very high carb (120 g/hr) is almost as much as wearing supershoes for the first time.
In other words, this study is the biggest thing to come from Liverpool. Ever. Suck it, The Beatles!
The Study
The study had 8 male marathoners (a companion study on female athletes is coming out soon, and the researchers indicate that there are similar findings) with an average PR of 2:22 have 24 hours of high-carb fueling and a big pre-training meal go through 3 fueling conditions:
60 grams of carbs per hour on pure glucose
90 grams of carbs per hour on 2:1 glucose:fructose
120 grams of carbs per hour on 1:1 glucose:fructose.
And the exercise protocol was SPICY. We're talking 15 minutes steady, 90 minutes moderate, into 15 minutes steady. Basically, they're testing 90 minutes of a fast marathon pace, with plenty of quick running on top of that.
Now imagine we're comparing very high-carb to the levels athletes usually take in on hard training days (some studies put that number as low as 20-40 g/hr, or even fasted).
You can see how high-carb is causing the performance revolution — every single day, fueling involves much better economy than otherwise expected. Stack 2.6% on 2.6% on 2.6% and you get the magic that has changed everything as we know it: compound growth.
There were some interesting wrinkles: The study didn't actually measure max performance, so we're left to extrapolate the economy changes to outcomes.
Oxygen cost was 1.12% lower at 90 g/hr than 60 g/hr, though that difference was not significant.
Even at 120 g/hr, the 2nd hour involved 65% CHO dependency, meaning that fat was still being used at very high levels to sustain performance.
The 120 gram group was just able to avoid fat taking up the majority of the energetic equation, which could cause economy reductions at hard efforts.
All groups reported high levels of GI symptoms, with the 120 gram group reporting the most.
The researchers say this finding shows that you need GI training to make it work. Implied is that the researchers also needed a good janitorial service to clean off the wall behind the treadmill.
And here’s something that’s very relevant for your next purchase: The researchers used a carb drink dosed at 125 mL every 15 minutes. When the carb levels are very high, drink mixes play a huge role in balancing the equation.
Let’s be real: 120 g/hr is best for very hard efforts like races.
For example, I try to be at 150 g/hr for my ultra races, but I rarely go above 90 g/hr in typical training (outside of race-specific efforts and GI training days).
On most of those days, I head out the door with a waist belt and a dream. I simplify the process with a high-carb mix in the bottle, plus another baggie in the belt to refill at a water fountain.
My Go-To High-Carb Drinks
The Feed Lab High-Carb Drink Mix. It’s the least expensive price-per-carb option on the market, just $20 for 33 servings. I’d personally shut down the government if The Feed ever stopped producing it.
Tailwind High-Carb. The lemonade mix tastes like Grandma was an exercise physiology researcher.
Everyone reading this needs a high-carb drink mix in their pantry to help balance the carb equation. When it comes to high carb, I’ll tell you what the researchers told the wall behind the treadmill: get with it, or get out of the way.
