drtalks logo.png

Intermittent Fasting Transformation

Video Thumbnail


Play Button
  • Hormone balancing related to intermittent fasting; including less common ones such as Leptin, Ghrelin, DHEA, and Cortisol
  • Signs that intermittent fasting is not working for you
  • How to eat to maximize fasting success
  • What are the different types of fasting and why is the 16:8 fast a good starting point
  • How to fast for your cycle vs. non-cycling and perimenopause/menopausal women
  • What is metabolic flexibility and how does this improve when practicing intermittent fasting
Laura Frontiero, FNP-BC

Welcome back to another episode of the, “Restore Your Mitochondrial Matrix Summit.” I’m your host, Laura Frontiero, and I’m bringing you experts to help you boost your energy and fix your health so you can build a life you love. And today my special guest is actually a friend of mine and fellow Nurse Practitioner, Cynthia Thurlow. Hi, Cynthia. Welcome to the Summit.



Cynthia Thurlow

Hey, Laura. It’s nice to be with you today.


Laura Frontiero, FNP-BC

Yes, it’s so good. Oh, now you are an intermittent fasting expert and I’m so excited to bring you on here and talk about this. You are the author of the best selling book, “Intermittent Fasting Transformation.” You’re a two-time TEDx speaker, and your second talk has over 10 million views by now. And you’re the host of “Everyday Wellness” podcast, and you’re a globally recognized expert in intermittent fasting, women’s health, and you have a really important mission. Your mission is to educate women on the benefits of intermittent fasting and overall holistic health and wellness so they feel empowered to live their most optimal lives, which is so aligned with what we’re up to on this Summit. And the reason I’m so excited to bring you here is because intermittent fasting is so critical to mitochondrial health. You can’t talk about mitochondria without talking about intermittent fasting. And I know that this is something that you are passionate about. You love this. You pretty much can’t talk about intermittent fasting without talking about mitochondria as well. So we’ll just establish this right now. This is so relevant to the topic. Pretty much everything you’re gonna share with us is gonna support mitochondria. So welcome, and thank you so much.


Cynthia Thurlow

Thanks for having me. As I said, I love talking about the science behind fasting. I think a lot of people wanna focus on the physicality, what are the things you can change about body composition or losing weight? And I would say there’s so much more that goes on behind the scene, and the mitochondria are powerhouses of ourselves so we want to have healthy mitochondria, or at least the healthiest mitochondria, irrespective of where we are in life stage and age.


Laura Frontiero, FNP-BC

Absolutely. So I just wanna jump right in with this topic because I know people even like me, I mean, I kind of came, I was telling you before we started recording that I kind of have not intermittent fasted because I didn’t feel like I could have my coffee without my almond milk and my coconut sugar. And I just, I wasn’t willing to let that go. And finally, at age 49, I’m finally intermittent fasting and it’s not as hard as I thought it would be and I’m going like 16 hours now. And it’s not as hard as I thought it would be. So let’s talk about what the different types of fasting are and start out with why the 16/8 fast is a good starting point. So can you break it down for us?


Cynthia Thurlow

Yeah. Well, first and foremost, I wanna acknowledge that you are officially fasting. And I think for a lot of people, it’s all about mindset. We convince ourselves that something is not possible and then when we reframe things and think about it a little bit differently, we’re oftentimes pleasantly surprised. So when I’m thinking about intermittent fasting, it’s choosing to eat within a specific timeframe. It’s eating less often. And so I think the 16/8 as one example has become very popular because that’s fairly attainable. People can say, “Okay, if I stop eating at 6:00 p.m. “and then I don’t eat again until 8:00 a.m.,” they don’t realize they’re already 14 hours fasted and that’s pretty exciting. 

So going an additional two hours will get you to 16 hours, and that’s usually a good starting point. But obviously as you inferred, there are other types of fasting. There are longer fasts, 24, 36, 48, 72 hour fasts. There are alternate day fasting where you may do a fast, a 24 hour fast, in between regular eating intervals. You can have different types of fasting. There are people that will just do 12 hours of digestive rest. And I think that’s the bare minimum for everyone that really, irrespective of life stage and age, we should all be not eating for 12 hours at a time because it really does fine tune our digestive processes, our endocrine system, our hormones, et cetera. And then I also think about unique circumstances. There are people that eat OMAD, one meal a day. There are people that eat within very short feeding windows. 

That’s generally not what I recommend for most women, however. It’s very hard to get your macros in in that short narrow window. But when we’re talking about a fasted state, there are different types of benefits at roughly specifics types of intervals. So obviously if you are looking for stem cell activation, you’re really looking to boost gut health, you’re gonna fast a little longer than maybe a 16 hour fast. If you’re someone that’s really maybe coming off of an illness, really wanting to boost autophagy, which is this removal of diseased and disordered organelles and mitochondria, you might fast for 24 hours where we know that autophagy really gets up regulated. So there’s a lot of different ways to look at fasting. 

