Welcome to the Huberman Lab Podcast, where we discuss science and science -based tools for everyday life.
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine.
My guest today is Dr.
Stacey Sims. Dr. Stacey Sims is an exercise physiologist and a nutrition scientist and a world expert in all things training and nutrition, specifically for women.
In addition to working at Stanford and with numerous professional athletic teams, Dr.
Sims has authored more than 100 peer -reviewed studies on exercise physiology.
She has not only evaluated existing protocols for nutrition and fitness that are specific to women versus men, but she has also developed many new protocols that are now in practice with professional sports teams but that can also serve people who are generally interested in fitness and longevity and,
in doing so, the general public.
The tools that Dr. Sims shares with us today are applicable to fitness, to changing your body composition and to overall health.
Today we discuss how hormones and hormone cycles impact nutrition and fitness needs specifically in women of different ages.
We of course discuss the menstrual cycle, perimenopause and menopause, but also female -specific nutrition and training as it relates to things independent of hormones.
For instance, we evaluate the evidence that women may not want to train fasted and the reasons for that.
We talk about how training might vary according to different phases of the menstrual cycle and we discuss how women can design nutrition and training programs that are optimized for their specific needs, not just because they are women, but because they are women of a particular stage of life and women
with particular goals.
As you'll soon see, Dr.
Sims is exquisitely skilled at explaining the human universals of nutrition and training, that is the things that do not differ between men and women and their needs in terms of nutrition and training.
But she is also exquisitely skilled at highlighting the data showing that there are specific areas of nutrition and fitness for which women and men differ and women have specific needs.
So today you will learn what those are and you will learn how to apply those specific protocols such that by the end of today's episode you will be armed with a tremendous amount of new knowledge about the biological mechanisms and the specific dos and do nots that can guide you towards your female
specific health and fitness goals.
Before you begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford.
It is, however, part of my desire and effort to bring zero cost to consumer information about science and science related tools to the general public.
In keeping with that theme, I'd like to thank the sponsors of today's podcast.
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And now for my discussion with Dr.
Stacey Sims. Dr. Stacey Sims, welcome.
Thanks. Our podcast and I put out a lot of content about nutrition, fitness, cold exposure, heat exposure, hydration, topics that are very near and dear to your heart and for which you have a ton of expertise, but for which you have an extra degree of expertise as it relates to females specifically.
Yeah, so I'm excited to talk to you today because very often I will get questions in the comment section on social media or on YouTube.
Was this study done in both men and women?
How does it differ for men versus women and on and on?
And I rarely, if ever have answers, but you have answers.
I have answers for you.
So just to kick things off because this is a question I get really often, fasting.
Oh yeah. Intermittent fasting.
We need to distinguish between the two, of course.
Perhaps the most common question I get as it relates to males versus females is, is intermittent fasting or time restricted feeding, as it's sometimes called, an eight hour feeding window, a six hour feeding window, a 10 hour feeding window.
Is that something that perhaps differs in terms of its impact and how well it works for men versus women?
Yeah, that's the short answer.
Great. Yeah. So I'll put some parameters around it.
Right. So if we talk about intermittent fasting, that's where you have like the, if you were to actually pay attention to your circadian rhythm and fuel, according to the stress at hand and knowing that you're going to garner less stress that way.
And if we're really tying in nutrition, according to that profile, instead of following a fast, we see better brain improvements as well.
We see more cognitive function.
We see less thyroid dysfunction.
And overall, a woman does much better when we're not in that fasted state.
Then when you look at population research that's coming out now, they're showing in both men and women who hold their fast till noon and then have an eating window from noon to maybe 6 p .m., have more obesogenic outcomes than people who break their fast at 8 and finished their eating window by 4 or 5
p .m. So it's coming back to the chronobiology of we need to eat when our body is under stress and needs it, unless we have a specific issue like obesity inactivity, PCOS or other metabolic conditions.
Then we can look at using fasting as a strategic intervention to help with those modalities.
Super interesting. Two questions.
Is there a protective effect of starting the eating window?
And here I'm asking for both men and women starting the eating window at, say, 11 a .m.
or noon and ending it a little bit later.
