Metabolic health for the endurance athlete - with Dr Philip Prins

This week on the podcast Mikki speaks to Dr Philip Prins about the effect of low-carbohydrate diets versus higher-carbohydrate diets on athletic performance, why endurance athletes still need to care about their metabolic health, why there might be a bias against low-carb diets in academic research, and the implications of his research on us middle aged endurance athletes.

Dr. Philip Prins is an Associate Professor of Exercise Science. Dr. Prince earned a B.S. in Kinesiology as well as an M.S. in Exercise Science from Georgia Southern University, and a Ph.D. in Exercise Physiology from the University of Pittsburgh. His research focuses on, among other things, the practical impact of lifestyle on metabolism and how metabolism impacts health, disease and performance outcomes. Among his many areas of expertise are nutritional ketosis, metabolic responses to exercise, and sports nutrition.

Dr Prins can be found here: https://www.gcc.edu/Home/Academics/Faculty-Directory/Faculty-Detail/philip-prins 

Dr Prins Researchgate: https://www.researchgate.net/profile/Philip-Prins

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Creators & Guests

Host

Mikki Williden

What is Mikkipedia?

Mikkipedia is an exploration in all things health, well being, fitness, food and nutrition. I sit down with scientists, doctors, professors, practitioners and people who have a wealth of experience and have a conversation that takes a deep dive into their area of expertise. I love translating science into a language that people understand, so while some of the conversations will be pretty in-depth, you will come away with some practical tips that can be instigated into your everyday life. I hope you enjoy the show!

00:03
Welcome, hi, I'm Mikki and this is Mikkipedia, where I sit down and chat to doctors, professors, athletes, practitioners, and experts in their fields related to health, nutrition, fitness, and wellbeing, and I'm delighted that you're here.

00:24
Hey everyone, it's Mikki here, you're listening to Mikkipedia and this week on the podcast I speak to Dr Philip Prins about the effect of a low carbohydrate diet versus a high carbohydrate diet on athletic performance, specifically in middle aged endurance athletes which I think a number of us can relate to. And we discuss as a result of his research why endurance athletes still need to care about their metabolic health.

00:53
We also talk about why there might be a bias against low carb diets in academic research and the implications of what his research and what we know about the science has for athletes like us. Dr. Philip Prinz is an associate professor of exercise science and earned a bachelor of science in kinesiology as well as a master of science in exercise science from Georgia Southern University.

01:22
and a PhD in exercise physiology from the University of Pittsburgh. His research focuses on, among other things, the practical impact of lifestyle on metabolism and how metabolism affects health, disease, and performance outcomes. Among his many areas of expertise are nutritional ketosis, metabolic responses to exercise, and sports nutrition. And I've spoken to a couple of

01:49
Dr. Prins colleagues already on the show including Dr. Andrew Kutnick around carbohydrate and health and performance. And I think that Dr. Philip Prins's research really brings another element to the low carb space, because he shares data that in real time shows the potentially detrimental impact of a high carb approach for athletes. So I think you're really going to love listening to what he has to say.

02:19
Before we crack on into the podcast though, I'd just like to remind you that the best way to support the podcast is to hit the subscribe button on your favourite podcast listening platform. That increases the visibility of the podcast out there and amongst the literally thousands of other podcasts, so more people get the opportunity to learn from the guests that I have on the show like Dr Philip Prins. Now I've popped a link to Dr Prins University

02:48
faculty page and his research gate so you can check out his research projects and publications. For now though, please enjoy the conversation that I have with Dr Philip Prins.

03:04
Phillip, thank you so much for taking the time to chat to me today. And as I was saying, I really, I love looking at research around low carb and the emerging research. And of course, from a metabolic health perspective, it's pretty clear that this is a very good alternative for anyone who is sort of wanting to optimize, particularly as we age, that area of health. But, you know, there's also obvious interest with the athletic population

03:34
Though we're cautioned against it because of the performance element. So there is a little bit of this sort of, I don't know, butting of heads, or at least it seems to in that athletic space. What do you reckon? No, definitely. And thanks for having me on. It's definitely one of those subjects or topics that's still a little bit controversial, so to speak. I mean, the dogmatic view, obviously, within the field of exercise science and sports nutrition.

