Dr. Mike Nelson Flex Diet

Dr. Mike Nelson
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Kelly: [2:15] Dr. Mike, thank you so much for jumping on The Ready State Podcast.

Dr. Mike: [2:19] Yeah. Thank you both so much for having me here. I’m super honored.

Juliet: [2:22] So I want to start, Mike, by asking you, or at least asking you to comment, on the fact that I think you’re basically the most highly educated and certified nutrition person basically on earth. So could you tell us a little bit about who you are from an educational background standpoint, and why you are so into learning?

Kelly: [2:43] And let me just add — I’ll piggyback on that, how did you end up just marrying yourself to this third rail of human exposure of nutrition because it really, it takes a special person to wade in here. Especially when you are so well educated.

Dr. Mike: [3:02] Yeah, so the answer to that part — and I’ll go into the education after that — is I just sort of lucked into it by studying metabolism and was kind of I’d say more of an idiot about it and just the thought that, oh, if we just kind of figure out the science and you explain the science to people, then we’ll solve all the discussions and arguments. And as you guys know, that’s not true at all.

Kelly: [3:24] I appreciate the naivete and hope in that. Like oh, this will be a piece of cake.

Dr. Mike: [3:29] Yeah. You know, some days I do definitely have days where I’m like why did I pick nutrition. Because it’s a very charged topic, even more so now. And I think part of it is because people can choose to exercise or not, but everyone kind of has to eat. So you’re trying to get people to change behaviors and habits of something that they have to do all the time. And then it gets into how do they feel about it. And then this person says that, and this person said this, and everyone’s trying to sell something. And yeah, so I like it. But yeah, I do agree, some days I’m like maybe I should have done more exercise stuff.

Juliet: [4:12] Well, hopefully in this podcast season we’ll try to unpack a little bit of that. That’s honestly our goal. But I’m going to hold you to it. I have to know about your education and motivation.

Dr. Mike: [4:23] Yeah. So I started out like probably most males going to college and like, oh, I’m a 6’3, 156 pound eel-shaped rake looking person. Maybe I should do this lifting weights thing so I don’t end up disappearing down the drain when I shower next time. And I did my undergrad at St. Scholastica in Duluth, Minnesota. Did a bachelor of arts in natural science. And I remember for my phy ed elective, I took a class on weight training. It was the first quarter I was there. And I was all excited. I’m like oh, I’m going to learn exactly all the techniques and everything to do. This is going to be great. I was signed up for anatomy of physiology where we got to work with actual cadavers, which was great. And the coach for the PE class comes in and he takes attendance, and he looks at us and he goes, all right, all you people, you’re going to learn how to lift weights. And some of you, you need to lose some weight. And some of you, and he points at me and goes, holy shit, some of you need to gain weight. I’m like okay. And then he literally disappeared the second day. And I’m like you didn’t teach us anything. It was just check in and free gym, do whatever you want. 

So I, of course, screwed everything up and turned everything into bench press day, and was trying to get the 95 pounds up and eventually got to the 135 where you could put the 45 pound things on the bar and stuff. So, but kept doing more physiology. I just thought it was interesting. But I didn’t know what to do with it. When I was a kid, I used to race these radio controlled cars and would tear everything apart at my parents’ house and not put it back together. They’re like, oh, you should go into engineering. And they have this new thing now called biomedical engineering. But it was so new, like HR departments didn’t know what to do with you. So I ended up doing basically mechanical engineering and looked at more — biomechanics was the area I worked in. But I couldn’t find funding for the project. 

So at the end, I ended up doing a master’s in it and went to the Center for Biomedical Engineering and worked on heat transfer. So they said, hey, we’ve got this new project, it involves heat transfer, but you don’t have any heat transfer classes. So here, go teach yourself heat transfer. You’ve got four weeks over Christmas break. Here’s the book. Have fun. Like oh God, this is horrible, but I guess if I want to graduate, whatever. So I do that and I ended up generating a model used to sit monkeys in front of the large gigahertz transmitter. And about five years after I graduated, my advisor sends me this little thing from the — clipping from the paper that says military declassifies raygun. He goes, yeah, this is your thesis project you worked on. I’m like, oh. He’s like, yeah, it was so classified we didn’t tell you it was classified. I’m like, oh, okay. 

And what it was, was it’s an active denial system. The military has this big transmitter but it’s in the gigahertz range, so very, very high frequency, what’s called millimeter wave. And it only penetrates very, very shallow under the skin. You know, the end of your skin is very sensitive. And what they wanted was something that will light up all of those nerves and make it feel like your skin’s being burnt by a lightbulb. But they wanted to test it and make sure there was no deep tissue heating effects. So that’s what I ended up doing my master’s on. And finished that, decided I’m never going back to school again. That was eight years, that really sucked, but I made it. I worked for a cardiovascular company, actually, for about 10 years, in pacemakers, implantable devices. And realized then that they’re like, hey, if you want to take more college, we’ll pay for it. Great. 

So I started taking more advanced physiology classes. Met a guy and he’s like, well you should just — don’t get a master’s in physiology, just apply to the PhD program in biomedical. So I did that. Eventually got in, which took quite a while. And by the end of it, I had taken five years of classes. I remember sitting in a class for MRIs and the professor is like all right, we are now going to derive all of the equations that are used in our MRI, and he starts scribbling a bunch of math on the board that I didn’t even recognize. And I had a minor in mathematics by this point. Sitting there thinking, going, what am I doing with my life. Like do I really want to be here? Is this really what I want to do? In the meantime, I had been going to exercise physiology conferences for fun, and sit in the back and poke trainers and be like hey, did you see this research study about this cool thing about protein and stuff. And they’re like no. But you guys are trainers, right? You read research, don’t you? They’re like no, we don’t read research. That’s why we come to these conferences. It’s like who the hell are you. So I dropped out and then went over to the exercise physiology department, and that took me seven years to do my PhD in that. And the crazy part is —

Juliet: [9:30] So are you now — I’m sorry to interrupt, but are you 100 years old now? I’m just kidding.

