July 11, 2025
Episode 466: Dr. Stacy Sims: Why Women Can't Fast Like Men + The Training Intensity You Should Avoid
Habits and HustleAbout this episode
Why do women struggle more with intermittent fasting than men? And what's the real secret to building bone density that most women are missing? In this Fitness Friday episode, exercise physiologist Dr. Stacy Sims and I break down the biological differences that make popular health trends work differently for women. We explore the concept of "polarized training"—why women need to go super hard or super easy, avoiding that moderate-intensity middle zone that can actually increase cortisol and visceral fat. We also discuss the fascinating brain differences between men and women that make fasting potentially harmful for women's hormones, sleep, and body composition. Dr. Stacy Sims is an international exercise physiologist and nutrition scientist who specializes in sex differences in training, nutrition, and environmental conditions. She's the author of "Roar" and "Next Level" and has spent decades researching how women's unique physiology requires different approaches to health and fitness. What we discuss: The polarized training approach: why moderate intensity is the enemy Minimum effective dose for women's training (hint: it's less than you think) Why jump training beats running for bone density The specific type of jumping that builds bones (it's not what you expect) Why trampolines don't count for bone building The brain differences that make fasting risky for women Why women become "anabolically resistant" at 40 and need more protein The top 3 supplements every woman needs Thank you to our sponsor: Momentous: Shop this link and use code Jen for 20% off Therasage: Head over to therasage.com and use code Be Bold for 15% off TruNiagen: Head over to truniagen.com and use code HUSTLE20 to get $20 off any purchase over $100. Magic Mind: Head over to www . magicmind.com /jen and use code Jen at checkout. Bio.me: Link to daily prebiotic fiber here , code Jennifer20 for 20% off. David: Buy 4, get the 5th free at davidprotein.com/habitsandhustle . Find more from Dr. Stacy Sims: Website: https://www.drstacysims.com/ Instagram: https://www.instagram.com/drstacysims Find more from Jen: Website: https://www.jennifercohen.com/ Instagram: @therealjencohen Books: https://www.jennifercohen.com/books Speaking : https://www.jennifercohen.com/speaking-engagements