04:02
is that carbohydrates are essential in the preferred fuel source. We can talk about why that is, but that's really been the dogmatic view for the last at least half a century. It really hasn't been up until more recent that obviously there's been more interest in low carbohydrate diets, ketogenic diets, research into them. Obviously, there's been a ton of research, especially over the last 20 years.

04:29
Looking at the more clinical effects of ketogenic diets and low-carb diets, obesity, weight loss, diabetes, cardiovascular health, cardiometabolic risk factors, yada, yada, yada. But not a ton specifically looking at human performance. That's most of my research focus is looking at the effect of low-carbohydrate diets and its impacts on human performance. Also metabolism and cardiometabolic health. Yeah, for sure.

05:00
there's this long standing dogmatic view, right? And I understand that because I went to school and I got my bachelor's in exercise science, I minored in nutrition and same thing for my master's and then also for my PhD, right? So I completely understand that. And a lot of times individuals such as myself are kind of a little bit more on the fringe, right? So studying...

05:28
of studying the fringes and what's going on there, but that's obviously very necessary. We've had a lot of research looking at the effects of high carbohydrate diets and performance, and that's fantastic, but we need some more research looking at the other side. And if low carb diets actually do impair performance, which is obviously the conventional thinking. Yeah, and it's interesting as well when we think about an athlete, like, it's not like every athlete is the same. You know, you've got different sports, you've got different ages, you've got different

05:57
outside influences on the athlete. And of course, you've got different levels of athlete that you've got your elite right down to your novice. So to sort of group everyone in this is not the only way. And then of course, people don't think like that. Like we're very, you know, people are much more nuanced with regards to their recommendations. But I think just to blanket suggests that it's off the table for people, I think seems a little short sighted.

06:26
No, exactly. For athletes, if you're an athlete, it doesn't matter what caliber. High school, collegiate university, obviously professional. The point I'm trying to make is not just professional athletes or elite athletes that are obviously very interested in their performance. It's all the other groups and as you described as well.

06:52
A lot of our studies have looked at recreational athletes. I can tell you right now, those guys 100%, they care very much, very deeply about their performance, whether it's running, cycling, swimming, they participate in triathlons, et cetera. They're very, very serious about their performance. The point being is that obviously the conventional viewpoint has been that if you want to optimize

07:21
you have to consume a high carbohydrate diet. Which implies that obviously if you do the opposite, that's going to impair your performance and no athlete wants to, it doesn't matter what level you are, no athlete wants to impair your performance. So therefore, obviously the vast majority of athletes over the last couple of decades, they follow basically one dietary approach. What our research has basically unfolded or uncovered is we're saying there might be a...

07:51
Maybe there should be more to the dietary prescription for athletes on an exclusively high carbohydrate diet. Yeah. And, you know, Philip, one of the papers I looked at was related to that crossover point, which is essentially the thing which determines fuel substrate use in athletes, right? And you often hear that, you know, at that low intensity.

08:15
we are going to be burning predominantly fat. But as soon as we get serious and want to lift that intensity up, that fat is no longer an option. We have to start burning sort of glucose. But your paper sort of highlighted that that's not necessarily the case. So can we sort of like talk about that to start off with and that crossover point with fuel substrate use and what you guys have found? What you looked at, what you found?

08:44
Yeah. So excellent point. So if you were to look, as I was just alluding to over the last 50 years, so why does the field of sports nutrition have this very high carbohydrate mentality? A lot of that has to do with muscle glycogen, this glycogen-centric view of exercise performance. That's its own separate story. And then a lot of it has to do with this historical

09:13
unable to support higher intensity exercise. Actually, if you go back, you can find the first notion of that was a paper published by Krogh and Lundhardt in 1920. It's a 100-year belief that fat is an inferior metabolic fuel unable to support higher intensity exercise. Now, that wasn't picked up by very famous exercise physiologist, George Brooks. I think it was...

09:40
Brooks and Mercier in 1985. If you have an exercise science or kinesiology textbook, you'll see this figure in there illustrating this crossover concept. Like you were saying, it's basically in simple terms, it's just illustrating this relationship between the exercise intensity and substrate metabolism, obviously particularly carbohydrate and fat metabolism. What it's saying is that...

10:08
As the intensity is increasing, so as you go from low to moderate to high intensity, as the percentage of your VO2 max increases, your rate of fat oxidation goes down and your rate of carbohydrate oxidation goes up, which is just a fancy way of saying that the rate of the percent energy coming from fat is going down, the percent energy coming from carbohydrate is going up. If you look at those papers, so that...