A lot of it’s defined by, what are your goals? And I think that’s important for anyone, irrespective of where they are on this journey, to really define for themselves so that they can then select the appropriate window in which they fast. The other caveat that I would add to that is obviously, women that are still at their peak fertile years or women that are perimenopausal, still getting a menstrual cycle, it’s important to know there are certain times in their menstrual cycles where they should not be fasting. And that’s something that I definitely address and talk about in the book. But important for women to know that until you go through menopause, that women have specific times during the month that they can capitalize on fasting and other times they should back off. But men and postmenopausal women generally have an easier time because there’s less hormonal flux day to day, week to week, month to month.


Laura Frontiero, FNP-BC

Yeah, I think I’m finding it easier as I get older to do this. Okay, so I have a couple questions for you before we jump into metabolic flexibility. But this is just what’s popping up for me right now is this kind of feeling, or this thing that we were taught that breakfast is the most important meal of the day. And even feeling kind of guilty if you don’t eat breakfast because you’re losing that opportunity for the best time of day to eat, which is what we’ve been taught, and the most important time of day. And the second thing I wanna ask about is my daughter. So she is 16 and she naturally does not wanna eat breakfast. I literally have to force her. She doesn’t wanna eat till 10 o’clock in the morning. She’s been that way her whole life. And have I caused any problem by allowing her to go to school without eating? So can we just talk about those two things? ‘Cause I think other people have the same question.


Cynthia Thurlow

Yeah, well, I would say first and foremost, breakfast is the most important meal of the day. If you look at chronobiology or if you look at circadian rhythms, if you wait at least an hour from the time that you wake up until you eat something, that is better than waking up and instantly eating. The people that have taught us that breakfast is the most important meal of the day are the processed food industry and generally what they are peddling and encouraging individuals to consume is a very carbohydrate centric breakfast, which is about the worst thing you could start your day with. So I oftentimes will remind people, we know based on research that most, if not all, people actually do better breaking their fast earlier in the day. So 10, 11 o’clock is completely reasonable. And you always wanna focus on breaking your fast with protein and fat or protein and carbs because protein, protein, protein is probably the most important macronutrient on a lot of different levels. 

Now, the ironic thing is I have two children, both teenagers, and my 14 year old, who’s a competitive swimmer, does not like to eat breakfast at all and has been that way for probably the last three or four years. And he has a very compressed feeding window. He’s not fasting, but he gets up and he wants to have coffee. He’s hilarious. He’s like a 14 year old going on 70. Wants to have his coffee or his espresso, and then a couple hours later he wants to eat. And so, much to the point with your daughter, I think there are those of us who are early risers and wanna eat, there are those of us that wake up and we can put off eating for several hours. And so because our children technically are still growing, even though they’re not fully developed, even as teenagers, not yet, I always remind people that I never discourage people from intrinsically leaning into what feels good for them, but I would also be remiss if I didn’t say, when I talk about a fasted state, I’m really not applying it to those circumstances. 

I’m just saying leaning into where your body is telling you, “It’s time to eat. “It’s time to break your fast.” And I’m sure your daughter, because she’s your daughter, I’m sure that she gets plenty of macros in during the time period in which she eats. And as a teenager, she probably has a metabolism of a hummingbird like mine do. But I think for a lot of other people that are listening, that are concerned, that they’ve been convinced that you eat frequently to stoke your metabolism, breakfast is the most important meal of the day. When we break our fast can be any time during the day. So yes, when you break your fast, that first meal is very, very important to the metabolic flexibility and your metabolism for the rest of the day. So that’s why I always lean into don’t focus on corn flakes, or a bagel or a muffin, that’s dessert. 

I remind people all the time, let’s just call it what it is. It’s dessert and it’s designed to dysregulate your blood sugar, make you hungry and hangry, and you’re gonna be eating more food an hour or two later. So really focusing in. When you choose to break that fast, protein and fat, protein and carbohydrates, are going to be much more readily available to keep your blood sugar stable in between meals. But I do think, and I do find, ’cause I get this question a lot about teenagers that don’t like to eat early in the day. There’re probably kids that stay up later at night. They become bears as teenagers. 

You know “Bears?” Michael Bruce’s book on how each one of us, depending on where we are in life stage. I’m still a lion. I think that’s a byproduct of being in the healthcare industry from years of having to either be in the hospital late at night or early in the morning. And then teenagers are these bears, they eat later, they get up later, that’s just their natural inclination. But I don’t think per se that’s causing harm as much as I think we need to honor and embrace our children as unique individuals. And I would never say to my 14 year old, “I want you to get up at seven o’clock in the morning, “eat a breakfast,” ’cause he would feel miserable. Whereas my 16 year old gets up and has a massive breakfast and then goes to school and that’s his way that he eats. He eats earlier in the day and that works for him.


Laura Frontiero, FNP-BC

Yeah, I think really pointing out how unique everyone is. And my daughter has always intuitively known. She’s really got healthy relationship with food. She eats when she’s hungry, she doesn’t when she’s not, and she doesn’t eat for pleasure. And so that- But she enjoys food. And so it’s been tough as a mom to just embrace allowing her. When she was in elementary school, the teachers actually got mad at her because at 10 o’clock she wanted to eat her lunch at snack and they punished her and said, “No, that’s for your lunch. “You’re not supposed to be eating that right now.” And I said, “You eat whatever you want “during your 10 o’clock break. “If you feel like eating the lunch piece of it “and not the snack piece of it, you go for it.” Right? Because that’s when- Anyway. The other thing I heard you say is, “Breakfast is not defined by a certain time.” So society says breakfast is from 6:00 a.m. to, I don’t know, before lunch. If you’re breaking your fast at noon, that’s breakfast. Break the fast and you make that meal worth it. That’s what I heard you say.