So not a six hour eating window or seven hour eating window, but extending that to eight or nine p .m.
Under those conditions, do you still see the obesogenic effect?
Yes, because we're looking at the way cortisol responds.
We know cortisol has lots of fluctuations throughout the day.
And it peaks about half an hour after you wake up.
Right. So if you're having that cortisol peak half an hour after you wake up, but you're not eating, then that is that higher baseline sympathetic drive for women.
For men, it's not the same.
So when we're looking at that obesogenic outcome, the actual timing hasn't been tested yet to see how can we expand or contract that eating window for men.
But for women, because of that cortisol peak that right after waking up, women tend to be already sympathetically driven.
So then they walk around more tired but wired and have a really, really difficult time accessing any kind of parasympathetic responses down the way.
Where if you have something really small where you're bringing blood sugar up, then it's signaling to the hypothalamus, hey, yeah, there's some nutrition on board.
Then we can start our day.
So again, it has to look at that circadian rhythm and those hormone fluxes, which people don't really either understand or talk about because all of our hormones flux through the day.
And so you have to look at where's the peak of cortisol, how does estrogen flux, how does luteinizing hormone flux progesterone, all of these things that have this tight interplay, and the more we're doing the hormone research and the more we're understanding these perturbations and how important it
is to figdala that happens with oral contraceptive use.
It's reversible in adults, but for young girls, we don't know because their brain is developing.
And unfortunately, physicians will pass out OCs as if it's candy or a contraceptive.
And do you recall what the direction of the effect was on the amygdala for those that don't recall the amygdala bilateral brain structure, meaning one on each side of your brain, literally means almond in Latin.
It's almond shaped and it's part of a larger network associated with threat detection.
Sometimes it's described the locus of fear in the brain, but it's involved in a lot of other things, too, both positive valence and negative valence, but nonetheless is part of the threat detection system, elevated levels of arousal, which is why it's often discussed in the context of fear, anxiety,
etc. It increased fear in women who are on the OC or a contraceptive pill, made them less willing to take chances.
And when they went off it, they're like, well, why couldn't I do that before?
So that's why they started looking at the amygdala.
And when I say we're looking at young girls and again, we don't know what's happening, is it reversible in young girls that are put on it or not because of the brain structure changes that are happening.
So when we talk about an oral contraceptive pill, I want people to understand that it has a significant effect on the body, not just reproductive.
We don't know enough about all the other effects.
So I have parents who say my daughter wants to go on the oral contraceptive pill.
She's having irregular periods.
She's an athlete. We want to be able to control it.
And it's like if there's a issue with your menstrual cycle, now it's still going to be there when you get off it.
So we have to look and see what what's going on here.
If you're looking to get on it to control your menstrual cycle, why?
Because we know that you can have an increase in your VO2 max and other anaerobic capacity when you are not on it.
So you have a better top end capacity when you're not being blunted by these hormones.
And then the other conversation is, oh, my skin is like, well, they have really good dermatologists that can help you with that.
You don't have to go on an oral contraceptive pill, but unfortunately, GPs don't understand all of that.
And if a girl comes in and says, I'm having irregular cycles, heavy menstrual bleeding, I want to go on the OC.
Here you go. So it is a huge conversation still we had.
I put it in the same category as menopause hormone therapy, because there isn't enough research to address all the population needs.
And we see these big pendulum switches.
So before it was like, everyone beyond the OC.
And now it's like, maybe not.
And then it was no one beyond menopause hormone therapy.
Everyone should be on it.
But we need to land in the middle and understand more of what's happening with these exogenous hormones.
Is there any evidence that other forms of female contraception can be, let's just say problematic for the types of things we're discussing today?
Like the implant and the depot.
Or IUD, copper IUD.
Copper IUD and the marina or you know, your progestin laced IUD, those are what a lot of my tactical athletes will use because it doesn't have a systemic effect on adaptation or inflammation, mood, any of those things.
And it's a fit and forget.
So you can put it in for up to three to five years.
If you have a really heavy bleeding, it really dissipates because the whole idea of an IUD is that then the endometrial lining.