Dr. Mike: [9:35] I’m 45.

Juliet: [9:35] I’m just kidding. I’m kidding.

Dr. Mike: [9:38] Yeah. I started this whole process right when I turned 18. I graduated with my PhD right before I turned 40. So not the recommended course of action. 

Kelly: [9:52] So I want to jump in because you said something that’s really interesting, that turns out even when you were working on the ray gun and you’ve come to measure yourself in lab monkey years in terms of school, you said something about active denial, which is such interesting — the psychology of nutrition and what we tell ourselves around self-soothing. And I think it’s so interesting that you’ve come to be able to speak to the layperson at this very easy to understand, distilled complexity model, after having spent so much time from the other side of the curtain of big medicine, of complex physiology. Do you think that that’s been an asset as you sort of — you know, you aren’t doing what you originally studied, but coming from that school of rigor and that school of complexity and sophistication has to have changed how you thought about this big problem. 

Dr. Mike: [10:54] Oh yeah, definitely. Little phrase I have, which I may have stolen from someone, is that physiology is complex, but your actions are relatively simple. And I think we always want to invert that, right? There’s a bunch of people who don’t want to respect how complex physiology is in just any aspect, and they also want to make all the actions like really complicated too, right? So I think if you can understand the complex physiology, at least the best that you can, especially if you’re working as an educator or a trainer or someone in the field, to me your job is like a glorified translator. It’s like yes, understand the physiology, understand all these nuances as best that you can, or find people who can help translate for you. But then what is the action that comes out of that that the client or the patient or whoever your role is in front of you can actually do? Because they probably don’t need all of the complexity, but they need to know, yeah, eat more protein, let’s start there, right? That’s something that’s actionable, that’s correct that they can do. I think it’s real easy to get kind of lost on both ends of that spectrum.

Juliet: [12:11] Dr. Mike, can you explain to us what the Flex Diet is, and also sort of tie in metabolic flexibility? And before I let you do that, that was actually a phrase I think we first heard from Mark Sisson actually on the last season of our podcast on longevity.

Dr. Mike: [12:24] I listened to that one. Yes.

Juliet: [12:26] Yeah. And I actually had never heard that. And I think at the end, Kelly and I concluded that we were not metabolically flexible and needed to become so.

Kelly: [12:33] Oh, speak for yourself.

Juliet: [12:33] Yeah. But anyway, we actually love that phrase and concept. And anyway, if you could sort of talk about that and the Flex Diet, which I know you invented, and let us know what that all is. 

Dr. Mike: [12:45] Yeah, so the Flex Diet is a system I use with trainers and coaches. And it’s just a combination of metabolic flexibility plus flexible dieting. And how I got into metabolic flexibility was when I transferred to do my PhD in exercise phys, I did it to avoid math. And the first day I sat down in a meeting with my new advisor, advisor walks in and goes hey, we’ve got two new projects and they both involve math. I’m like, uh oh. And he’s like, they’re on heart rate variability and metabolic flexibility. He looks around the table and he points at me and he’s like, hey you, math boy, whatever your name is, these are your projects now. It’s like, oh shit. Plus, it was like 13 years ago.

Juliet: [13:27] This is what happens when you go to school for so long. Everyone just assumes you’re a math guy.

Dr. Mike: [13:33] Yeah. And because I transferred from engineering, they’re like, oh, math, you must know math. So that’s how I go into metabolic flexibility, which in English is, in fitness there’s this debate which is still kind of going on, about what is the best fuel, right? It’s oh, fat’s the best fuel ever, or no, carbohydrates are better, and you need ketones. And it gets kind of confusing. But metabolic flexibility is how well can your body use and handle carbohydrates, how well can your body use and handle fat. It could be dietary fat from what you consume or even just the breakdown of body fat. And then how well can you switch back and forth between both of them depending upon what you’re doing. 

So if you’re just kind of hanging out like we are, having this conversation, probably in your best bet to use fat. You can get a lot more ATP, energy, and you don’t need to get that energy at a really high rate. However, if we throw you on a rower and have you do a 2K or a 500 meter or something pretty hideous that’s horrible, and we’re measuring your performance on that, the ability to use carbohydrates to create ATP, so energy at a faster rate, is going to be in your best interest. Or you go out and you have a dinner that has a high amount of carbohydrates, it’s in your best interest for your body’s metabolism to be able to switch to burning more of those carbohydrates. And once it’s kind of gone through that and keep your blood glucose within a normal range, then you can go back and switch to using fat again. So it’s how do you use both of those fuels depending upon the context, and then how well can you switch back and forth between them. 

Kelly: [15:15] Well, that seems so simple, right? I mean piece of cake.

Dr. Mike: [15:17] Yeah, I know.

Kelly: [15:18] I don’t — what are we talking about? I’m like sign me up. I want to do that.

Juliet: [15:21] Well, first of all, I love that explanation, by the way. I thought that was amazing. But I guess what I would next ask is it is like a light switch in your body where you’re like now I’m going to burn carbs. Turn this carb switch on. Now I’m going to turn fat. Turn the fat switch on, you know.