Cynthia Thurlow

Yeah. And I think it’s important for people to know that we can break the rules and the conditioning and the dogma that so many of us grew up with. My mom was Italian and she never wanted me to leave the house without eating breakfast. And I remember I hated it. She would send me to school with a English muffin with butter, which I probably tossed in the trash. But I came to find naturally, I was someone that didn’t wanna get up and eat in the morning. I’ve never been one of those people. And so for me, intermittent fasting was fairly easy for me to do for that reason. But I also think that, and this is contrary to what we learned as nurses and as NPs, there’s no universal prevailing, everyone has to assimilate to everyone eats at seven and then they eat at 12 and then they eat at five. 

We have really destroyed people’s perceptions of what meals should look like, what they should be constituted by. We’ve convinced people on so many levels that they have to lean into what everyone else is doing as opposed to honoring who they are as individuals. And so a lot of the work that I know both of us do is encouraging people to find their own way, experiment. It might be that for you, Laura, you can break your fast at 10:00 a.m. and that’s fine, and maybe your husband does at 1:00 p.m. In fact, that’s kind of what my husband and I do. He breaks his fast later and he actually feels really good. He likes to get through his morning, get all his stuff done, and I’m like, I like to eat earlier and end my fading window earlier and that just works really well.


Laura Frontiero, FNP-BC

Yeah. Yeah, no, I hear you. I’m also really good at one meal a day. I mean, it’s crazy if I don’t- If I eat a nice meal at one, don’t eat until one, and it’s great, I kinda maybe something really light by six o’clock. But anyway. So I think what we’re doing right now is giving you permission to do you, right? Everybody listening, you get permission to do you. There is no wrong way to approach this. So I wanna get into metabolic flexibility and how that improves when you’re practicing intermittent fasting. And this is really critical from a mitochondrial standpoint as well, this whole concept of metabolic flexibility, because when you don’t have metabolic flexibility, you end up in metabolic instability and then you end up on the pathway to chronic health conditions. So share with us about metabolic flexibility.


Cynthia Thurlow

Yeah. My kind of prevailing statement about this is, “Metabolic health is wealth.” And so when people are so fixated on dollars in the bank or investments, I remind them the most important investment they can make is in their metabolic health. So what this looks like is… And this goes back to my Nurse Practitioner brain, so that people have quantification when we’re talking about metabolic syndrome or we’re talking about things that it demonstrate to us that we’re not metabolically healthy. Number one, we look at waist circumference. So if you are a man with 45 inches or greater, woman, 35 inches. And for a lot of people, this is a huge problem. If you have triglycerides that are greater than 150, I like to see them as low as possible sometimes under 75 grams, ’cause this is almost always a reflection of the degree of processed carbohydrates and alcohol someone’s consuming. For men in HGL, you want it greater than 45, women greater than 55. Looking at fasting insulin, this is more often than not looked at enough, but I like to see those numbers between two and five milligrams per deciliter. 

Fasting glucose is also looked at, but I remind people, fasting insulin is more often than not one of the first biomarkers that will dysregulate. I don’t know about you, Laura, but when I graduated my NP program, glucose was under 140. Now we want it under 100 and ideally, 75 to 90 is where I like to see it in a fasted state. So when we talk about metabolic health, those are some parameters. Also blood pressure. So you wanna not be leaning towards being pre-hypertensive, so 130 over 80 or below is ideally kind of where you wanna be. When we’re talking about metabolic flexibility, from a mitochondrial perspective, it’s being able to utilize two different types, or three if you look at ketones as another one. A couple different fuel substrates or alternate options for fuels, whether it’s carbohydrates, fats or ketones, and it’s important for people to understand that the mitochondria in and of themselves are the powerhouses of our cells. What we choose to eat and how we live our lifestyle can have a lot of impact on how well they are properly regulated, managed, dysfunctional, or functional. And one little fast fact, which I’m sure your listeners are probably already aware of. 

After the age of 40, more often than not, we have quite a bit of dysfunctional mitochondria. So add into it if you’re under the age of 40 and you have a chronic health issue, you’ve got insulin resistance or diabetes, you’re well on your way to having a significant degree of mitochondrial dysfunction. But when we talk about meal frequency, as one example, if we are eating snacks and mini meals and eating a conventional standard American diet which is full of hyper-processed, hyper-palatable foods, low on protein, high on adulterated fats like seed oils, low in high-quality carbohydrates, kind of leaning into the processed carbs and you’re eating frequently, what you’re doing is you’re setting your body up for initially some blood sugar dysregulation. So every time you eat, your body in response to protein, fat and carbohydrates creates a certain amount of insulin to bring your blood sugar back down. Now the most negligible macronutrient are fats, but it has to be the right types of fats and not adulterated seed oils. Next is protein and then carbohydrates. 

