The Diary Of A CEO with Steven Bartlett
Women's Fertility & Lifestyle Debate: Dangers Of Not Having A Period! Fasting Can Backfire For Women
16 Oct 2025
Chapter 1: What are the consequences of an irregular menstrual cycle?
If someone's menstrual cycle is irregular, should they be concerned? Yes.
Yes. Yes. Your body's meant to work like clockwork. And our monthly cycle is so much more than getting ready to have a baby. Especially when we're looking at exercise.
And it's important to say, if you don't have a period, it's very harmful to long-term health. Brain health. Mental health. Low energy. Mood. And libido. And I don't want the younger generations to have to go through the stuff that we've gone through. So it's an important discussion that we need to have.
We are joined by four leading female health experts from very different fields to have a crucial conversation about women's health.
With over 80 years combined experience, they're sharing the truth about what every woman and every man needs to hear.
We asked 1,000 women to submit their questions ahead of this conversation, and I got so many questions around fertility, understanding hormones, PCOS, birth control pill, miscarriage.
And I'll say this, Stephen, it's because we haven't had these discussions publicly. When we look at funding in women's health, it's horrible. Like less than 1% is spent on women over 40.
Women are living 20% more of our lives with chronic disease or mental health disorders.
I mean, 50% of patients with unexplained infertility have endometriosis. But yet it takes women 7 to 10 years to get a diagnosis after symptoms start. But also there are things that we do that will inherently harm our fertility because we're not taught this. And it predisposes you to many medical problems later in life. And patients will say, I have a really high pain tolerance. Yes.
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Chapter 2: Why is there a research gap in women's health?
This is a scary statistic. So... Oh, my God.
It's crazy.
I just think it's insane. This is why we need to create change.
This might be one It's probably never going to be the case again that these four individuals that are at the very top of women's health in their fields will be in the same place at the same time having this conversation. We structured this conversation into two parts. They cover completely different subjects, but they're fundamentally interlinked.
For me, the understanding that I got from this conversation at this table with these four women has fundamentally changed my life. It's going to change how I deal with my romantic partner, my sister, my team members that I work with every single day. And funnily enough, because it's a conversation I wouldn't have clicked as a man, it turned out to be the conversation that I needed the most.
And I don't think I've ever said this before, but if there was ever an episode to share with a loved one, then this is that episode. Please share this episode with as many women as you can, but also with as many men as you can. Ladies, we should start with some introductions.
Could you give me a brief introduction, Stacey, as it relates to your perspective and your experience and what your sort of bias is as it comes to this debate? When I say bias, I mean your experience and your research that you're lending to this conversation today.
I come from the exercise, phys and sports med background.
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Chapter 3: What does a normal menstrual cycle look like?
So I'm always looking through the lens of activity and nutrition and how that has impact on our stress and our stress outcomes and how we can adapt to specific applied stressors. especially when we're looking at improving health span, improving mood, improving body composition, all of those things. I've worked with and still work with the subset of active women.
I come from an endurance and a high-profile, high-performance sport background. So that's where I've gotten my chops and then brought it over into the general recreational female athlete kind of perspective.
Natalie?
I'm a fertility doctor, and every day I help patients with IVF get pregnant because I have an IVF clinic.
But my big passion has always been natural fertility after I experienced my own pregnancy losses, trying to understand how we interact with the world and how that changes our hormones and help women understand what their hormones are, what natural fertility is, what happens as we age to our bodies, our eggs, and our hormones, and let them be better stewards of their own fertility and their own health decisions.
Mary?
I have a background in general OBGYN, so I'm considered to be a women's health specialist. And it wasn't until I kind of went through my own menopause that I realized that there was significant gap in my training.
You know, hearing, watching Dr. Sims on, I think, your podcast talking about how women are not little men really struck such a chord with me and made me realize I was siloing women's health to the reproductive organs, the breasts, the uterus, the ovaries, the vagina.
And that if I really did wanted to make a difference in a woman's whole health life, this last 30 years, 30, 40 years of her life, I needed to refocus what we were thinking about women's health for the long term. So I come from a background in academics. I was a professor for 20 years.
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Chapter 4: How can lifestyle choices impact hormonal health?
And what they found was, yes, we live longer. We've all known that. However, we have twice as high of mental health disorders. We're two times as more likely to end up in a nursing home. We are much more likely to lose our long-term independence from frailty or dementia, much more than our age-matched male counterparts. And that's, I think, what we're all trying to fight here.
Yeah.
And diseases that impact women specifically and only, things like PCOS, endometriosis, are extensively underfunded and not researched. It takes women 7 to 10 years to get a diagnosis of endometriosis after symptoms start. And we know this is a disease that impacts your entire body in addition to your fertility. But women are dismissed. They're not taken seriously.
And there's not research guiding what we can do in a lot of these situations to try to help them the best.
Why isn't the research there? Why don't they research if women are the majority of the population? Why is all the funding going to researching men?
You have to think about who was in the room when medicine and science first started. So if you think about back when the Industrial Revolution and the modernization of what we know as medicine, women were pushed out because they were believed to have smaller brains, thanks to Darwin, and not thought to have a seat at the table. So when you're thinking about designing studies, it was...
pretty much designed on the male physiology, on the male body, and then women were an afterthought. So there wasn't any real in-depth look of, well, women are different from birth or in utero, XX is different from XY. So all the research has just been generalized to women, even things like aspirin for heart attacks and thinning blood.
Eighth inhibitors.
Yeah, all of this was done on men and then just generalized to women. And now that we're having this global conversation on women's health, people are like, well, where is the information specific for women? And there's just a very small subset. So we're looking and trying to expand that, but we have a lot of catching up to do.