Kelly: [15:35] And let me follow up with if I’m really good at burning carbohydrate, is it really harder to become more flexible towards fat? And if I’m really good at burning fat, is it harder burning carbohydrate? Is there one way or another? And I know this is a little bit of a leading question, but is there a preference to being on one side or the other?

Dr. Mike: [15:56] Yeah. So the first part is I tell clients it’s more of a dimmer switch and not an on and off switch, right? So imagine like you’ve got a DJ who’s trying to mix the record on the left with the record on the right, which shows you about how old I am too. And you’ve got the little fader switch that goes back and forth, right? So you’re always kind of fading in the left record to the right record, and back and forth. It’s not necessarily an all or nothing, on or off. We’re always running on some blend of carbohydrates and some blend of more fat. And we can change that relative amount by what we’re doing and some different nutritional approaches. 

And to your question, you definitely can get more stuck on one end of the spectrum or the other. I’ve seen some data and testing from pretty high end endurance athletes who are just consuming just tons of carbohydrates, so much so that they don’t even have what’s called a crossover effect. Like they never get below a 50/50 fuel mix no matter what they were doing. I’d argue from a performance standpoint, as long as they can keep those carbohydrates coming in, they don’t run into any gastrointestinal issue or other things that can muck that process up, performance wise they may be okay. I would argue from a health standpoint, they’re probably not doing very good at all. They’re very metabolically inflexible. They’re stuck on that carbohydrate end of the spectrum. 

On the other side, you can have people who are really good at using fat. It’s like we take someone who’s done a ketogenic type diet, so very high fat, lower carbohydrate. And that can be a very beneficial approach. Depends on what you’re trying to do with it. But we know that if we acutely so all of a sudden, we give those people high amounts of carbohydrates, they’re going to have a harder time handling those carbohydrates because their body is really tuned to using fat and to spinning off some ketones. Now if they’re a healthy person, that will change over time, so they’re not definitely stuck there forever. But there’s going to be a little bit of a transition period they’re going to need to go through. So in my opinion, being able to switch from one end of the spectrum to the other end is more of a marker of health and also performance. If you need to get a high-end speed power performance, you can use carbohydrates to do that, and then you can downregulate to go back and use more dietary fat the rest of the time. So you can transition back and forth. 

Juliet: [18:31] So is the Flex Diet sort of a strategy by which someone could become more metabolically flexible?

Dr. Mike: [18:41] Yeah. So what I did then is, so in my head, I’m like okay, so what are kind of the main things you’d want to look at to increase metabolic flexibility within a flexible framework? So I just kind of outlined what are eight different interventions. Everything from dietary protein, carbohydrates, fat, obviously exercise, some aerobic stuff, some NEAT, some non-exercise activity thermogenesis. A fancy word for just moving around and twitching and just general movement in and of itself. And other things like more lifestyle factors such as sleep. 

I know you guys have talked a lot about sleep too. And even just after one night of very poor sleep we can show that metabolic flexibility acutely goes in the wrong direction, right? Insulin changes. Glucose amounts change. Study, I think it was the University of Chicago, took healthy college people, I think they had — they went from eight hours of sleep to four hours of sleep for five nights. And they were basically borderline diabetic by the end of those nights. Now that reversed when they got sleep and they went back. So there’s a bunch of different nutrition and lifestyle factors that can either enhance your metabolic flexibility or potentially can make it worse. 

Kelly: [20:00] So let me jump in and just say that what I’m hearing you say is that when I’m stressed and I drink a bottle of wine and eat cookies and don’t sleep, that that’s not great.

Dr. Mike: [20:09] No because it — and so if we go back to sadly what does a typical American do, right, their glut max looks more like a couch cushion, so they’re not doing any exercise, right? So they’re not doing the thing that makes them better able to handle higher amounts of carbohydrates through various different mechanisms: GLUT4, non insulin mediated uptake, all that kind of fancy stuff. But they tend to have a diet that’s higher in carbohydrates, that’s higher in refined carbohydrates without much micronutrient. So they’re missing out on micronutrients on top of not having a lot of fiber and other things that can buffer how much glucose load they’re going to see acutely. They’re getting kind of whacked from both ends of the spectrum, unfortunately.

Juliet: [20:57] This is a little bit of a turn, but why is nutrition so — and I’m asking you this because of your extreme educational background. But why is nutrition so difficult to study and get good results? You know, I think every time — I think everyone wants to know, you know, what does the research say. Should I be on the Paleo diet, or should I be ketogenic, or should I be this or that. And the research, at least in my universe, always seems to fall kind of short to coming up with an answer to that. And is that just because we’re all different people and different things will work for different people? Or why is it such a challenge? Or do I have that wrong? Is there really good research?

Dr. Mike: [21:40] I would say there is some really good research. Of course, not as much as what I would like to see. Then it goes into funding and all different types of things. If you’re looking at more on the performance side, performance research just generally is not funded as much. But I think the big thing is, both from a research standpoint and for people trying to comprehend it, is a lot of it is more complex than what I would call state dependent. So for example, right, if we look at carbohydrates, right, everyone’s arguing about are carbohydrates good or bad. Well, it depends upon who we’re looking at, right? If we’re looking at giving a huge amount of carbohydrates to the average American who, like Kelly was saying, is very stressed, drinks a bottle of wine at night to try and relax, they don’t get very good sleep, that’s probably not going to show many benefits, right? They’re going to see a lot of stuff going in the wrong direction. 

