The High-Carbohydrate Fueling Revolution: What the Science Actually Says
Based on a talk by Dr. Patrick Benjamin Wilson, Old Dominion University — presented at the ACSM Southeast Chapter Conference
Elite endurance athletes today are consuming 100, 120 or 200 grams of carbohydrates per hour during competition. Sports nutrition products have never been more sophisticated, more palatable, or more portable. The message from coaches, sports dietitians, and pro athletes seems clear: more carbs, faster performance. But is the science keeping pace?
I recently attended the ACSM Southeast Chapter conference and listened to this insightful talk by Dr. Patrick Benjamin Wilson of Old Dominion University. He took a hard look at where the research actually stands and what it still can't tell us about high carb fueling.
How We Got Here: A Brief History of Carb Fueling Guidelines- 2009 – ACSM recommended 30–60 g/hr to maintain blood glucose levels during exercise.
- 2011 – Burke pushed that ceiling to 90 g/hr.
- 2014 – Stellingwerff & Cox proposed a range of 40–110 g/hr depending on conditions.
- 2016 – ACSM updated its guidance to 90 g/hr for workouts lasting 2.5 hours or more.
- 2022 – Podlogar & Wallis suggested 90–120 g/hr may be appropriate.
A key breakthrough came in 2008, when Jeukendrup highlighted the importance of multiple carbohydrate transporters — specifically the SGLT1 and GLUT5 pathways — which together allow the gut to absorb more than the 60 g/hr ceiling long thought to be a hard limit. Then in 2013, Smith demonstrated through a dose-response study that the performance sweet spot lands around 80 g/hr.
Meanwhile, product formulation has improved dramatically. Gels, chews, and drinks are now better designed - easier to carry, more palatable, and better tolerated - making high intake targets more feasible in practice than ever before.
Wilson's own 2025 research on professional cyclists confirmed the trend: carbohydrate intake per hour during competition has been rising steadily since the 1980s.
The Real Question: Is 100 g/hr Actually Better Than 60–90 g/hr?Here's where the conversation gets uncomfortable for high-carb enthusiasts.
When Wilson reviewed the controlled studies with the most rigorous methodology — Mitchell (1984), Smith (2013), King (2018), and King (2019) — the performance-optimizing range consistently landed between 60 and 90 g/hr. Not 100. Not 120.
So why are elite athletes pushing well beyond those numbers? And should recreational athletes follow suit?
Four Reasons the Research Might Not ApplyWilson outlined four important limitations in the current evidence base:
1. The exercise isn't hard enough or long enough. Most studies are conducted at less than 80% VO₂max, and very few extend to the durations seen in real competition. Only one study Wilson reviewed ran as long as three hours. In elite sport, carbohydrate oxidation rates are significantly higher than what lab protocols can replicate - meaning the research may simply be measuring fuel needs at a lower gear than athletes actually race in.
2. Guts aren't trained for high intake. Gastrointestinal tolerance is trainable, but almost none of the studies account for this. Only one study in Wilson's review even asked participants about gut discomfort and fullness. Athletes who regularly practice high-carb fueling in training adapt their GI tracts over time - a factor that lab studies on untrained-gut participants simply can't capture.
3. Higher carbs mean faster glycogen use. A 2025 study by Ravikanti found that higher carbohydrate intake accelerates glycogen utilization and suppresses fat oxidation. This has implications for athletes competing in multiple bouts over consecutive days - where the ability to conserve and replenish glycogen matters enormously.
4. What happens across multiple days? The overwhelming majority of carbohydrate fueling research looks at single sessions in isolation. But triathletes, cyclists in stage races, and ultra runners aren't doing single bouts - they're competing day after day. The cumulative effects of sustained high-carb fueling remain largely unstudied.
What 60–90 g/hr Does Reliably DeliverDespite the uncertainty at higher ranges, the evidence for fueling in the 60–90 g/hr window is actually quite strong. Research consistently shows that this level of intake can:
- Prevent exercise-induced muscle damage
- Improve running and cycling economy (lower oxygen cost)
- Reduce perceived exertion (RPE)
- Decrease cardiovascular strain
- Support recovery between sessions
- Lower the risk of Low Energy Availability (LEA)
- Reduce the energy deficit experienced later in the day after hard training
In other words, even if the case for going above 90 g/hr isn't conclusive, the case for getting to 90 g/hr is solid.
A New Tool: Personalized Carb TestingOne genuinely exciting development Wilson highlighted is a specialized, home-based test from ExoAnalytics that uses stable isotope tracing (Carbon-13) to measure exactly how many grams of carbohydrates an individual athlete consumes versus burns per hour during exercise. In theory, this kind of personalized data could allow athletes to dial in their fueling with unprecedented precision.
But right now, it's too good to be true. Important questions remain unanswered: How many tests are needed to get reliable data? What is the day-to-day variability outside a lab setting? Should athletes test different sugar types separately? Are the numbers trainable over time? How do gut tolerance, body size, and work rate factor in?
The technology is promising but very expensive. Its practical utility for most athletes is still being established. For now, it's a hard pass.
The Big Picture TakeawaysWilson's final conclusions were honest:
For intake above 90 g/hr, the scientific evidence is lacking — not because high intake is wrong, but because it's extraordinarily difficult to study elite athletes under real competitive conditions.
Elite athletes routinely push beyond what science can currently validate. The demands of professional sport exceed the parameters researchers can ethically and practically test in lab settings.
Individual factors matter. Body size, trained gut tolerance, and work rate may all justify higher intake thresholds for some athletes but we don't yet have the research to quantify and personalize those thresholds.
The gap between science and practice is real, and it runs in both directions. Some athletes may be under-fueling because they're following outdated guidance. Others may be chasing intake targets that haven't been meaningfully tested for their needs.
The high-carbohydrate fueling revolution is real, but it's running ahead of the evidence. The science robustly supports fueling in the 60–90 g/hr range for most endurance athletes. Whether pushing beyond that ceiling adds meaningful benefit depends on who you are, how hard you're working, how well your gut is trained, and how willing you are to invest in personalized testing.
For most athletes, the smarter question isn't "how do I hit 120 g/hr?" It's "am I consistently hitting 60–90 g/hr, and is my gut trained to handle it?" Get that right first.
This article is based on a presentation by Dr. Patrick Benjamin Wilson (Old Dominion University, Norfolk, VA) at the ACSM Southeast Chapter Conference.