So I always remind people, that’s why I always suggest protein and fats, protein and carbs, because it’ll have a more negligible impact on your blood sugar. But if you’re constantly eating and you’re constantly secreting insulin, one of the things that will start to happen is in a high insulin state, your body is in fat storage mode so everything that you’re eating just gets packed away as added calories. I always use the example of my father who likes to top off his gas tank. So you’re driving your car, you never give your car, which is your body, the opportunity to burn off the excess fuel and you just keep topping it off every time you eat. So if you’re eating frequently, you are contributing to blood sugar dysregulation. You are contributing to your body only really utilizing that quick source of fuel, if at all, which are the carbohydrates. Which explains why a lot of people inflexible, they get hangry, they get very grumpy when their blood sugar drops, they deal with energy slumps after a meal. If you fall asleep after a meal, that’s a good sign that you have put your macronutrients together in the wrong way. 

More often than not, it’s too many carbohydrates. It means you will struggle to lose weight. I mean, how many of these people that we talk to day to day are dealing with weight loss resistance? And so this is really a starting point, a stepping point, to understanding that our body is designed to utilize both carbohydrates and fats as a fuel source and when we’re not eating as frequently. So Laura mentioned, now you’re fasting one or two meals a day. In between, your body is able to go in and effectively utilize stored fuel as a fuel substrate, usually fats. Our brains love fats, as an example, which is why when people are in a fasted state, they’ll more often not express a lot of mental- They’ll have a lot of mental clarity, they have a lot of energy. Over time, your body will allow you to kind of suppress the hunger response, which is why people can kind of effortlessly fast for longer periods of time. But when we’re in that fasted state, our body, once we become more metabolically flexible, will go in and free up fatty acids as a fuel source. 

And so these fats, and one in particular I like to talk about, beta hydroxybutyrate, which is a ketone, diffuses across the blood brain barrier and gives us all this mental clarity. So we really wanna get to a point where we have burned off all of these stored carbohydrates so that our body can get to the stored fats. And our mitochondria in particular are like little spark plugs, and so they like to utilize, depending on what demands are on your body. If you’re running a sprint, you’re gonna use a different pathway than someone that’s doing an endurance race or has a short sprint. And so it’s really important to understand that our meal frequency is but one of many factors that can impact metabolic flexibility. I also think about things like sleep and stress, I’m happy to go into those, nutritional choices, all of which can impact the quality of the mitochondria. And it goes without saying, because I talk about this so frequently, that if you do nothing else other than try to eat less often, one thing that you can do that can really improve the quality of your mitochondria is to avoid seed oils. 

And what are seed oils? Canola, cotton seed, soybean, sunflower, et cetera. The number one consumed fat in the United States right now is soybean oil because it proliferates in the processed food industry. But what it does to the mitochondria is of relevance to everyone. We know that it damages the cellular membrane. So if it damages the cellular membrane, it’s going to have a net negative impact on those mitochondria. And we know, based on research, it can damage the cellular membrane of our cells for up to two years. So it is not as benign as the processed food industry would really like us to believe. So if you do nothing else to preserve the quality of your mitochondria, you eat less frequently, make different food choices and really try to avoid seed oils. Those couple things alone can do quite a bit for your mitochondrial health.


Laura Frontiero, FNP-BC

I’m so glad you brought this up, Cynthia. And I just wanna go onto a little bit of a soapbox about seed oils for a second, since you brought it up. And a lot of our audience are really busy, high-level performing women who have families and they are ultimately responsible for feeding their family. And so… And it’s just it. That’s just the way it is. I mean, I live in a household where my husband does like to grocery shop and likes to- But I’m still the one who says, “Okay, this is what we’re gonna have for dinner tonight.” It’s just kinda naturally my role. It makes sense. And we think we’re doing a good thing when we go to Whole Foods and we go to Trader Joe’s and we go to Sprouts and we get all these healthy prepared foods, but you really have to be a label reader because most of the time, there’s a seed oil. 

Being olive oil and avocado oil and walnut oil, these are expensive oils and they’re often not used by even in healthy foods. So I implore all of you listening to be a label reader. I can’t tell you how many times I go to Trader Joe’s, I love Trader Joe’s, and I see they’ve got all these healthy salads and prepared things, and I start reading labels and it’s canola oil, sunflower and safflower oil. Those are the things that they tend. And soybean, but more of those first three. And I put it down. Or a hummus that’s laced with canola oil and olive oil. And so, it’s I just have to go there. You gotta put this stuff back on the shelf. I literally have picked things up my taste buds, I’m salivating, I wanna eat it, and I read the label and say, “Nope. “I’m not putting that in my body or my family.”


Cynthia Thurlow

Yeah. And it seems so innocuous and benign, and I affectionately refer to Trader Joe’s as Trader Junk because in the context of, yes, you can get some good prices on fruits and vegetables, but if I go through Trader Joe’s just eliminating seed oils, it’s most, if not everything, that’s in there. And so, I think that people make the presumption that if it’s in the grocery store or Trader Joe’s or Costco or whatever, we really have to be detectives. And in my house, my husband and I kind of share the responsibility of grocery shopping. And he knows that, my kids it drives them crazy, but I always remind them, “It’s a cumulative bucket.” We were talking about buckets before we started recording. It’s a cumulative net exposure. But it’s interesting for me when I look at even documentaries, or if I look at film from the 1960s or 70s, how different people look then versus now. You have to believe that it’s not just a byproduct of maybe people being less physically active. It is really looking at the food frequency, the change in ingredients. 

