What actually happens inside your body when you fast, and how long do you need to fast to activate meaningful cellular changes?
In this episode of the Empowered Nutrition Podcast, Erin Skinner, DCN, RD, IFNCP, FAND, is joined by endocrinologist Dr. William Hsu, Chief Medical Officer of L-Nutra, and registered dietitian Ashley Bizzell, MS, RD, Director of Clinical Nutrition at L-Nutra Health.
Together, they break down the science of fasting and explore how different fasting strategies may affect metabolic health, cellular repair, and healthy aging.
You'll learn the difference between daily time-restricted eating and prolonged fasting, what happens during a five-day Fasting Mimicking Diet, and why simply eating fewer calories isn't the same as creating a fasting response at the cellular level.
Dr. Hsu also explains autophagy, the body's cellular recycling process, using practical analogies to show how cells respond when nutrients become scarce. The conversation explores nutrient-sensing pathways, why protein is intentionally reduced during a Fasting Mimicking Diet, and how periods of fasting may complement periods of nourishment and rebuilding.
In This Episode, You'll Learn:
• The difference between time-restricted eating and prolonged fasting
• What happens during a five-day Fasting Mimicking Diet
• What autophagy is and why it matters for cellular health
• How nutrient-sensing pathways respond during periods of fasting
• Why fasting is about more than simply reducing calories
• Why the Fasting Mimicking Diet is intentionally lower in protein during the five-day protocol
• How fasting may support metabolic health and healthy aging
• Why more fasting isn't necessarily better
• How to balance catabolic periods of fasting with nourishment, recovery, and rebuilding
• Why maintaining lean muscle becomes increasingly important with age
• How food quality between fasting periods affects overall health
• How a moderate overnight fasting window may fit into a healthy lifestyle
• Why fasting strategies should be individualized rather than approached with a one-size-fits-all mindset
About the Guests
William Hsu, MD, is an endocrinologist and Chief Medical Officer of L-Nutra. His work focuses on metabolic health, nutrition technology, fasting research, and integrating nutrition-based interventions into healthcare.
Ashley Bizzell, MS, RD, is Director of Clinical Nutrition at L-Nutra Health. She has more than 15 years of experience as a registered dietitian and works with nutrition and lifestyle strategies designed to support metabolic health.
Resources Mentioned:
L-Nutra Health
Learn more about Thrive's nutrition-centered primary care and functional nutrition services:
thrive-clinics.com
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Medical Disclaimer
This podcast is for educational purposes only and is not a substitute for individualized medical advice, diagnosis, or treatment. Fasting is not appropriate for everyone. If you take insulin, glucose-lowering medication, or other medications affected by changes in food intake, or if you have a medical condition, are pregnant or breastfeeding, have a history of an eating disorder, or have other nutritional concerns, consult your healthcare provider before beginning a fasting protocol.
Brief Episode Summary
Erin Skinner talks with Dr. Hsu about fasting, autophagy, and metabolic health. Learn how fasting-mimicking diets differ from time-restricted eating, how fasting may support cellular health, and why nutrition and adequate protein still matter for long-term health.