However, if we take a high level athlete who’s then burning through tons of calories, and we’re looking at performance and maybe even some markers of health, they can handle a lot of carbohydrates. I mean I’ve had some people working to qualify for the CrossFit games and stuff, and we’ve looked at their health parameters, and they’ve been fine, and they’re going through 500 plus grams of carbohydrates a day. So it depends upon the state of the physiology of that particular person, to me, more so than the particular macronutrient. 

And we always want to look and go, whoa, is fat good or bad, what about protein, what about carbohydrates. And the answer depends upon, well, in what context and with who. And that’s the part that makes it I think harder to comprehend. And the amount of studies and research that you would then need for all these kind of different cases and spectrum makes it a lot longer and more arduous process. And then even add in, well, what are you using as a marker of health. Are we just looking at fasting glucose, are we looking at triglycerides, are we looking at performance metrics? What are we kind of trying to say is a marker of health also? And so that adds like a whole other layer of complexity to it. 

Kelly: [23:55] And I want to say that the only marker of health most of us care about is do I look good naked.

Dr. Mike: [24:00] Yes. Yeah.

Kelly: [24:00] Which may or may not be a marker of health. You know, one of the best examples we love of people being metabolically flexible, and we’ve probably used in this podcast, comes from our friend Laird Hamilton, who says look, if we’re working out for a long session and you bonk, you’re a liability. Like that’s not good. And conversely, we go and the only fuel source available to us is a big, juicy hamburger with a big bun, and that freaks you out, that’s also less good. You should be able to use fuel as fuel. So the question is, I love this approach of this metabolic flexibility, and I really appreciate how you have approached this and what you’re doing. Is this an appropriate strategy for health or is this a more appropriate strategy for performance or is it both?

Dr. Mike: [24:49] To me, I think it’s both. Although I will agree that at some point if you’re trying to get to elite levels of performance, it’s probably going to diverge a little bit, right? I mean I don’t know a lot of extreme elite who I’d say are incredibly healthy. You know, at some point, you’re probably going to sacrifice some of that. Although I would say I think too many athletes do that way too soon. 

So to me, I view health and performance trying to go next to each other as far as you possibly can. And then the athlete has to decide risk/reward type thing, which way do you want to go. And the good part about that is then I think they’re also related to each other more than what most people would realize. So if we look at just a VO2 max or aerobic performance, we know that’s a big thing related to longevity, as is muscle mass, lower body strength, grip strength, things of that nature. We have some performance metrics that impact upon health. We have an athlete that is generally regarded as more healthy, odds are they probably have a better output, or at least they’ll have a much better longevity and robustness also. I think they’re a little bit more related. And I think that’s obviously why I’m biased.

But I like the concept of metabolic flexibility because that is a marker for health. We do know that if you become metabolically inflexible, that is one of the markers for Type II diabetes and other pathologies that we can use one thing to look at, and we can then view that as both a marker for performance, potentially body composition, and health. And to me, that’s where most people are looking. Granted, I agree with you a hundred percent that most clients I work with are not that concerned about their health until they lose it. But I view kind of part of my job is keeping an eye on that in the background to make sure that we’re still going okay, even though they may not vocalize that. Because I know that one, I would feel bad if we didn’t know what all that’s going on with that. And two, I know that when that goes away, all of a sudden that becomes their number priority in that too.

Juliet: [27:04] So Dr. Mike, I know you still coach people one on one, which I think is very cool. And you spoke earlier about sort of the eight benchmarks you’re looking at. But in your work with clients, is there something in that group of eight that people are universally struggling with, or is it really across the board, some people are good at sleeping and other people at moving, or is there just, you know, one area of focus for you where you just think universally people are struggling?

Dr. Mike: [27:35] Yeah, that’s a great question. So one of the problems that I struggled with was, okay, we’ve got these eight interventions. Then I want to set up this certification where they focus on the top thing first, right? So progressive disclosure, in the past, I would have just ranked that based on physiology. I would have said, okay, let’s look in the literature, let’s look at what things have the greatest impact on physiology. Boom, that’s our ranking, one for me. But as I started working with more people, I realized in reality that doesn’t always pan out. So we’ve got to take into some psychology or their ability to change. 

So for example, sleep is a great one. So sleep, we can argue super high changes in physiology, especially if they’re not sleeping enough. However, trying to get people just to do basic sleep hygiene stuff, and I’m sure you have both ran into this, it’s not super easy, right? Because at the end of the day, they’re like oh, I’ve got a busy job, my drive, I go to work well, most people. Now people are working from home. But I come back home, I’m doing my training like you told me to, have dinner with the family, hang out with the kids for a couple hours, you know, my spouse and I watch Netflix for one or two hours, and then go to bed. 

I’m like ah, but you’re sleeping like six hours a night. So it kind of comes down to, oh, so you’re telling me not to hang out with my wife and watch two hours of Netflix and go to bed earlier. Kind of, yeah. And that doesn’t go so well, right? So sleep has a very high physiologic impact. But I found that the psychological, the ability to change for a lot of clients was very hard. When I rated them, I created a term I just called coaching leverage, which is the physiology impact, times, the client’s ability to change. So if we go –

Kelly: [29:28] That’s great.

Dr. Mike: [29:28] To the other end of the spectrum and say like sleep. Sleep, man, out of a one to ten scale, probably a nine, maybe even a ten, right? We can argue about it. A client’s ability to change? Like a freaking one. It sucks. It’s horrible. I don’t like having —

Kelly: [29:43] I think that’s optimistic.

