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Deep dive into how ketogenic diets and carbohydrate intake effect exercise performance, and misconceptions in sports nutrition.

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.

PRACTICAL TAKEAWAYS:

For workouts over ~60 minutes, consume ~10g carbs per hour (e.g., a third of a banana) to maintain blood sugar and prevent fatigue, regardless of overall diet.
Allow at least four weeks for adaptation when trying a ketogenic diet, enabling the body to fully transition to the ketogenic state.
Monitor personal responses to carb intake, as high levels can elevate fasting glucose even in fit individuals; consider lower-carb options if experiencing metabolic issues.
Prioritize metabolic flexibility through varied diets or fasting periods to improve energy stability, but consult resources for proper formulation to support health.

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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Carbohydrates vs Ketosis in Exercise, Fatigue & Sports Science | Andrew Koutnik | 271

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