And if it’s not the seed oils, it’s high fructose corn syrup and fructose in general. And just we have to be proactive about ensuring that we are playing detective everywhere we go. I mean, I’m that person in the restaurant that asks, “What is my steak fried in or cooked in? “What salad dressing? What oils are you using?” And if they say a blend, run. My kids know sometimes I’ll actually bring a little… I’ll make my own dressing and bring it with me and then I don’t have to worry quite as much. But just the realization that unless you’re in a city- Like Austin is a great example of a city in the United States that they seem to have a really proactive system where a lot of the restaurants there, they utilize alternative fats in their cooking. 

And yes, it may impact the cost of the meal, but at least they’re using something better than the adulterated seed oils. And the other thing that I’ll just add and I’ll get off my seed oil soapbox, the research that I’ve looked at and I’ve presented really examined that it’s not just the seed oils. If they’ve been heated over and over and over again, I think about a fast food restaurant, it makes them even more toxic. So even looking at animal models. Seed oils are bad enough as it is, but if they’re being repeatedly heated and reheated over and over again, that makes them even worse. So just something to kinda keep in mind if you’re on that good, better, best continuum that I try to emphasize. Just really being cognizant of where they sneak into your lifestyle.


Laura Frontiero, FNP-BC

Oh yeah. Oh yeah. I’m glad we had this little side note. ‘Cause people ask me all the time, “How important is it really for me to avoid the seed oils?” I say, “Well, in the grand scheme of things, “it’s pretty important. “It’s pretty important.” And so let’s talk a little bit about hormones as they relate to intermittent fasting. So there’s a bunch of hormones like leptin, ghrelin, DHEA, cortisol. What say you about hormones? What would you like our audience to know?


Cynthia Thurlow

Yeah, I would say let’s focus on the big hormones first. And when I think about the hierarchy of hormones, I think about oxytocin, which is so poorly understood, but really a great hormone. I think about cortisol and I think about insulin as being the big players, kind of the bullies on the block that people have these negative connotations of these hormones. And so I remind people that insulin’s a great hormone. I mean, we want to optimize insulin. Unfortunately, we think of a lot of negativity or we think negatively about insulin because we hear people talk about insulin resistance and diabetes and high blood pressure, and PCOS and all these syndromes and disorders that are exacerbated by insulin resistance. So I remind people that we can get a hold of our insulin by changing the food frequency. So how often are we eating? Our food choices. So this means not eating copious amounts of pasta, bread and rice. But if you’re going to eat those foods, have the protein and the non-starchy vegetables first, and then you probably will be able to moderate your choices.

But understanding what impacts insulin most significantly. Insulin is also closely interrelated with cortisol. So I tell people we’ve just come out of probably the last two years, probably the most stressful two years of most of our lives given the global pandemic. And so I remind people when we’re stressed out, that’ll elevate cortisol and that’ll elevate insulin indirectly. So people will say, “I don’t understand why my insulin levels are so high.” And I always have to kind of remind them that there’s this complex interrelationship that stress will do that. Which gets me to intermittent fasting. So intermittent fasting is a beneficial stress in the right amount, at the right time. It’s called hormesis or hormetic stress. And it’s important for people to understand that it’s the right amount of stress at the right time. So if you’re a woman that’s in your peak fertile years and you’re thin, there are times when you should not be fasting. 

And I would probably really emphasize if we wanna get control of cortisol and insulin, understanding that you probably don’t wanna be fasting every day. Same thing for a stressed out mom in her perimenopausal years, the 10 to 15 years preceding menopause. If you’re not sleeping and you’re eating a crap diet and you’re over exercising and your sleep is terrible, don’t add in additional stress. So it goes back to the same thing that if you are fasting in a proper timeframe, so if you are eating less frequently, you’re choosing to break your fast or eat meals focused on protein and healthy fats or protein and carbs, you can absolutely better balance your insulin. We have to also think about cortisol like that stress piece. It’s not five minutes of meditation once a week, it’s understanding that sleep and stress and the type of exercise we do, and the types of foods we choose to consume, we’ve already identified two big players that can impact cortisol in negative ways. Looking at high fructose corn syrup or fructose in general and then also thinking about seed oils can also be impactful. 

Now, the downstream effect and if you think about this hierarchy of hormones, in our bodies, if our bodies perceive that we’re under tremendous stress, it will dysregulate sex hormones. So that means your body preferentially will ensure that you can run away from danger, but it’s not going to preferentially ensure you still have a libido. And this is why I remind people cortisol is also very important for understanding there is a net impact on not only blood sugar regulation, not only sex hormone regulation, but there’s also this complex interrelationship between insulin and testosterone and estrogen and the choices that we’re making. And so remembering the hierarchy of hormones. Remember I said, “Oxytocins first?” Oxytocin can help you lower your cortisol, it can help you balance your sex hormones. But this is the feel good hormone. This is the hormone when we are breastfeeding our babies, or you connect with your significant other, or you’re hugging your pet or something joyful happens, oxytocin will allow you to kind of lower your cortisol. But you need short spurts throughout the day, it’s not a one-and-done kind of thing. 