Dr. Mike: [29:44] Discussions about sleep. I know it’s important. But I know that this is not going to end well. So overall score? Like a nine. But if we go to the other end and go to like what number one is, which is protein, ah, lots of physiologic impact, we need it for recovery, it helps with satiety, lots of benefits to it. And I tell people who want to look better naked that hey, I want you to go home and eat more of this particular thing. They’re like wait a minute, hold on. I thought you were just going to slash my calories and tell me to eat less. But now you’re telling me you want me to eat more of something. Like yeah, I want you to eat more, but it has to be protein. Here’s what it looks like, that type of thing. It takes a little bit of effort and some time and learning. But you know, physiology impact, maybe a nine. Client’s ability to change, probably a nine, right? So they’re pretty good at doing that with not as much effort. So that went to a higher leverage point then. 

So because the issue I saw with trainers who were well intentioned, is if it gets them new data, they listen to people like you, Kirk Parsley, other people, Dan Pardi, they’re like ah, sleep, man, sleep, this is a magic thing. Look at all these physiology changes with sleep, and get super stoked. And they go to talk to their clients and it’s just a disaster. And then they’re like, oh my God, what am I doing, I just got to talk to them more about it. And they’re just kind of pounding their head against the wall when their client’s eating 40 grams of protein a day. Like no, just maybe start somewhere else. Like kind of rig the system a little bit in your favor and in your client’s favor, get them going, and then once you have a lot more buy in, you’re like hey, we’ve done these six different things, everything’s gone really well, you kind of get to stuff that’s a harder conversation. But you’ve got more rapport, you’ve got more buy in, you’re like, oh man, all this other stuff they had me do worked really well, okay, maybe I’ll go to bed an hour earlier and do something different.

Juliet: [31:36] You know, I have to tell you that Kelly and I started tracking everything on a WOOP, which we’re a huge fan of, earlier this year.

Dr. Mike: [31:42] Oh cool.

Juliet: [31:43] And you know, obviously I know a lot of about sleep and talk about sleep and have read books about it, but for some reason, the biggest piece of information I have gotten out of it is how much more time you need to be laying in bed —

Kelly: [31:58] To actually get eight hours.

Juliet: [31:59] To actually get eight hours, right? And so there would be so many nights where I was like, sweet, I’m in bed by 10 p.m., I’m waking up at 6 a.m. and getting eight hours. And then I would be like six hours and fifty-eight minutes, only to learn that that amount, up to an hour of disturbance in the night is actually totally normal. So man, that was a big revelation for me. And I probably wouldn’t have gotten it if I wasn’t tracking. 

But that leads me right into my next question, which is I know you specialize in heart rate variability, which I think, first of all, for everybody, if you could define what that is and what that means. And how do you think that factors into all this and especially from sort of a nutrition given that this whole thing is about nutrition, sort of how does it factor into that generally?

Dr. Mike: [32:45] Yeah. So because HRV was part of my research back when I started doing it, they had to come into the lab. I mean we had bought some used equipment. I had to custom write a freaking MATLAB program on top of it. The custom equipment we bought used was about $10,000 worth of stuff. And they still had to come in the lab just to get a single heart rate variability measurement. Now you’ve got watches, apps, all sorts of stuff that can get an HRV reading. We can argue later about what’s more accurate and which maybe are useful and not useful. So it’s becoming much more ubiquitous now. 

And HRV, at the end of the day, is just a marker of stress. So it’s specifically a marker of stress on what’s called your autonomic nervous system. Your autonomic nervous system has two main branches. One is the parasympathetic side, which is like the brake pedal on your car. If I push harder on the brake pedal, my car is going to slow down. If I increase something which is called vagal tone, if I increase it but I press harder on that brake, my car is going to slow down. So parasympathetic tone, parasympathetic side, is more your rest and digest. Heart rate’s going to become lower. And then we also have the sympathetic side, which is more the stress side. If I step harder on the gas pedal in my car, I’m going to apply more stress to the engine, but I’m going to get a little bit higher performance out of the car. The car is going to go faster. 

So HRV is a really good way of looking at the status of the autonomic nervous system. We can look at the changes from one of the R waves to the next R wave. So we have the EKG. So the QRS, the big sharp pointy thing, we measure really, really accurately from one of those to the next. And we do — instead of an average we do a variability analysis. They should move just a little bit. So if we’re sitting here at rest not doing anything, our heart rate’s going to kind of oscillate a little bit around an average point. It’s a little bit of oscillations, that’s the heart rate variability, and that’s a proxy measure for the stress that’s on our nervous system. And what I like about it is that with most clients, they’re completely oblivious to the amount of stress that they’re under. In the past, kind of like with sleep, I used to have all these arguments with clients about their stress level. And they’re like no, I’m not that stressed. And I’m like but we know from physiology that as people get more stressed, they’re probably not making the best nutrition decisions ever, right? I tell clients, think back to a time in your life when you were really stressed. Like what was your nutrition like? Most of the time it was pretty atrocious.

Kelly: [35:29] Wine and cookies.

Dr. Mike: [35:29] Yeah, right, because they’re biochemically trying to soothe themselves from their stress level a lot of times and they only really know a biochemical solution most of the time. So by making them aware of it, okay, let’s just do this HRV measurement and let’s just do it for four weeks, and we’ll just kind of look at it and see. And by having them look at a specific measure, they’re like oh, wow, this thing says that I’m actually more stressed. 