10:35
traditional crossover concept, you say, well, where's the crossover point? You'll see, well, for most athletes, it looks like it's occurring at about 55, 60% of their VO2 max. So what that means at that intensity, which is moderate intensity, right? If you're exercising at 60, yeah, 60% of your VO2 max, 55, something like that. I mean, that's moderate intensity. So it's saying at that intensity, that's the crossover point, meaning that represents an equal split like 50-50.

11:03
between carbohydrate and fat metabolism. But then also it means once you go above that intensity, so once you go above say 60% of your VO2 max, the rate of fat oxidation just plummets, right? So you see this precipitous decrease in fat oxidation. At the same time, you see this precipitous increase in carbohydrate oxidation. So we therefore say that that exercise, especially high intensity exercise, is carbohydrate dependent. We're saying it's dependent upon high rates.

11:31
Not a fat oxidation, but we say it's dependent upon high rates of carbohydrate oxidation. Because if you look at those high intensities, so if you now go up to 70%, 80%, 90%, you look, well, according to this graph, how much energy is actually coming from fat? Well, according to those illustrations, it's almost 0%. So if you're performing high intensity exercise, according to the crossover concept, almost 0% or very little energy is coming from fat oxidation.

12:01
It's almost exclusively carbohydrate oxidation. That's the gist of the crossover concept. Then there's some other things that goes along with it because what the crossover concept is saying, hey, your peak rate of fat oxidation is occurring at this moderate intensity. It cannot increase any further if you go higher above that to meet the metabolic demands associated with exercise. Again, it's such an important point.

12:30
because this whole crossover point, because it warrants further scrutiny, it warrants further investigation, which is what we did, because that line of teaching and reasoning is commonly used as justification to teach people away from low-carb diets. Especially for athletes who are performing more higher intensity exercise, or basically for any exercise that's about that crossover point. Right? So if you're an athlete and you train.

12:58
or compete at basically 60% or higher of your VO2 max. Well, if you understand the crossover concept, then you go, well, my performance is dependent upon high rates of carbohydrate oxidation, not fat oxidation. So therefore, high carb diets, not low carb diets. So, Philips, because it is interesting, right? So I've got a friend, Dr. Dan Plews, and he's done a number of studies sort of looking at ketogenic diets

13:27
in athletes that do that higher intensity exercise. And in his studies, and not just him, because it sounds like, oh, you know, because he's pro low carb, so, you know, it isn't just him that's seen this. But there are multiple studies now that show that performance isn't necessarily impaired by a low carb diet. So this essentially is sort of suggesting that

13:54
reliance on carbohydrate, the way that the crossover point would dictate, doesn't really hold the way that we thought it did. Yeah, exactly. So again, that was what I was describing, right, is this traditional view. But it seems that that metabolic effect is basically just an artifact of the habitual diet that's being consumed by the athlete days or prior to that. And I think that was never understood. Or the impact that diet.

14:23
The impact that the habitual diet and nutrition had on that metabolic response and the crossover effect, I mean, wasn't I think totally understood until more recently, right? Because when, I mean, so the paper that you cited that was published on it and people can go look that up if they want, you know, we kind of reevaluate this crossover concept and

14:51
based on our data, but also from others, like for example, Jeff Volek at Ohio State University, we see this crossover point shifting. It's shifting off to the right for individuals who are habituated to a low carbohydrate diet. You'll see in our study, the crossover point wasn't occurring at 60 or say 55% VO2 max.

15:17
But once these athletes were habituated to a low-carb diet, it was occurring at actually at 85% of their VO2 max. So that was really interesting to see this kind of rightward shift in that crossover point. Meaning when we tested them, which was basically six weeks into the diet or almost six weeks into the diet, at 85% of their VO2 max, which is high intensity.

