Episode 466: Dr. Stacy Sims: Why Women Can't Fast Like Men + The Training Intensity You Should Avoid

Habits and Hustle

Jen Cohen and Habit Nest

Education, Health & Fitness, Business, Self-improvement, Entrepreneurship

4.4 • 763 Ratings

🗓️ 11 July 2025

⏱️ 20 minutes

🔗️ Recording | iTunes | RSS

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Summary

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

Transcript

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0:00.0	Hi, guys. It's Tony Robbins. You're listening to Habits and Hustle. Crush it.
0:06.5	Hey, friends, you're listening to Fitness Friday on the Habits and Hustle podcast where myself and my friends share quick and very actionable advice for you becoming your healthiest self. So stay tuned and let me know how you leveled up.
0:28.6	Before we dive into today's episode, I want to thank our sponsor, Momentus. When your goal is
0:34.6	health span, living better and longer, there are very few non-negotiables.
0:40.3	One of them, quality.
0:42.4	And when it comes to supplements designed for high performers, nobody does it better than Momentus.
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0:59.9	And that's why they're trusted by all 32 NFL teams and top collegiate sports dietitians
1:06.2	across the country.
1:07.6	Here's the thing.
1:08.6	They don't sell every supplement under the sun because they
1:11.8	believe in nailing the basics with rock solid consistency. And those basics are protein and
1:19.0	creatine. Momentous sources creopure. The purest form of creatine monohydrate available, an absolute
1:26.5	must for both men and women who want peak
1:29.8	physical and cognitive performance. So if you're serious about leveling up, go to livemomentous.com
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1:52.9	Women underestimate recovery all of the time. So polarized beans that you're staying out of that
1:58.8	middle zone. So you can go super hard when you need to and you recover super easy.
2:03.6	So we look at the moderate intensity stuff as it's too hard to be easy and it's too easy to be hard to invoke change.
2:10.3	Stay out of that.
2:11.4	You want to be hard to invoke change and you want to go easy to recover so that you can go hard again.
	...

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