And at the same time, I have them report some type of context. So they can use self-reported just sleep, energy, training, things of that nature. And if we go back to the sleep argument, I mean I spend, man, lots of years just arguing about sleep with clients. And I started arguing with them about stress, and then I went, oh, this is kind of stupid. Maybe I should just monitor it and show them the data. So I created a little graph that would be their HRV score and how much time they spent in bed. And they would see that how much time they spent in bed went less, their stress would get super high. And I would literally just send them this little graph and be like, single email, what do you think is going on here. And they looked at it and they go, oh my God, when I don’t sleep much, I get really stressed. You’re like, yes. And this is like the same conversations we’ve had ad nauseum for like two months before. But they would smile and nod their head and then they would go back to sleeping six hours. Without seeing some data, it didn’t register. Nice part is, you can use that data, as long as it’s done in a helpful way, to say oh look, you’ve got seven hours of sleep a night. You may not necessarily feel amazing now, but we can see that your stress is getting a little bit better day to day. Now you get that little bit of improvement that they can see and they’re like oh, okay, oh, yeah, so it is helping, oh, okay, good. 

And same thing with nutrition, right? Like their just overall nutrition, whatever you’re using to equate quality nutrition. There’s different ways to do it. And then I’ll do the same thing and just look at their stress. And then I’ll sometimes even correlate their stress to their intake. Oh wow, looks like you had kind of a bender last night, oh wow, you were super stressed. Did you feel like you were really stressed as you fell into a plot of cheesecake? Oh no, I didn’t realize that at all, right? And then you show them the graph and they start thinking about it, and they’re like oh yeah, you know what, I was pretty stressed. Ah, cool, right? So maybe next time when you get really stressed, I’m not saying stay away from cheesecake, but I’m saying let’s just think about it and maybe we can make some different decisions at that point. But if they’re not aware of it, then you’re just talking yourself into circles around it. Until they become aware of it, then they’re like oh, okay, now, okay, now let’s try to modify something.

Kelly: [38:15] Can you just give me one example of that graph? Just send it to me so I can just give it to my clients?

Dr. Mike: [38:21] Yes.

Kelly: [38:21] And it doesn’t matter because I know they’re not sleeping and I know their heart rate really is wrecked. It’s gotten to the place now for Juliet and I because we feel tissue quality, susceptibility to overuse or strain, and even healing, we know is tied to  nutritional density, nutritional quality, but also very much sleep and stress regulation. And I have a hard time sometimes, people will say my Achilles still keeps hurting. And I’m like well, you know, we can mobilize it and we can improve all these other aspects, but we have to take a look at this environmental load. And now we don’t believe anyone when they say they’re sleeping. We say you have to show us, otherwise it doesn’t count. And finally, we have those solutions. But I really appreciate this approach. 

And I think people use technology to lever behavior change to bring consciences because I think that’s really, really insightful. And you’re clearly one of the first people to start to really integrate sort of this biometric capabilities into self-awareness. And just massive kudos. I don’t think people can appreciate how powerful that is. And what we know is what gets measured gets managed.

Dr. Mike: [39:33] Yeah, and for years it’s almost too simple, right? It baffled me that, oh wow, like 80 percent of the time the solution is as simple as making them aware of it? Oh. Because you think that they’re paying me a lot of money, you think they should know about this. I can clearly see the signs. And we talk about it, and they shake their head and they nod and they agree, but yet they were missing that level of awareness. And then you also have the accountability built into it, right, because they know that you’re going to be looking at this thing. They know that they’re going to be sort of monitored for a period of time. Not that they need to be monitored their whole life. You eventually want to get them away from that kind of stuff. But that’s going to then hold them to doing the action items. And then once they do the action items, they’re like oh wow, I do actually feel different. Oh, I feel better. Oh, look, my HRV is better. Oh wow, that actually does work.

Kelly: [40:30] I love it.

Dr. Mike: [40:31] Like the feeling is believing.

Kelly: [40:32] These things are — these systems are tightly coupled, conjoined and can’t actually be seen without actually sort of viewing the whole. One of the things that I think we’re not doing a great job of in human performance at high levels is protecting young women from overreaching. Used to be called the athletic triad and now we call it relative energy deficiency syndrome where we see young women who stop getting their periods, occult stress fractures, they crash their thyroid. One of the things that we’re starting to appreciate is that men and women do not have the same physiologies. And some of our original research really did come from men, 18 to 22, right, in college. Is this metabolic flexibility style training, are there differences between men and women when we’re considering this?

Dr. Mike: [41:24] In terms of the research, I haven’t seen any research that says there’s a big difference between men and women in terms of metabolic flexibility. There is a big difference in research in terms of how well people will use fat under low to moderate intensity exercise, which is still kind of surprising to a lot of people, right. Because if you open most exercise physiology textbooks, it says hey, low to moderate exercise, oh, your fuel source is fat and then you kind of transition to carbohydrates. But a study I did, a study done by Gadecki, another study done by Helge, showed that the variability in that is about 23 to 90 percent. And in some people, these are just recreationally active men and women, so it was mixed, who just come in, we test them in the lab, we find that some are really good at using fat at low to moderate intensity exercise, and that other people are just not very good at it at all. 

And then if you add on top, you’re correct that with most research that we have is mostly on men, although that’s gradually changing now, which is great. And then I see more women have a severe caloric deficit compared to men, I’d say on average, right? And I talked to my friend Dr. Sue Kleiner about this a couple weeks ago, that I don’t know how female athletes got it stuck in their head that like 1,200 to 1,500 calories is a good amount of calories to be at, is just insane, right? And then like you said, you’re seeing REDS, you’re seeing all sorts of symptoms that fall out from their body literally just not having enough energy to do what it needs to do.

Kelly: [43:11] Especially if you’re growing and competing. 