But I think it’s important for people to understand that if your stress isn’t moderated, that’s going to impact your libido because it’s going to do this downstream effect. It’ll lower DHEA, which will lower your testosterone levels. And the amount of things that we talk about in our environment. I know this is way outside the context of our initial conversation, but when we’re talking about mitochondria, I remind people that endocrine disrupting chemicals can also contribute to mitochondrial dysfunction. It can also contribute to why we have non-beneficial types of estrogens. There are different types of estrogens. Some are beneficial, some are not. This can contribute to insulin resistance. This can contribute to men aromatizing testosterone to estrogen. It can contribute to why women are aromatizing more estrogen in their bodies. And the long story short is that this in and of itself, if we are eating less frequently, managing our stress, dialing in on our sleep, doing the right types of nutrition, we can better manage all of these things. 

Obviously, this is an oversimplification, but it’s really important for people to understand that insulin and cortisol do have a net impact on all of these things. And the other thing to think about is that when we are not sleeping properly, as an example, and we wake up in the morning, we don’t crave broccoli. We crave junk because our body is looking for a quick source of fuel. We know that if you sleep that less than six hours a night, your body is gonna have dysregulated blood sugar, your cortisol’s gonna be up. Cortisol is a hormone that’s gonna have you craving specific types of foods. Again, hyper-palatable, carbohydrate-dense foods, not the broccoli that you probably need, not the steak that you probably need. So it’s important for us to understand that there’s a lot of downstream effect of hormones. That if we are taking care of our bodies, if we are leaning into those lifestyle choices, that not only will we end up with better regulated cortisol, insulin and the downstream of those sex hormones, but we’re gonna be in a position we aren’t gonna have all those cravings, we’re not gonna be dealing with weight loss resistance. 

And I think for far too many people, we’ve been conditioned to believe for such a long time that a pill, a potion or powder is gonna fix everything. And I remind people hormones are such a complicated subject. And obviously, you and I have been doing this for more than 20 years. And I tell people all the time, “I’m always learning new things.” You can’t in a weekend learn all the things because the endocrine system is just so sophisticated. But it really comes back to doing the things for our bodies that are going to lend itself to continuing to improve the quality of our mitochondria, which will give us more energy, which will starve off a lot of chronic health issues that unfortunately, most Americans and most Westernized countries are seeing.


Laura Frontiero, FNP-BC

Absolutely. You’re unpacking a lot here. And so for people who are listening right now, who are thinking, “Wow, this is a lot of information.” It is and Cynthia wrote a book about it, so. And she has some really good TED Talks about it as well. But if you’re feeling overwhelmed by all this information, I’m gonna ask you to just let the overwhelm come down and trust that when you make small little steps and you’re moving in that direction, you are doing good for your body. So on that note, I know that you have some information about fasting for perimenopause, a cycling versus a perimenopause, menopausal woman. Can you give us some quick tips just so- I mean, people might not know when they’re in their follicular phase or their luteal phase, but can you give some, just overview of how do you do this if you’re cycling through your periods? How do you do it if you’re perimenopause and not cycling?


Cynthia Thurlow

Yeah. So the first kind of category I think about is women that are 35 and under. And even if you’re choosing not to have a child, the hierarchy in your body is very focused on food access and your body is very sensitive to food restriction. And it’s not to suggest that most of us don’t benefit from 12 hours of not eating. But if you suddenly go from eating three meals a day, snacks and mini meals, and then you go to eating one meal a day, at that stage of life, your body may do a timeout. So I remind women both in their peak fertile years and perimenopause, that from the day of when you start bleeding until about 14 days in, so we’ll just for ease of explanation, we’re gonna talk about a 28 day cycle. For day one of bleeding to about day 14 before you ovulate, that’s your follicular phase. 

That’s when estrogen predominates, that’s your superpower. I tell everyone this. You can push your workouts, you can do lower carbohydrate, you can do a longer fasting window. Always with the caveat if you’re peak fertile years, you probably should not be fasting every day. That’s your superpower. Then after ovulation, after you have these additional fluctuations in estrogen, testosterone, and also progesterone, you head into the luteal phase. This is when progesterone predominates. This is kind of that mellow hormone. You don’t have the same amount of energy, you may have changes in the foods you gravitate towards, you can’t push your workouts, you don’t wanna be pushing that fasting window. And so I always say the five to seven days preceding your menstrual cycle, that’s the time to back off the gas. 12 hours of digestive rest is fine, but you should not be pushing longer fasts. And then when we talk about perimenopause and menopause, just in kind of that same bucket, this is when, if you don’t take care of yourself, you will hit a wall. And what does this mean? You have to get high-quality sleep, you have to do stress management. This is not three minutes, once a week doing meditation. It means finding ways throughout your day to kind of lower your cortisol, evoke that oxytocin. I’m telling you I have two dogs. I have one dog in particular, I hug him all day long. That gives me a little boost in oxytocin, ’cause I have teenagers and they’re not always as interested in hugging mom. 

