Carbohydrates vs Ketosis in Exercise, Fatigue & Sports Science | Andrew Koutnik | 271
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Show Notes
Wide release date: December 31, 2025. Not medical advice.
TOPICS DISCUSSED:
* Insulin as a powerful metabolic hormone: regulates nutrient storage across tissues, overriding others like glucagon to promote fat and glucose storage during abundance.
* Glucagon & GLP-1 roles in metabolism: Glucagon mobilizes liver glucose during scarcity; GLP-1, amplified in drugs like Ozempic, suppresses hunger but originated as a diabetes treatment.
* Transition to ketosis in fasting or low-carb diets: Low insulin enables fat breakdown into ketones for brain fuel, allowing survival for weeks without food, with adaptation taking about four weeks.
* Hypoglycemia vs. glycogen depletion: Low blood sugar causes fatigue and irritability due to brain energy deficit, while muscle glycogen levels do not directly limit performance.
* Ketogenic diets & exercise performance: Studies show no difference in endurance after adaptation, with some athletes performing better on low-carb due to enhanced fat oxidation.
* High-carb diets in athletes: In one study, about 30% developed prediabetes-like fasting glucose elevations, linked to total carb intake, despite leanness and fitness.
* Misconceptions in sports nutrition: Guidelines recommend 60-90g carbs/hour, but evidence shows 10g suffices to maintain blood sugar and performance, avoiding insulin spikes that impair fat use.
* Individual variability in diet response: Athletes vary in optimal fuel sources; it’s possible to by athletic and lean but also metabolically unhealthy.
ABOUT THE GUEST: Andrew Koutnik, PhD earned a PhD in biomedical sciences with a focus on exercise physiology and metabolic health, informed by his personal diagnosis of type 1 diabetes in childhood.
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SUBSCRIBER CONTENT BELOW: Practical takeaways, reference paper, episode transcript.