And so then you have a topology that takes care of the endometrial lining.
So you don't necessarily have a bleed.
The copper IUD is different because you do have really heavy bleeding for the first three cycles and then it attenuates.
Before we got started today, you mentioned some very interesting pioneering studies on evaluating menstrual blood itself as a window into some larger themes about what's going on physiologically, maybe even psychologically.
Now might be a good segue to just touch into that.
We can always return to it again later.
But let me just ask it more directly.
What are some things that can be measured directly from menstrual blood that are informative for women?
And it sounds like there's a new generation of at -home tests that might be interesting and informative for them to think about.
Yeah. Well, if you think about menstrual fluid, everyone thinks about it as a discard product, but it's a very good indicator of what's happening from an endocrine standpoint.
It gives a really good indication of what's happening from an endometrial standpoint.
So if you're looking at all the cytokines and the proteins and the tissue that comes from it, it's a huge indicator that's naturally discharged that we're now looking at for determining HPV.
Do you have it or not?
What about proteins for PCOS?
Can we really identify PCOS or endometriosis?
We talk about PCOS for a moment.
Most people have heard of it by now, but polycystic ovarian syndrome, it's associated with typically elevated androgens.
It's becoming more and more common or perhaps detected more based on better detection methods.
I don't know which.
The prevalence of PCOS seems to be very, very high.
It does. And I think it's a combination of both.
We also see some rebound PCOS that happens when someone gets off an oral contraceptive pill.
It's not necessarily true PCOS because what's happening now?
Your ovaries are producing eggs that have been downregulated for so long.
So under ultrasound, it might look like PCOS, but it's not necessarily true indication.
The other is more and more women are starting to eat more.
And so they're coming out of low energy.
Can I add a second blood test at a different phase of the menstrual cycle?
Where would you place that second test?
Day two of the menstrual cycle second day of bleeding to get a really good indication of what your true estrogen level is at baseline.
And if she measures her hormones at those two times within the cycle, do you think that's sufficient to get 75 % plus of the relevant data?
Yeah, definitely. Terrific.
Caffeine. Yes. In the old days, meaning when I was a kid and not long ago, 10 years ago, three weeks ago, we would hear these crazy statements about caffeine.
It pulls calcium out of the bones.
You'd hear this stuff.
I did a whole episode on caffeine.
I'm a big fan of caffeine, but I do warn people that if they suffer from anxiety or they're going through a particularly stressful life event, it can raise the activity of the sympathetic arm of the autonomic nervous system.
You'll feel more nervous.
You're more prone to panic when you're drinking caffeine.
But many people love caffeine.
I think 90 % of the adult population of the world ingest some form of caffeine every single day.
I'm in that 90%. Likewise, making it the most consumed drug worldwide.
Is caffeine safe for women?
I suspect based on what you just said that the answer will be yes.
But are there case conditions where women should be cautious about their intake of caffeine independent of this anxiety thing?
I mean, people probably shouldn't drink more caffeine than they can tolerate psychologically.
No one. Male, female, young or old.
Yeah. It's more of a genetic factor than it is a sex factor.
So I mean, both men and women will be fast metabolizers, slow metabolizers, or not have an effect that becomes the bigger rock of them.
What we do find is in that perimenopausal state, women will become more sensitive to the blood sugar fluctuations that happen with caffeine.
So they're used to having coffee in the morning and with something then halfway through their workout, they become a little bit hypoglycemic.
Because there's changes in insulin sensitivity, insulin responses.
So there's changes also in blood sugar control and caffeine can exacerbate that.
So if you are someone who's like, oh, I always have a double espresso before I go work out.
And then halfway through, I'm really hypoglycemic.
I'm really dizzy and lightheaded.
I don't know what to do.
Feel sick or nauseous.
Eat some food with it.
What about sipping caffeine through the workout?
You know, taking that coffee in and just having a sip between sets.
Can that offset some of that?
I don't think so. Okay.
I hear a lot that people who drink caffeine before a workout, you know, midway through, they're like, I don't feel good.
Yeah. Because they don't eat.
For me, that just stimulates the desire for more caffeine, but we're even.