15:46
That's where the crossover point happened. So again, that's a 50-50 split, equal contribution between carbohydrate and fat metabolism. Before that, it was all fat. So if you go look at the graph, if you even look at that graph, you'll see, oh, well, the majority of the energy was coming from fat before that. And then only at that intensity now, it's a 50-50 split. Only once you go above that, then fat oxidation was going down and carbohydrate oxidation was going up, which is really interesting because

16:15
We then also looked at that crossover graph or illustration. But for when these same subjects were on the high carbohydrate diet, because you might go, OK, well, at 85% of their VO2 max at this high intensity, that's where the crossover point occurred when they were on the low carb diet. So

16:40
Same intensity on the high-carb diet, what was going on? Same intensity on the high-carb diet, 90% of the energy was coming from carbohydrate, only 10% came from fat. So completely different metabolic response. Yeah, yeah. And then what are the implications of this then, Philip? So yeah, because I guess I asked that because it, I mean, that sort of, not only does it challenge the conventional sort of view of fuel substrate use,

17:10
Obviously this has implications for metabolic health too. Sure. I mean, yeah, so you can think of a couple of different implications, but what we have shown is performance, and we can talk if you want more deeper about some of those studies, because it's not just one study, it's a couple of studies now where we've shown, and your colleague like Plews showed the same thing, where performance is not impaired, right, on the...

17:38
on the low carb diet. So we've done performance trials looking at VO2 max testing, so maximal endurance exercise performance, five kilometer time trials, so kind of more submaximal endurance exercise performance or kind of more indicative of high intensity, short duration endurance exercise performance. We've looked at one mile time trial and we've looked at basically repeated sprint performance or like a HIIT workout or interval session workouts as well.

18:08
And in none of these activities was performance impaired on the low carb diet. It was always the same. And so obviously, that's a huge implication because again, that provides athletes with a choice. Right? That means you can experiment, right? As you were saying, I think earlier, each person is basically their own N of one experiment. So, because that's what you see in the studies too, right?

18:38
Because I have the individual data. So you'll see, oh, this person did better on the high carb diet. Oh, this person did better on the low carb diet. But at the end of the day, when you look at the paper and you read these papers, you see the means. And you're comparing the means and is there a statistical significant difference? And in none of these papers there were. So meaning there's at least that starting to present athletes with a choice. Hey, I...

19:04
Here's the conventional view, but what happens when I do the unconventional, now that I know that there's obviously a chance or probability or there's evidence out there that my performance will not be impaired. The other big thing is what we have shown is record high rates of fat oxidation. Yes, I saw that in one of the other papers that we're going to discuss. Yeah. So it seems that, especially athletes.

19:30
They're on a low carb diet, they train. We see the rates of fat oxidation go up quite a lot. Because usually if you look at papers where athletes are on their traditional high carb diet and you test their peak rate of fat oxidation, for a lot of these guys who are athletes, it's like 0.5, 0.6 grams per minute. They go on a low carb diet and it doubles. Yes.

19:59
doubles, or in some cases, even more than doubles. One study we did, it was about 1.3 grams per minute. The other study was about 1.5, 1.6 grams per minute. The one study I was referencing, the rates of fat oxidation were about 2 grams per minute, which is the highest ever recorded, or at least in the scientific literature. It's like, well, holy moly.

20:28
If that's your rate of fat oxidation, and that's interesting because that was measured at high intensity. Yeah. So that's obviously unheard of. So if that's your rate of fat oxidation, you can think about what does it mean from an energy standpoint? Because all you have to do is you just multiply it by nine, right? So to see what is the Kcal worth coming from that. So everybody's taking a nutrition class for carbohydrate and...

20:56
and protein, you get 4k kals per gram. Obviously for fat, it's 9k kals per gram. So if you're saying, well, if you're an aphid and you're training and you're on a low carb diet, maybe you get up to two grams per minute, maybe even more, I don't know. And so then you just multiply that by nine to see, well, what's the caloric expenditure per minute or not just per minute, but by hour. So if we're saying two grams per minute,

21:24
Well, that's 120 grams per hour. Multiply that by 9. That's just over 1,000 Kcal expenditure for 60 minutes. And so that's kind of a main or big, if you're looking for practical application, to sow what. I think one of our colleagues, Professor Tim Noakes,

21:48
I heard him speak about this. It's not in the paper. He did this calculation where he calculated. So Ilyub Kupchogui from Kenya, the guy who runs incredibly fast and who breaks the two-hour marathon, he was able to do a calculation. So for him, let's say he did go low carb, which he is not, but let's say he did go low carb, and he achieves this very high rate of fat oxidation. That fat oxidation based on Kupchogui's body weight, his pace.