Dr. Mike: [43:14] Exactly. Especially if you’re a younger female, now you’re growing on top of that. On top of maybe interesting food choices that you make. And I’ve even seen more guys now coming in at just these crazy low calorie amounts. And it wasn’t that they were kind of doing it for a set goal for a super acute period of time. It’s like no, I’ve been doing this for like the last couple of years. It’s like oh wow, that is — that’s not good. 

Juliet: [43:48] So Dr. Mike, if I’m listening to this and I think I need to become more metabolically flexible and/or figure out if I already am or am not, what would be the steps I would take?

Dr. Mike: [44:01] Yeah. The two markers that I kind of use that are I would say field tests, we don’t have any equipment at all. So on the carbohydratey end of the spectrum, kind of similar to what Laird was talking about, I use what I call the Pop-Tart test, right? I’m like what food can I find that has about 80 grams of glucose, is dirt cheap, you can find it almost anywhere? Hell, the frosting doesn’t even melt in the toaster. Although I did find if you leave it in a defective toaster, it will catch fire. It would be two Pop-Tarts, right? So can you eat two Pop-Tarts for breakfast and be okay or are you going to be like passed out on the floor and not feel very good, right? Can you handle about 80 grams of glucose with very little fiber, very little micronutrition, very little anything else, and can you still be okay, right? If we were to put a marker on it, we could look at rise in blood glucose, things of that nature. On the other end of the spectrum —

Kelly: [44:58] Just want to go on record as saying, piece of cake.

Dr. Mike: [45:01] Yes. You could use something else too, which then I get hate mail from people who are so against Pop-Tarts and stuff. I’m like it’s just a test, right? I’m not saying eat Pop-Tarts for breakfast every day. That’s not what I said.

Kelly: [45:11] I love it. 

Dr. Mike: [45:13] So everyone’s mad about something. But on the other end of the spectrum, the use of fat, fasting is probably a pretty good marker for that. There’s a new study that came out that looked at that. We know by fasting, if you’re not consuming anything that has calories, that insulin levels go down lower and lower. As insulin levels go down, that’s like your fuel selector switch, which I stole from Jeff Pollock, that low levels of insulin, of course your body to use more fat as a fuel. So if I have someone who can fast for, you know, 19 hours, 24 hours and feel pretty good, they might feel a little bit hungry but, you know, they’re not super hangry, they’re going to be okay, they’re not angry the whole time, they’re probably pretty good at using fat as a fuel. If they can’t make it more than two hours while they’re awake from one meal to the  next, probably not so good in that end of the spectrum. So if you have both of those covered as just a rough proxy, you’re probably pretty good, I would say. You’re pretty metabolically flexible.

Kelly: [46:15] Those are great examples. And I just want to go on record as saying one time after running out of food on a long endurance paddle, we were running a river in the middle of winter basically, I went for help and I opened the van, and there was a box of Costco Pop-Tarts there, and I didn’t crush two. I think I crushed 20. 

Dr. Mike: [46:34] Oh yeah. Of course.

Juliet: [46:34] He was only 18 though, so, you know.

Kelly: [46:36] And completely okay, just want to go on record in saying at that point in my life. So this is the greatest thing I’ve learned in this nutrition piece, I just want to thank you for your science.

Juliet: [46:46] Yeah, except for you get a little hangry when you’re fasting, so.

Kelly: [46:49] No, I don’t.

Juliet: [46:50] Oh my God. Okay, so —

Kelly: [46:51] You’re crazy.

Juliet: [46:51] But wait, I want to follow up on this because I love the sort of low test, the Pop-Tart test, and fasting, and then were someone to want to get a little more techy about it, what would they then do?

Dr. Mike: [47:03] So in the lab there’s not necessarily a gold standard of metabolic flexibility yet. There’s a bunch of different tests. So what we’re kind of looking at is if we have some in like a metabolic cart, we have this thing where you breathe into a tube, and it’ll tell you with each breath how much fat and how much carbohydrates are you using, right? Indirect calorimetry. And I actually bought one, so I have one here. I can do all sorts of fun tests, which is pretty cool. So with that, if you were to come in the lab and you were completely fasted, and we do some very light exercise, we would expect that it’s going to show you’re using mostly fat. So you’re good on the fat end of the spectrum. 

And then if we give you Pop-Tarts or we give you like a glucose challenge, 80 grams of dextrose, we would expect that that number, what’s called the RER, is going to shift and it’s going to go up. Your body is going to transition to using those carbohydrates. So the machine’s going to tell us, okay, yeah, your metabolism now is running more on carbohydrates because a bunch of it came in. But then it goes back down relatively fast within a couple hours. Goes back down, you’ve used through those carbohydrates. You’ve increased your carbohydrate oxidation, and then you’re back down to using fat again. 

Someone who is not as metabolically flexible, with just that simple test, their RER, or how well they’re using fat at rest or during low exercise, they’re not going to be super heavy on the fat use. They’re going to be a little bit hedged. That dimmer switch is going to be pushed a little bit more towards carbohydrates. They can’t downregulate, as hard, to use fat. And then consequently, if we give them the two Pop-Tarts or a bunch of carbohydrates, their blood glucose may spike super high and it may go higher than what we would expect, and it may hang out there a lot longer. Meaning in one study they compared lean to overweight individuals and we saw this. Then they’ll hang out there for maybe two, three, four, sometimes worse case is five hours, right? It takes them a long time to switch back to using fat after a carbohydrate challenge. 

