The Ultimate Human with Gary Brecka
128. Kristen Holmes: The TRUTH About Women's Fasting Windows (Science Says You're Doing It Wrong)
Thu, 02 Jan 2025
Most women are told that narrower eating windows = better results, but according to Whoop’s Global Head of Performance and Science Kristen Holmes, this common advice is causing more harm than good — especially for women’s hormones. In this short episode, Kristen Holmes breaks down the science behind circadian rhythms, metabolic health, and the crucial connection between eating patterns and the menstrual cycle. What eating window works best for your body? Share your experience in the comments below, and join the conversation about women’s health and nutrition timing! Connect with Kristen Holmes: Website: https://bit.ly/4fAFT5m Instagram: https://bit.ly/41MYiIK TikTok: https://bit.ly/3Ph0qRx LinkedIn: https://bit.ly/3ByxiCl 00:00 Intro of Show 02:10 Eating Window during Menstrual Cycle 06:14 Impact of Food or Alcohol on Stress 07:57 Benefits of Circadian Alignment 10:36 An Average American is Eating in a 15-Hour Window 12:20 Mental Clarity Achieved from Fasting 13:16 Time-Restricted Eating and Hormones WHOOP - GET 1 FREE MONTH WHEN YOU JOIN!: https://bit.ly/3VQ0nzW BODY HEALTH - USE CODE “ULTIMATE20” FOR 20% OFF YOUR ORDER: http://bit.ly/4e5IjsV BAJA GOLD - 91 ESSENTIAL MINERALS PER PINCH! 10% OFF USE CODE "ULTIMATE10": https://bit.ly/3WSBqUa EIGHT SLEEP - SAVE $350 ON THE POD 4 ULTRA WITH CODE “GARY”: https://bit.ly/3WkLd6E ELEVATE YOUR WORKOUTS WITH THE ULTIMATE HUMAN STRENGTH TRAINING EQUIPMENT: https://bit.ly/3zYwtSl COLD LIFE - BOOST RECOVERY & WELL-BEING WITH THE ULTIMATE HUMAN PLUNGE: https://bit.ly/4eULUKp MASA CHIPS - GET 20% OFF YOUR FIRST $50+ ORDER: https://bit.ly/40LVY4y PARKER PASTURES - GET PREMIUM GRASS-FED MEATS TODAY: https://bit.ly/4hHcbhc HAPBEE - FEEL BETTER & PERFORM AT YOUR BEST: https://bit.ly/4a6glfo GET GARY’S WEEKLY TIPS ON HEALTH AND LIFESTYLE OPTIMIZATION: https://bit.ly/4eLDbdU SHOP GARY’S TOP-RATED PRODUCTS & EXCLUSIVE DEALS: https://theultimatehuman.com/amazon-recs Watch the “Ultimate Human Podcast” every Tuesday & Thursday at 9AM EST on YouTube: https://bit.ly/3RPQYX8 Connect with Gary Brecka: Website: https://bit.ly/4eLDbdU Instagram: https://bit.ly/3RPpnFs TikTok: https://bit.ly/4coJ8fo Facebook: https://bit.ly/464VA1H X.com: https://bit.ly/3Opc8tf LinkedIn: https://bit.ly/4hH7Ri2 SUBSCRIBE TO: https://www.youtube.com/@ultimatehumanpodcast https://www.youtube.com/@garybrecka Download the “Ultimate Human Podcast” on all your favorite podcast platforms: https://bit.ly/3RQftU0 The Ultimate Human with Gary Brecka Podcast is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this podcast or materials linked from this podcast is at the user’s own risk. The Content of this podcast is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard or delay in obtaining medical advice for any medical condition they may have and should seek the assistance of their health care professionals for any such conditions. Learn more about your ad choices. Visit megaphone.fm/adchoices
Chapter 1: What is the average eating window for Americans?
The average American is eating over the course of 15 hours.
Chapter 2: How does the menstrual cycle affect women's fasting?
It was astounding to me.
It puts a lot of stress on our system. Like digestion is effortful. That's why your sleep is so messed up because your body's having to prioritize digestion. So all the restoration and repair that should be happening like has to basically take a backseat while we digest.
Chapter 3: What are the benefits of circadian alignment in eating?
Sometimes the women that have the most narrow feeding window have the highest level of hormone disruption.
Chapter 4: What happens when women adopt narrow eating windows?
These really narrow eating windows put a lot of stress on the body. When people restrict their feeding window to 10 hours, they have better markers of sleep and better markers of recovery, regardless of what phase of the menstrual cycle they're in. Fueling for your activities, to me, is the principle that all women need to be thinking about.
Chapter 5: How does fasting impact women's hormones?
I'm really excited to hear what comes out of your research with WHOOP. If I was to hypothesize, we're gonna see the big data at WHOOP support what we're seeing in lab values and whatnot for women.
Chapter 6: What role does food have on sleep quality?
I think there isn't a lot of research on
Chapter 7: What is the ideal eating window for women?
Hey guys, welcome back to the Ultimate Human Podcast, where we go down the road of everything anti-aging, biohacking, longevity, and everything in between. Kristen Holmes, who's been on the podcast before, came back for a short, because we just thought it was so important to do a short anecdotal review of our discussion on time-restricted eating and the female menstrual cycle.
Chapter 8: How does food timing affect metabolic health?
She's working on some really interesting things at Whoop, which aren't ready for public dissemination yet, but using big data to look at how wearables can actually track the menstrual cycle in women and may be a potential alternative to birth control. And then we started to go down the road of time restricted eating. So I hope you enjoy this short podcast with Kristen Holmes.
One of the things I have been trying to do is increase the appeal to my female audience and not just get more women on to the podcast, but talk more about women's issues, things that are important to women that the biohacking space is sort of negating. And we started talking about time-restricted eating, and we have noticed in our clinical setting that...
Sometimes the women that have the most narrow feeding window have the highest level of hormone disruption. And very likely, according to our OBGYN, it has a lot to do with they can eat differently during different parts of the menstrual cycle. So if they wanted to sort of like accordion expand and contract their feeding window, which is a little difficult to do,
But a lot of these young women that just adopt strict intermittent fasting and they're very militant about it, their hormones go into a tailspin. Again, it's anecdotal, but we find quite a few of these women have this issue.
And I think there isn't a lot of research on women and intermittent fasting. A lot of the research is in men. So there's still so much more that I think we have to do. But I do think a lot of the women, a lot of the researchers in this space would say that these really narrow eating windows put a lot of stress on the body.
And especially during the luteal phase, for example, the couple weeks leading into menses, your body is already working really, really hard. It's a metabolically super expensive time. So when we're layering on other stress, we're intermittent fasting, we're exercising, we're doing cold plunge, we're doing sauna. When you've got all these stressors, like you are...
basically asking your body to do, you know, Herculean kind of level type of work, right? It's just unnecessary, right? So I think, again, given that the research isn't quite there yet, I think there is a case to be made that during the luteal phase, not a time to have a really narrow eating window. And just to clarify...
the way I interpret the literature, there's intermittent fasting, which basically has a caloric restriction component. And then there's time-restricted eating, which has a circadian component. And I'm not a nutritionist and I'm not an expert in fasting, but my PhD was in circadian alignment, predicts psychological and physiological resilience. So I spent a lot of time on circadian things.
And I have seen in the data, When people restrict their feeding window to 10 hours, they have better markers of sleep and better markers of recovery, regardless of what phase of the menstrual cycle they're in. So there is, I think, a sweet spot. And it looks like it's about 10 hours where we're eating. And then we're fasting the other 14 hours. And that's where people call it fasting.
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