22:15
and the energy requirement for the 26.2 miles, that rate of fat oxidation is sufficient to fuel him for that performance. So that's, I think, a big so what that comes from this fat oxidation and what does it matter? And then sure, we can talk later also about, like you were saying, what about the health implications of that dietary choice as well?

22:45
So the practical application then of this example is that if you are able to derive 120 grams of, or the energy from 120 grams of fat an hour because you're low carb. So if you're in an endurance event like a triathlon, for example, where you have these high fuel requirements over an extended period of time, you have to rely less on exogenous fuel because you're able to utilise your own fuel. Is that correct?

23:15
Yeah, there you go. I mean, that's perfectly set. So you've just become less dependent on the exogenous administration of carbohydrate. Now we're not saying, I'm not saying that, yeah, well, so if you're doing those very long duration events that fueling is unnecessary, right? That's obviously fueling is necessary. But now the next question becomes, well, how much? Yes. Because if you look at the traditional approach...

23:43
So anybody familiar with the ACSM or any other sports governing body, their fuel strategies during the race in terms of carbohydrate, it's a lot. And a lot of people also don't tolerate that well, a lot of GI problems associated with that. It's like in some cases, some of the recommendations, 60 grams per hour or sometimes more than 100 grams per hour. If you look at some of these studies, you go, wow, that's a lot.

24:12
I think, especially in a low-carb state, you can probably get away with much less. Actually, I don't want to get into too much of the details, but we're about to start another study looking a little bit more at this concept because we're looking at the amount of carbohydrate consumed.

24:39
during exercise, especially when you're in that low carb state and fat adapted, but also looking at this concept of bonking and this whole hitting the wall phenomenon. People say, well, that's to do with glycogen depletion. Well, another counterpoint is that it has to do with hypoglycemia.

25:08
just a small amount of carbohydrate, especially in that fat adapted state, to prevent the hypoglycemia. So, that's kind of what we're going after and where the research is going next. Yeah. Well, that's interesting because of course, you're right. When I look at the literature and I'm just talking to clients and myself, gut issues are a real problem.

25:34
And it's often that's the thing that takes you out of a run, you know, an ultra run or a triathlon. It's not the fact that you haven't done the training, it's that your stomach can't sort of, you get this sort of GI issue. And Philip, I don't know, like when I look at the literature, if I just go back to the high intensity sort of training studies, like I feel like the attention is always turned towards the research group that looks at the racewalkers and you know, and their suppos...

26:03
the findings from the Racewalker studies that clearly this shows that a low-carb approach is not appropriate in this setting. Whereas these other studies like your research, the research of Minton about the Plues and also Paul Lawson has done research in this space as well. It's almost like these studies are not really talked about or they don't have the same fanfare, I suppose, as the other research studies.

26:30
Yeah, you're correct. You hear a lot about the Luise Burks from Australia, the famous racewalking study. Well, a lot of the data they have published has been on the racewalkers. They're Olympic racewalkers. They've shown in most of their studies, I don't think I've ever seen a positive finding coming from that group.

26:59
That's not meant to be a derogatory statement or being negative at all. I'm just saying, usually the low carb diet is doing something negative in those athletes. We haven't found that. Obviously, there's differences in study designs. The difference in study designs is probably explaining some of the differences. Other people might say, well, it's...

27:27
Maybe it's because they're elite athletes. I mean, I don't know. It's very hard to study elite athletes. So I mean, kudos for her for doing that. But I don't agree with and I don't understand a three week adaptation period that they've used in their trials. Not quite long enough. So that's, yeah, I mean, I don't think so. A lot of other people in this space would also don't.

27:54
I don't think so. It's shorter than the four weeks or more that it's been shown to be more optimal. The other thing is a lot of these studies are not either randomized and they're not controlling for some other confounding variables. We, therefore, think our studies have maybe a little bit more weight to carry because we're...

28:24
The diets are usually isocaloric, we're controlling for body composition and also training. When you're doing that, that means the effects that you're seeing in your study should be diet-induced. Because that's what you're going after in these dietary interventional studies. You're looking for diet-induced effects, but if you're not controlling for these other things then it could be something else.