But really understanding that this is the time for anti-inflammatory nutrition. This is the time to consider an elimination diet. Maybe it’s gluten and grains no longer serve you. Alcohol is a big issue, huge issue, whole separate conversation on that. And then also finding the right types of exercise. I found in my early 40s, I couldn’t do CrossFit type exercise like I did in my 20s and 30s. I had to find a good balance between strength training and connection with nature, et cetera. For perimenopausal women, the same thing applies. Follicular phase, they can fast. Luteal phase, they have to back off. And then we talk about menopausal women, so women that have gone 12 months without a menstrual cycle. 

This is kind of a cool time. Because guess what? You don’t have as much hormonal flux day to day, week to week. The lifestyle piece still applies, but you can fast more often. You can fast longer depending on how well you’re taking care of yourself. So I always like to remind women that fasting can be an option throughout your lifetime, but it is much more critical in those peak, fertile years that you are not over-fasting. Your menstrual cycle is a barometer. So when young women reach out to me and say, “Oh yeah, I’m 23. I’ve got a BMI of 18. “I fasted and I stopped menstruating.” And I said, “That’s a barometer of your health.” So if you stop getting your menstrual cycle, that is not a good sign. That’s a sign that it’s too much stress for your body. And I think for a lot of women, they’re just so disconnected from their bodies because people have been on synthetic hormones for a long period of time. They don’t even know what their menstrual cycle is, let alone where they are in their menstrual cycle. And so I really encourage women to lean into your physiology and not feel like you have to apologize for it. That’s the really great thing about being a woman is that we aren’t the same day to day, week to week, which I think is a wonderful thing.


Laura Frontiero, FNP-BC

So for men, they can just, it’s not the same?


Cynthia Thurlow

Like menopausal women. Yeah, they have a lot of flexibility. And if you look at the research, and this is always a source of irritation for women, we are not mini men. We have more body fat, we have less muscle mass. Obviously, most of us have a menstrual cycle for 2/3 of our lifetime, and then we no longer have a menstrual cycle. Men, generally speaking, will lose weight faster because they have more lean muscle mass and they have a lot less restriction. But that’s not to suggest the lifestyle piece isn’t important for them as well. But yeah, men have it a whole lot easier in that respect.


Laura Frontiero, FNP-BC

Wow. Yeah. So I’m so glad that you’ve done all this research and work on supporting women, because like you said, we’re not mini men. I love that. We are different.


Cynthia Thurlow



Laura Frontiero, FNP-BC

How might you know that intermittent fasting is not working for you? You started kinda touching on that as you were talking about the different ways to intermittent fast through your cycle. So how would you know?


Cynthia Thurlow

Well, I would say number one, it’s okay if maybe your cycle’s a little lighter, a little heavier, first cycle or two. That should work itself out. But if you became amenorrhoeic, all of a sudden your cycle’s gone, that’s a sign that something is going on and that necessitates a discussion with your healthcare professional. Your sleep is terrible. Like not only should you not fast if you have terrible sleep, you should not continue fasting if your sleep goes south. Meaning if you are a cycling woman or a menopausal woman and you start fasting, and then all of a sudden you’re having hot flashes or you’re waking up in the middle of the night and you can’t fall back to sleep, that’s a sign it’s not working for you. I think the other piece that I would add to that is, if you have a distorted relationship with food. For some people, they may be able to fast, others may not. But I find for some women, they over-fast and then they start binging. 

And so that is also a sign that there’s some- Your amygdala, which is your reptilian brain, is overriding your prefrontal cortex and that’s explaining why you’re suddenly binging ’cause your brain is convinced you’re starving so it’s going to binge. I would say the other thing is if you just don’t have a lot of energy, if you’re really tired, you’re not recovering from your workouts, really leaning into that. I mean, and I do meet women that don’t do well with fasting and it’s okay if that’s who you end up being. And I’ve met men who just don’t do well with fasting. I would encourage people to really be honest with themselves. 

Do you feel better since you started fasting or do you feel worse? I think the other problem that I see for a lot of women in particular is they’ll go to OMAD and they’re chronically under eating protein because they only eat one meal a day. They’ll say, “Well, it isn’t just once in a while “when I go out to a restaurant and I have a big meal, “I’m not hungry for a second meal, “it’s every day, I’m not hungry for a second meal.” And I just remind them, we have a threshold of a certain amount of protein we wanna ensure we’re getting into our bodies every day. That helps support offsetting the concept of sarcopenia, which is it’s muscle loss with aging. It’s not a question of if, but when. It really starts to accelerate after 40. The less muscle mass you have, the less metabolically flexible you will be. You really want to think about your muscles as a glucose reservoir. And we actually become insulin resistant first in our muscles, so that is why it’s so important. We have to hit our protein macros. We have to strength train. We have to get high-quality sleep. 

So the other little dovetail to your question is make sure you’re not over-fasting because I’m starting to see, I always call it fasting rehab. But I’m starting to see women that are over-fasting all the time, and then they wreck their metabolism because their body’s just like, “We’re gonna hold on to everything, “cause we’re not gonna get enough food.” It’s not even a, they go from eating three meals a day and snacks, to just eating one meal and their body initially, they feel good, they’re losing weight. And then all of a sudden, they have to kind of reverse a little bit of what they’re doing to be able to get their protein macros in. 

