What’s the most efficient way to fuel human performance during endurance sports? For decades, adherents of keto- and low-carb high-fat diets have battled online with those who favor carbohydrate-burning approaches. In this episode, we have on the global scientific expert whose fascinating studies solved the debate.
Australian Louise Burke is one of the best-known sports nutritionists on the planet, known for her Supernova race-walking studies that showed that keto- and low carb, high fat diets don’t fuel endurance athletes as well as carbohydrate-burning approaches. She also practices what she researches, holding the women’s Australian marathon record in her age group—the age group, she jokes, of “never you mind.”
In this episode Dr. Burke walks Stu and Marty through her research that found carb-based approaches to fueling yield about 5% more of the muscle cell’s energy currency, ATP, compared to fat-burning approaches, with carb-burning also yielding 7-8% better performance. “Even though fat can do the job,” Dr. Burke says, “it’s not going to be able to produce the same amount of ATP so therefore you’re going to be slightly slower even though you’re working at the same relative oxygen utilization.”
She also:
—discusses her own approach to fuelling endurance events, before and during races
—provides tips on carbohydrate periodization for everyone from elite performers to recreational athletes
—explains how to train the body to become a fat- or carb-burning machine
—describes the swings between carb- and fat-fuelled approaches to endurance training
—answers a listener question about carb-loading
—tells the origin story of the important Supernova race-walking studies
—explains why race-walking is so perfect for nutrition studies
—shows that carbs during a race are good not only for muscle but also for the brain
—describes the high-fat approach to fuelling she used to help the swimmer Eva Buzo become the first woman to swim from Italy to Albania
GUEST BIO
Professor Louise Burke OAM, PhD, APD
Louise is a sports dietitian with 45 years of experience in the education and counselling of elite athletes. She worked at the Australian Institute of Sport for thirty years, first as Head of Sports Nutrition and then as Chief of Nutrition Strategy. She has attended 6 Summer Olympic Games with the Australian Olympic Team (1996-2012 and 2021). Her publications include over 450 peer- reviewed papers and book chapters, and the authorship or editorship of several textbooks on sports nutrition. Louise was a founding member of the Executive of Sports Dietitians Australia and is a Director of the IOC Diploma in Sports Nutrition. She was awarded a Medal of the Order of Australia in 2009 for her contribution to sports nutrition, and a Doctor of Science (Honoris causa) from McMaster University, Canada in 2024. Louise was appointed as Chair in Sports Nutrition in the Mary MacKillop Institute of Health Research at Australian Catholic University in Melbourne in 2014 and took up this position in a full-time capacity in 2020. X: @LouiseMBurke IG: https://www.instagram.com/louiseburke4
Send us ideas for future episodes, comments and listener questions at realexercisescience@gmail.com
Exercise Science is powered by EverMe, the longevity intelligence app. To get a free two-month trial to EverMe exclusively for Exercise Science listeners, go to:
Thanks also to our sponsor Biafit, your all-in-one fitness platform designed to help you become the best version of yourself. Enter the promotional code HARDFACTS at checkout to receive a one-time 10% discount on the purchased subscription. Download BiaFit at your favorite app store, and learn more here:
https://getbiafit.com/
Exercise Science sponsor Precision Nutrition is the #1 most recommended nutrition certification program in the world. And now it specializes in GLP-1 coaching. For a free assessment to learn your GLP-1 type, visit GLPCoaching.com.
EPISODE LINKS
American Journal of Clinical Nutrition May 2026 feature:
Does a low-carbohydrate diet impede endurance sports performance? Yes
Does a low-carbohydrate diet impede endurance sports performance? No
Does a low-carbohydrate diet impede endurance sports performance? Debate Consensus
Carbohydrates for training and competition. J Sports Sci. 2011
Re-examining high-fat diets for sports performance: Did we call the “nail in the coffin” too soon?
Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J Physiol. 2017
Organization of dietary control for nutrition-training intervention involving periodized carbohydrate availability and ketogenic low-carbohydrate high-fat diet. Int J Sport Nutr Exerc Metab. 2018
Ketogenic low-CHO, high-fat diet: the future of elite endurance sport? J Physiol. 2021
Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible. PLoS One. 2020
Swimmer Eva Buzo’s trans-Adriatic swim chronicled here and in Balkan Insight.
SHOW LINKS
Follow or subscribe at your favourite platform @realexercisescience: Substack. YouTube. TikTok. Instagram. Apple Podcasts. Spotify. On X you can find us @realexscience.
Stu is everywhere, too, but mostly on Instagram and X. Follow him on TikTok too!
Marty just started his own Instagram. Give him a follow! He’s also on X!
Exercise Science is produced by Ghost Bureau, the Toronto content agency.
DISCUSSION POINTS
00:00 Cold open
00:54 Human Performance Fuel
03:45 Field Origins
04:55 Glycogen Supercompensation
06:08 One-Size-Fits-All Failure
06:53 Carbohydrate Periodization
09:02 High-Fat Diets
11:56 Carbohydrate Downregulation
13:49 Keto Diet Appearance
17:02 Supernova Program Setup
21:18 Study Methodology
22:08 Race Performance Outcomes
22:34 Oxygen Economy Analysis
26:45 Recreational Application
32:06 Race Fueling Strategies
DISCLAIMER
The Exercise Science podcast is for educational and entertainment purposes only and is not a substitute for professional medical advice. Strength training and fitness carry inherent risks. Always consult with a physician or qualified healthcare provider before starting any new exercise program or making changes to your diet. The hosts, producers, sponsors and guests of this podcast disclaim any liability for any injuries or losses connected with the information discussed in this show.
The science of strength and fitness is continually evolving. While we strive to provide accurate, evidence-based information, we make no representations or warranties regarding the completeness, accuracy, or timeliness of the information discussed.
Martin Gibala is an advisor to and holds equity in Longevity League Ltd., a US-based company whose services in part relate to exercise.