28:52
Yeah. And I mean, I guess at the end of the day, if you're a race walker, maybe this might not be the diet for you, but for the rest of us, maybe there are alternatives out there. And Philip, I would say one more thing with that. I know Tim has talked about that. So Professor Tim knows. He looked at that study very carefully and he's been pointed out many

29:22
his discussion on that, because once he took a deeper dive into it, I think he found many issues associated with that study. Yeah. Okay. That's great intel. Thanks, Philip. I'm really interested in your studies looking at the middle-aged cohort, which can I first say is 39 really middle-aged? Surely these are just young men still, surely.

29:50
But anyway, because most of us actually fit into this age bracket now where we are the athlete that we're not elite, but we're very serious about our sport and we take it seriously. And you looked at these highly trained middle-aged athletes, which were either habituated to LCHF, so lower than 50 grams of carbohydrate a day, or high carb, low fat. So

30:17
Why did you choose that cohort to look at first and foremost? Yeah. So that cohort was a little bit older than our previous cohort. And so part of the reason had to do with that study wasn't just looking at performance, but it also was looking at end-share performance, metabolism, and also cardio metabolic health. And so you'll see if you read that study. It's not just, well, here's the performance stuff, but here's some health-related stuff as well.

30:47
And so we thought it would be interesting to maybe look at middle-aged athletes, these individuals who might be a little bit more insulin resistant and see... Obviously, they're still training a lot, but obviously now they're a little bit older than our previous cohorts. So especially from a cardiomyotabolic health standpoint, how do they fare?

31:17
on the diet, right? This whole statement of, can you or can't you outrun or out exercise a poor diet? You're probably still able to do that when you're on your younger side, but what if you're now more, if you want to say middle age or what happens then? So that was kind of the whole gist or point behind that. Yeah. And I like it as well because that is the reality for a lot of us. And I know with

31:46
clients I see and other people I work with is that they've sort of gone on the premise that I'm an endurance athlete, I need carbohydrate, and here are the recommendations of 90 to 120 grams of carbs an hour. I'm really going to try and push my limit here. Whereas the health implications of that are not often thought about. And I've seen many athletes who actually fall into that category of athlete, which you found in your study.

32:15
when they adhere to that higher carbohydrate diet, which actually wasn't overly high. Well, it seemed high actually. The amount of carbohydrates seemed high, but if you broke it down into the categories of what the ACSM might recommend, these athletes were only consuming about five grams per kg body weight per day. That's about right, eh? Yeah. If you do a relative calculation.

32:44
If you did that calculation, then I'm going to go with that. From a gram standpoint, it was about 400 grams per day. Percentage standpoint, it was over 60%. Yeah. They're not numbers which are out of the realm of...

33:05
possibility for a lot of athletes who would be following a high carb diet. Can you sort of talk through the major finding that you found from that metabolic health perspective, Philip? Yeah. So, one thing that was really interesting is we did CGM. So that's continuous glucose monitoring. So that's something that is being used, obviously, traditionally, kind of more of your clinical populations, people with type 2 diabetes, right?

33:32
But now general population is becoming very interested. And obviously also athletic populations has become very interested. And you've seen even obviously professional athletes using it, experimenting with it. How does this maybe optimize their training or how does this change their fluid strategies, diet, et cetera, et cetera, et cetera. So in any case, yeah, so kudos to Levels Health, who was the company who...

34:00
who sponsored their technology and the CGMs for that study. That was a 31-day dietary intervention. So 31 days low carb, 31 days high carb. It's a crossover trial, so meaning each participant in that study, again, did both diets. The cool thing about crossover trials is if each person in the study undergoes all the experimental conditions. It's not just...

34:29
It's unlike a lot of other designs where you're in this group, now you stay in this group. Crossover designs, you get to crossover. So 31 days of either diet and CGM at the same time, so then you can see the glycemic response.

34:49
Right. So instead of, right. And that's a neat thing about CGM, right. So instead of just pricking your finger and knowing your blood glucose, now it's like, well, I can, I can track my blood glucose continuously, right. Throughout a 24 hour time period. And so that's obviously very valuable data. There's really not a lot out there on athletes. I mean, there's, we can literally count on one hand, the amount of, you know, basically CGM studies on athletes. So more.

35:17
more of that needs to be done. So it was very interesting. If somebody wants to see the graph, you can go look at the paper. But yeah, I mean, average blood glucose, median blood glucose, blood glucose variability was higher on the high carbohydrate diet. Or put another way, obviously, it was always much lower on the low carbohydrate diet. Or if you go look

35:47
across the 24 hours and 31 days, average blood glucose on the high-carb diet was close to 100 milligrams per deciliter. So that's basically, you're playing with that threshold of prediabetes. And then on the low-carb diet, average blood glucose was I think about 85 milligrams per deciliter. So again, it's the mean, it's the median, the variability, all reduced on the low-carb diet.

