Why 90 Grams of Carbs Still Beats 120 | Paul Booth, UTMB-Winning Performance Nutritionist

Paul Booth is a performance nutritionist and exercise physiologist who works with elite ultra-endurance athletes and teams, including the Salomon International team, and was the nutritionist behind both the men's and women's UTMB winners in 2025, Tom Evans and Ruth Croft. We cover the science and practice of fuelling: how many carbs you actually need, why the high-carb trend has run ahead of the evidence, and how to get hydration and electrolytes right for triathlon and ultra-endurance racing.

HIGHLIGHTS AND KEY TOPICS:

• Why Paul calls himself a "90-gram carb guy" and where the carb ceiling actually sits
• What the science says about 90 versus 120 grams of carbohydrate per hour
• The physiology of carbohydrate absorption, and how to work out your own intake for an Ironman without lab testing
• Gut training: building tolerance to carbs and fluid in the weeks before a race
• A simple DIY method to work out your sweat rate and fluid needs
• Why hydration, not carbs, is behind most race-day gut problems
• Electrolytes: what the evidence supports and what is mostly marketing
• Fuelling through heat, altitude and ageing, plus listener questions on glycogen-depleted training, honey and more

SHOWNOTES, LINKS, RESOURCES AND RELATED EPISODES:

• Follow Paul and Performance Gains Nutrition on his website and Instagram
• The shownotes for today's episode can be found here.
• The full podcast episode archives (including category filters) can be found here.
• Related episodes:
  • Carbohydrates, science and practice with Tim Podlogar, PhD | EP#354
  • Nutrition and hydration data from Kona and 70.3 Worlds with Andy Blow | EP#365
  • Aerobic training and testing with Scott Johnston | EP#326
  • Richard Laidlow | EP#403

  Studies discussed:

  • Fuelled or Fooled? Examining the Evidence and Mechanisms Behind Ultra-High Carbohydrate Intake in Endurance Athletes - Plews et al. 2026
  • Graded Carbohydrate Ingestion up to 120 g/h Attenuates the Reduction in Critical Power Following 3 h of Moderate-Intensity Exercise in a Dose-Dependent Manner - Norte et al. 2026
  • 13C-labelled glucose-fructose show greater exogenous and whole-body CHO oxidation at 120 vs 60 & 90 g/h in elite male marathoners - Ravikanti et al. 2025
  • Exogenous Glucose Oxidation During Exercise Is Positively Related to Body Size - Ijaz et al. 2024
  • Fructose-maltodextrin ratio governs exogenous and other CHO oxidation and performance - O'Brien et al. 2013
  • Nutritional intake and gastrointestinal problems during competitive endurance events - Pfeiffer et al. 2012
  • Modelling sodium requirements of athletes across exercise scenarios – when to test and target, or season to taste - McCubbin 2022
  • Could It Bee? Honey Ingestion Induces Comparable Metabolic Responses to a Traditional Carbohydrate Sports Product - Fortis et al. 2025

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