Episode 387: Nathan T. Jenkins on Metabolic Flexibility, Aerobic Base, and First Principles

In this episode of the Flex Diet Podcast, I sit down with Dr. Nathan Jenkins to discuss how to improve performance, body composition, and long-term health through the lens of aerobic development and metabolic flexibility.

Nathan shares his journey from exercise physiology and coaching CrossFit athletes to his new role teaching physiology at the University of Georgia School of Medicine. We discuss why metabolic flexibility is such a powerful framework for understanding everything from biochemistry and exercise performance to metabolic disease.

We also dive into interpreting maximal exercise testing data, including VO₂ measurements, EKG analysis, and near-infrared spectroscopy (NIRS), along with how different energy systems work together during training and competition. Nathan explains why building an aerobic base is critical for repeated high-intensity performance, how pacing impacts outcomes, and why the ability to "suffer" is actually a trainable skill.

To wrap up, we cover practical strategies you can apply right away, including prioritizing protein and carbohydrates, improving sleep quality, and addressing common micronutrient deficiencies through blood work, such as magnesium, vitamin D, and omega-3 status.

Sponsors:

• Daily Fitness Insider Newsletter: https://flex-diet.kit.com/bfa1510fa8

Available now:

• Grab a copy of the Triphasic Training II book I co-wrote with Cal Deitz here.

Episode chapters:

• 02:47 Meet Dr Nathan Jenkins
• 04:38 CrossFit Nutrition Reality Check
• 07:09 Leaving Tenure for Family
• 09:21 Back to Academia and Med Ed
• 11:29 Why Exercise Physiology Matters
• 14:36 Stress Tests Reveal Pathology
• 18:19 Max Testing and NIRS Setup
• 22:42 Raw Data Over Machine Outputs
• 24:18 Bohr Effect and Oxygen Delivery
• 28:09 Energy Systems in the Real World
• 33:05 Coaching Basics That Matter
• 35:40 Teaching Cardio From First Principles
• 36:36 Aerobic Base Reality Check
• 37:19 Cardio for Meatheads Pitch
• 39:13 CrossFit Endurance Breakthroughs
• 41:49 Fixing Time Domain Weakness
• 45:46 Pacing Like Froning Fraser
• 48:42 RAAM Gamesmanship Story
• 51:45 Pain Management Truths
• 53:23 VO2 Max Feels the Same
• 55:54 Suffering as a Skill
• 59:09 Cold Plunge Mindset Study
• 01:00:52 Caffeine Placebo and Belief
• 01:03:22 Heat Acclimation and 10K Prep
• 01:04:36 Metabolic Flexibility Lens
• 01:08:16 Teaching Diabetes Integration
• 01:10:56 Bloodwork Meets Flexibility
• 01:12:37 Where Fat Goes Wrong
• 01:15:07 Sustainable Deficit Strategy
• 01:16:34 Four Priorities Blueprint
• 01:17:21 Protein and Carb Targets
• 01:21:08 Sleep and Micronutrients
• 01:27:06 Omega-3 Testing Nuance
• 01:29:36 Wrap Up and Next Steps
• 01:31:52 Newsletter and Flex Diet Cert
• 01:33:20 Final Thanks and Subscribe

Flex Diet Podcasts you may enjoy:

• Episode 344: Metabolic Adaptations, Lactate, and Training Smarter with Dr. Phil Batterson
  • YouTube: https://youtu.be/PPZyO1nxSPA
• Episode 383: Body Composition, Strength Training, and Sustainable Habits with Martin Silva
  • YouTube: https://youtu.be/p8oM0gW488U

Connect with Dr. Jenkins:

• Website: https://www.drnathanjenkins.com/
• Instagram: https://www.instagram.com/drnathanjenkins

Get In Touch with Dr Mike:

• Instagram: Drmiketnelson
• YouTube: @flexdietcert
• Email: Miketnelson.com/contact-us

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