36:16
The other thing that was really interesting is that 30% of our sample entered this pre-diabetic lysemic phenotype on the high carbohydrate diet. Meaning their blood glucose was so elevated on the high carbohydrate diet, not just during the day but also nocturnally as well. At night as well, they met that pre-diabetic...

36:44
phenotype, which is blood glucose between 100 and 125 milligrams per deciliter. So I thought that was very interesting. And actually, if you have the individual data set, which I had, you can see that there was a couple other people who was very close to meeting that criteria as well. They were basically one cookie away from...

37:10
from also falling into that category. We found it was 30%, but just knowing the data and looking at the individual data, it could have been close to 50% or 60%. Did it make a difference, Philip, whether they did the LCHF first to then go on to the high carb or did it not make a difference, the order of the diets as to-

37:38
We obviously randomize them, so it's kind of balanced in terms of where they go. But not a single participant's blood glucose was over 100 milligrams per deciliter when they were on the low-carb diet. Okay, so when they were on the low-carb diet, nobody had that pre-diabetes. Or put another way, when those subjects transitioned from the high-carb diet, when they had...

38:07
they met that prediabetic glycemic phenotype, then when a low-carb diet, it was just reversed. Yeah. Yeah, yeah. So there was, again, there's clearly something going on there. And like I said earlier, because we control for calories and training and body composition, you go, well, what's going on here? It's not like their training is different or somebody's losing or gaining weight. They're highly athletic at the same time. So what's going on here? Why?

38:35
Why is 30% of these highly trained athletes developing prediabetes on the high carbohydrate diet? Obviously, unknowns to them, right? I mean, if it wasn't for doing the study, they wouldn't have known. Exactly, they wouldn't have known. We published a review, and kudos to Andrew Kutnick, who for that review, he pulled...

39:01
a lot of CGM data from other similar studies. Like I said, I think it could only find five. And actually we did two of the five. And yeah, it's interesting. So obviously the populations are different. One study was I think sub-elite, one was elite, others recreational, right? So the population differs, but it seems that if you kind of average it out, it's like that 30% number seems to hold in a lot of cases. In some cases, it's even much higher.

39:31
But again, hang on a second. These are all supposedly healthy individuals, very physically active. They're not overweight or obese. They're actually very lean. So why is, let's just say it's 30%. Again, obviously we need a lot more data to say what exactly is the number of athletes who develop pre-diabetes. Again, what's going on here? It looks like it's, like I said, just preliminary findings that...

40:00
It seems that some of these athletes are not tolerating the high carbohydrate diet that well, so some seem fine, right? So some seem fine, no issue, but it seems that certain subset are having issues. And obviously that's impairing their cardio metabolic health in the long term. And because of course you excluded participants who had diagnosed metabolic conditions. So this would have been a surprise, I guess.

40:29
you guys as well. Do you know what the diets were like going into the study, Philip? How different was the high carb to what they would normally have? Yeah, I mean, I don't have empirical data on that, but just talking to the athletes, they're all on the high carb diet before.

40:54
Now, how close of an exact match was it to, obviously, the diet that we prescribed from then? I'm not sure. It's probably not too different just based on conversations I had with them. Because, I mean, in these studies that we do, it's easy for the athletes to do the high-carb diet because they're already used to doing the high-carb diet. It's more education is needed when they switch over. Obviously, that's more of a challenging.

41:20
the dietitian is coaching them on how to do it, right? Completely different way of eating for them than obviously what they're used to. Yeah, and I guess, you know, a major sort of takeaway that I got from that study, which almost reaffirmed what I see in clinic as well, is that not everyone is suited to that high carb approach. And particularly as you age, metabolic health is a concern. So it's not. So just to think that you can blanketly

41:49
consume high amounts of carbohydrate because your training doesn't hold for a significant portion of people. Yeah, exactly. So, we've shown in that, I think, very novel study that low carbohydrate diets can definitely be used as a therapeutic strategy for helping to manage and lower blood glucose.

