108. Testing how many grams of carbs we really need per hour with Isabella Bertold

In this episode, I’m joined by Isabella Bertold, a professional cyclist and former world-class sailor, to talk about what happened when she took a test to find out exactly how much carbohydrate her body needed to fuel her cycling - and the results surprised her.

Like many endurance athletes, Isabella assumed she was fuelling well enough. But after taking a metabolic fuel test using XO Analytics, she discovered she’d been significantly underestimating her carbohydrate needs. The test revealed she could absorb between 110–128 grams of carbs per hour, far more than the 75 grams she thought was her limit.

We discuss what that means in practice - how she’s adjusted her fuelling strategy, what she’s learned from trialling different products and ratios, and why individual testing can change everything about how you train, race, and recover.

Isabella also talks about her past experience with under-fuelling, her fascination with health tech, and how she now uses tools like Hexis and skinfold tracking to monitor performance and energy balance without obsession.

We dive into the ongoing misconceptions about fuelling in women’s cycling, why proper carbohydrate intake is crucial for performance, and how a data-driven approach can replace guesswork and fear with confidence and strength on the bike.

--

BECOME A FUELLED CYCLIST

🧰 Get your free Nutrition Assessment: https://www.gemmasampson.com/ceacq

⛽️ Join The Fuelled Team: https://www.gemmasampson.com/join 

CONNECT WITH GEMMA

🌐 Website: https://www.gemmasampson.com

🎥 Youtube: www.youtube.com/@drgemmasampson 

📸 Instagram: https://instagram.com/drgemmasampson

🎤 Podcast: https://www.gemmasampson.com/podcast/108

🚴 Strava: https://www.strava.com/athletes/5723475