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Chapter 5: What are the implications of hormonal changes during the luteal phase?
That's still a very effective way to use the pill. But because women don't love having periods, we've offered these other options, which are not – wrong, but they just have a bigger consequence downstream than we're talking about. But the pill is very short-acting. It only has a half-life of 28 hours, meaning it is out of your body very quickly.
So you do want to stop the pill and see what is happening and track your cycles. That is something nice about it versus an implant or an IUD that is— The fit and forget. The fit and forgets that people like.
Yeah, the fit and forgets.
Yeah, the question that came in from the 1,000 women we spoke to in the Diary of a Serial audience was, is there any way to control hormonal mood swings during the luteal phase of the menstrual cycle, which I now know is the second phase of the menstrual cycle.
Stephen, you've learned so much.
Yes.
That's great. I love that. In the luteal phase, we do tend to see more mood changes and physical changes. And a lot of this is because we have an increase in estrogen and progesterone and then a decrease in both of these hormones. And what we find is that some women are simply more sensitive to these changes. They feel them quite profoundly.
And there's even something called PMDD, premenstrual dysphoric disorder, which is when those hormones are dropping, you get these terrible mood swings, this terrible depression and anxiety.
In addition to physical changes with terrible fatigue, you just feel like you can't accomplish any of your tasks, insomnia, quite similar to a lot of the things that we talk about anytime we talk about a low estrogen state. Right, right.
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Chapter 6: How can lifestyle changes impact hormonal balance and fertility?
I'm going to take some estrogen, helping alleviate these symptoms without interfering with ovulatory function.
But I was trained to give them an SSRI for those 7 to 10 days.
An antidepressant pill.
Yes, an antidepressant. Only for those two weeks. Seraphim, was that the brand name of it? And it does tend to help. But what no one taught me and what clinical experience has taught me and talking to all these other smart people is a low-dose estrogen. Treating the root cause. Treating the root cause. Just give her estrogen back during that time period and she gets remarkably better.
In some of the nutrition research, finding that low iron and low vitamin D are huge contributors to it. So there's that research to investigate too, which is interesting because there are some women also who don't want to go on SSRI or estradiol.
The Endocrine Society does not recommend routine testing of vitamin D. It's crazy. I just think it's insane.
With my partner, I should anticipate that her mood might drop in the lead up to having her period.
It's very common.
And then after her period, it might recover.
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Chapter 7: What are the signs and symptoms of perimenopause?
Her brain starts by, from a reproductive hormone level, the brain starts by sending out FSH, follicle stimulating hormone, which is going to get her ovary to start growing an egg, which lives inside a follicle and making estrogen. And that rise in estrogen as it's growing will stop her from bleeding. So at the beginning, that cycle day one,
The bleeding that she's experiencing or her period is because she didn't get pregnant in the month before. So it's getting rid of that endometrial lining, cleaning the slate. She's estrogen and progesterone low during that time period. And then once her bleeding stops, it's because an egg has been chosen. Estrogen is then going to rise until it gets to that peak level.
During that time, she's going to feel her best for most women.
So is that the first 14 days?
By convention, if you had a 28-day cycle, which only about 13% of women actually do, but all of these graphs, if you look at, usually use 28 days because it's easy to go week by week. And that's the lunar calendar.
Yeah.
So we see that, but we have to acknowledge that most women don't have a 28-day cycle. But it is roughly the first two weeks for most women to get up to that ovulatory time period. So the time from I have started bleeding until I am now ovulating, that is all considered the follicular phase.
And on this little image that I have in front of me here, it says in those first 14 days, she's going to have better spatial skills and be more anxious.
So once you get to your estrogen dominant, so you have a lot of estrogen and you don't have progesterone, most women have increased concentration. They have more focus. They actually can sleep better. They have higher libido. You feel like your performance, even for athletes, performance tends to be improved. More aggression, more concentration, more, yeah.
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Chapter 8: How does menopause affect mental health and relationships?
Well, progesterone slows your body's metabolism down. It's preparing you for that pregnancy. Calmer is a nice way to put it. But essentially, your metabolic rate is going to change. Your body is going to shift how it functions. Many women actually have fatigue. They're hungry.
Specifically in the brain, progesterone levels, as they rise, we see an increase in GABA, which is a neurotransmitter, one of our brain hormones that jumps between one neuron to the other. And that is more of a calming hormone. So women tend to—we see sleep changes. You see deeper sleep, longer sleep in that luteal phase.
Right.
And on this it says she's going to be horny at day 14. I don't know how else to say it.
Because she has an egg available. That's that peak estrogen. That estrogen level of 200 picograms is heightening everything to have peak libido when an egg is released. The body is made that way on purpose.
This is a bit off script, but my girlfriend always talks about her HRV being very different. And so she has really great HRV scores. And then once every month for a period of time, they're terrible and she can't explain it.
So this is where wearables come into play. Yeah. So wearables are not designed to capture women's physiology. So what happens after ovulation is your respiratory rate goes up, your resting heart rate goes up, and your HRV plummets. So on the wearables, most women about five days before their period start will never be in a
the clear so to speak they will never look recovered they will never look like they can take on a lot of stress they're not stress resilient because of the way the algorithms are reading this change that is natural that is produced by progesterone to alter our respiratory rate and our heart rate it doesn't mean that she's not stress resilient is what the wearable is saying
Ah, because she came downstairs and she said, oh God, my recovery is so bad. And then I think a couple of days later, a little while later, she had a period. I'm not sure. I can't remember the timeframes, but she came downstairs and she was like shocked. She'd done everything right. But her recovery on her wearable said that she was in terrible state.
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