So that’s the other piece that I’m starting to see. I’m starting to speak more about this because the mindset with a lot of people is that a little bit of fasting is good, then more is better. If a little bit of exercise is good, then more is better. If doing CrossFit one day a week is good, then more is better. And so I hate to keep picking on CrossFit, I’m just talking about intense types of exercise that may not be appropriate for everyone that’s listening. And I think if you kind of work around those things, if you’re looking for those potential issues that may crop up, I think that generally kind of identifies the people that are at most risk for having problems.


Laura Frontiero, FNP-BC

Thank you so much, Cynthia. You have shared so much information. I’m sure people are gonna go back and listen to this interview again and again. As we close, any other tips for maximizing your fasting success? You dropped so many pearls of wisdom throughout this talk.


Cynthia Thurlow

I would say master the clean fast. If you want the best results, you want to clean fast, which means you are not consuming fatty coffees, you’re not using sugar during a fasted state. Because for a lot of people, I would say once you’ve learned the basics of a clean fast, which means bitter coffee. You can actually add things like cinnamon or high-quality salt, if you need to change or buffer the flavor profile, which will not break your fast. You want bitter tea. Bitter is better. Bitter is full of polyphenols, these plant-based compounds that’ll actually boost fat oxidation. And who doesn’t want that? Understanding that keeping yourself well hydrated in electrolytes, clean electrolytes that don’t have any sugars in them, including stevia, during a fasted state. I would say that’s the one thing. Once people can kind of maximize a clean fast, then they generally see the best results. And then you can decide for yourself how you wanna kind of tackle that fasted state. But understanding the basics so that you can then go on and have the best results.


Laura Frontiero, FNP-BC

So good. So how can people find you? Work with you? Learn more from you? Share that ’cause I know everybody is like, “We need more Cynthia!”


Cynthia Thurlow

Aw, thank you. So my website, www.cynthiathurlow.com. I have my “Everyday Wellness” podcast where I get to interview leaders in the health and wellness space. And one of my favorite things to do in my business, that’s where you can see my book, “Intermittent Fasting Transformation,” that’s available on Amazon, Barnes & Noble, Target, or your local bookstore. And I’ve been telling everyone, if you have a local brick and mortar business, please go give them your business. They have really suffered over the last two years. I am active on Instagram. I’m snarky on Twitter. And I do have a free Facebook group called Intermittent Fasting Lifestyle, backslash my name. I have to say that because I’ve had people say, “Oh my gosh, “I’ve got a totally different side of you on Twitter.” And I was like, “Twitter’s the manosphere. “You have to be able to keep up.”


Laura Frontiero, FNP-BC

I love it, your snarky Twitter. And I have the privilege and honor to actually be able to see you personally and spend time with you, and I’m looking forward to it. I’ll see you in a couple weeks. And Cynthia, this has been an absolute pleasure. I just wanna acknowledge you for your work in the field, for how you represent the profession of nursing and being a Nurse Practitioner. You are a stand for this profession and you show what’s possible. You show what’s possible. You are an absolute expert a respected expert in this field, so thank you for shining that light for all of us.


Cynthia Thurlow

Thank you.


Laura Frontiero, FNP-BC

Yes, well, you take good care until next time. Bye.


Related Videos

Mitochondrial Matrix Summit – Day 1_The foundation to building energy and healing your body for good_

The Gut Microbiome & Mitochondria Connection

Laura Frontiero, FNP-BC
Q4 Mitochondrial Matrix Summit – Featured Image – Jonathan Landsman

Avoiding Cancer Cell Growth Naturally

Jonathan Landsman
Q4 Mitochondrial Matrix Summit – Featured Image – Dr. Nirala Jacobi

Gut Health, Vitality Foundation for Fatigue

Nirala Jacobi, ND
Q4 Mitochondrial Matrix Summit – Featured Image – Ken Swartz

Oxidative Stress, Mitochondrial Function, And Carbon 60

Ken Swartz, MS
Q4 Mitochondrial Matrix Summit – Featured Image – Dr. Jessica Peatross

Drainge Pathways, Liver Detoxing And Hormones

Jessica Peatross, MD
Q4 Mitochondrial Matrix Summit – Featured Image – Dr. Nathan Bryan

The Role Of Nitric Oxide In Mitochondrial Function

Nathan S. Bryan, PhD

Single Video Purchase

Intermittent Fasting Transformation

Buy Now - $1.99

Or Access Unlimited Videos from our Library when you subscribe to our Premium membership

Premium Membership

Unlimited Video Access

$19/month    or    $197/year

Go Premium
drtalks logo

SMS number

Login to DrTalks using your phone number

✓ Valid
Didn't receive the SMS code? Resend

Create an Account


Signup with email

Already have an account? Log In

DrTalks comes with great perks that guests to our site don’t have access to. Sign up for FREE


Become a member

DrTalks comes with great perks that guests to our site don’t have access to. Sign up for FREE

"*" indicates required fields


Already have an account? Log In



Login to get access to DrTalks wide selection of expert videos, your summit or video purchases.