So if you go up a level, you think about high-level athletics, right? So I always think of how fast can you do a transition, right? People who are really good, say the NFL, whatever sport, are probably pretty good at going from zero to very fast, change in direction, all sorts of different things. They’re really good at transitions. And in essence, metabolic flexibility is how well are you at doing transitions between fat and carbohydrates. You can transition faster? Cool, that means you’re more metabolically healthy and I would say that that’s a good thing. At a sort of metalevel that kind of matches a lot of other principles that we’ve associated with physiology too. 

Kelly: [50:02] That’s really brilliant. And I’m just going to say because I’m going to ruminate if I don’t say it, we often do a fast once a month. Juliet loves to go 36 hours. But 24 hours I say, you know what, I’m going to eat. But I’m not cranky. I’m just hungry. But I also weigh 235. And Juliet does not weigh 235. I’m like have you seen my butt, which does not look like a couch cushion.

Juliet: [50:25] I also will tell you, Dr. Mike, that I haven’t always been successful. And one time I broke my fast by eating an entire bag of popcorn, which I don’t recommend because it then caused me endless amounts of digestive problems.

Dr. Mike: [50:40] Oh yes.

Juliet: [50:41] So I’m generally very good at fasting and don’t have a lot of issues. But there’s been some low moments.

Dr. Mike: [50:48] Yeah. I used to not be good at fasting. I was the real skinny guy and I read a lot of John Berardi’s early stuff, and I’m like, oh man, I just need to eat a lot. So I set a watch and I would eat every two and a half hours for literally like three years to get up to a whole 185. And then kept doing that for a while. Eventually, the highest I ever got up to was like 245. But then over doing that for literally like a decade, when I went to go on a trip to Europe where food wasn’t as plentiful because I was a poor bastard and didn’t have any money. Man, you did not want to be around me because I was very cranky the entire time. And doing the research on it, I’m like oh, oh, maybe this isn’t the best thing. Maybe I need to change. Yes.

Kelly: [51:35] That brings up a couple ideas. It’s interesting that NOLS, the original NOLS cookbook, when they were talking about backpacking for long periods of time, they would actually program in days of fasting as a way of just conserving weight in the backpacks.

Dr. Mike: [51:50] Oh sure, yeah, that makes total sense.

Kelly: [51:52] I think it’s really interesting. And also something that you address, which we don’t often hear, I think most of the time when we’re talking about eating, it’s always about losing weight. And what I’ve heard you kind of several times reference is gaining weight is very difficult. And also, if I am not metabolically flexible, that could be a component to not being able to gain weight? Is that also you think fair?

Dr. Mike: [52:18] I think possible. Yeah, there are definitely people that have a harder time gaining weight and I was definitely one of them for a while. I think about metabolic flexibility as also hedging my bets towards health a little bit also, right? So we could eat a lot of crazy food, we could argue about “is that really a good food or a bad food”, but I’m more interested in what is the physiological response to that person. So if I have an athlete who needs to gain some legitimate weight, okay, we’ll figure out a way of meeting the objective. But like I said before, in the background, I’m still thinking about health. So I may have them do just a simple HRV and an AM blood glucose, right, because at some point, if we push too hard, then their health, they’re going to start losing metabolic flexibility and their health is going to start to go a little bit awry. So we’re trying to kind of walk that tightrope a little bit. 

And you see this in some athletes who — take Strongman, you know. We were talking earlier before the podcast about the work Stan Efferding has done with some of those guys and just seeing how these large, massive human beings, different states in their career they’ve had also different states of health also. So I think keeping that in mind in my lens how I view that, is if I can keep them metabolically flexible, if we do have to let’s say do a short period of cutting calories, if they are able to switch faster to using fat as a fuel, I’ll have some athletes just go right into doing, okay, your new setup is on Monday you’re going to do a 19 to 24 hour fast. And if they still have that ability to downregulate and use fat pretty well, they’re going to be able to do the fast and it’s going to be relatively easy for them. 

If we have another athlete who doesn’t have that capacity or has lost it, oh man, that’s going to be pretty hard for them to do that, maybe it takes us another six to eight weeks to get back, we have to take a different method. So yeah, at the end of the day, calories absolutely do matter. No one’s violating the laws of physics or anything. But I like to still keep that capacity because it gives me more options of what to do if we need to change within a short period of time.

Kelly: [54:40] Love that.

Juliet: [54:41] Love it.

Kelly: [54:42] That’s — I mean can this be called not flexibility but like supple, I mean because —

Dr. Mike: [54:48] Yeah. That’s a good term. Yeah. We could write a book about it. 

Kelly: [54:54] Mike, where do we — you have been very prolific. People are hearing this, they’re interested in this, where would they find more about you and how you’re thinking about untangling this Gordian knot?

Dr. Mike: [55:10] Yeah. So best place is just probably flexdiet.com. F-l-e-x-d-i-e-t.com. So obviously, that’ll take them to a certification. Most of the stuff I do now is through the newsletter. There will be a way there to get onto the newsletter, either join the waitlist or a little thing on the top there. And then they can just, once they get the welcome notice, just send me a reply and I’ll send them a cool bonus also for listening to the podcast. And then my other main site is just miketnelson.com. There will be a way to get on the newsletter there also and they can same thing, just drop me a note and say, hey, just listen to this podcast and we’ll send them a cool bonus also. 

Juliet: [55:48] Well, thank you so much, Dr. Mike, it’s such a pleasure to talk to you.

Dr. Mike: [55:51] Yeah. Thank you guys both for having me on here. I really appreciate it and appreciate all the work you guys have done throughout the years. And totally stoked to be here. Thank you so much. 

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