42:14
especially for those athletes who might be at risk for diabetes, who are more insulin resistant without impairing their performance, right? Because obviously then you have to add that last piece to it as well, right? Without impairing your performance. Yeah, yeah, that's true. And we haven't really talked about performance in this study. Although, am I right in thinking that those people who were metabolically more challenged, did they actually reach a higher peak fat oxidation in?

42:42
your study as well. They actually almost had the most gain from following the low carb approach. Yeah, there was an interesting correlation association between those variables. Those individuals that 30% with the hyperglycemia, but again, they switch over to the low carb, they also see the biggest improvements. Definitely something going on there that hasn't been explored yet.

43:12
these very high, if not record high, levels of fat oxidation. They also had a lot to benefit. Yeah, totally. I can't recall reading this actually. You might not have been able to do this, but any idea of visceral fat content and how quickly that can change and whether... Is that an area of interest for... Yeah. We haven't done that.

43:39
We have obviously very interesting and obviously there's a lot of other people who've looked at low carb diets and specifically body composition and visceral fat. That definitely seems to be a great strategy for reducing visceral fat. But yeah, we haven't measured that in any of our studies or at least not yet. Again, usually the, again, because we're bringing in these, and we work a lot with athletes,

44:09
These individuals are pretty lean. We don't see much changes in body composition. Usually we use biological impedance for body composition. It's not DEXO or Botpot, unfortunately. For these different dietary studies, I haven't seen... Again, they're already so lean, so I'm not seeing many people like, oh, this person's gaining weight or this person's losing weight. Yeah, totally. They're remaining weight.

44:39
Yeah. Yeah. No, I think I was thinking about visceral fat because the phenotype is higher, poor metabolic control, and you don't necessarily see what's going on on the inside. So hey, maybe something to look at in a future study. Maybe we just need to get more funding. There's always a way. Yeah. Hey, I'd love to just...

45:07
chat a little bit about your work looking at distance runners and lipid profiles. Do you remember this study that I'm thinking about with the, again, it was low carb versus high carb. Can you sort of chat to us what you did, what you found? Yeah. So that was published in the journal Nutrients. Not less.

45:36
Yeah, I think it was last year, I think 2022, if I remember correctly. And again, that's with some collaboration from Jeff Volick's groups at Ohio State University. Particularly, he's one student, he's one grad student, Alex Buga, so kudos for him for helping with the write-up for that paper. And so yeah, for that, that study is basically was a kind of a spin-off to one of our first studies looking at

46:03
low carb, high carb, six weeks on 5K performance. Now, what we also did during that study is we did some blood work. Then also to assess what's happening to their blood lipids and lipoproteins during this intervention period. Again, based on a spin off from this discussion we just had, it's not just about performance. How is health also being modulated?

46:33
by these diets. We're just talking a lot about obviously blood glucose. Obviously, that's a big story. But then you also have these other cardio metabolic factors and these kind of more cardiovascular disease risk factors. We looked at I think it was total cholesterol, LDL cholesterol, HDL cholesterol, VLDL, so very low density lipoprotein.

47:00
blood glucose, HbA1c, so glycate, hemoglobin, and then also some of the ratios like triglyceride, HDL ratio, et cetera. We've done two studies looking at that. Basically what we find is that the low carb diet is increasing total cholesterol, LDL cholesterol, but also HDL cholesterol. Just remember, this is in athletes.

47:30
So it's total cholesterol goes up, LDL cholesterol goes up, HDL cholesterol goes up. But then also at the same time, the low carb diet is deep. So that's what it's increasing. It's also decreasing usually like we just talked about blood glucose or decreasing triglycerides, decreasing VLDL levels at the same time, decreasing the triglyceride to HDL ratio. So this is interesting. No, I'm not a lipidologist. So I'm not going to...

47:59
I don't know all the specifics there, but it does present an interesting conundrum in this field of... Just looking at those factors, those lipids and lipoproteins, does this represent an increase or decrease risk in cardiovascular health? The answer to that question...

48:27
just depends who you talk to, right? So you have a lot of people in the low carb camp will say that cholesterol is not a very useful predictor or that's not so important. So all the other stuff is going in the right direction, so therefore decrease risk. Then obviously the traditional view within the field of, especially medicine and cardiovascular medicine is the whole lipid hypothesis. So

48:56
which centers around cholesterol, particularly aldehyl cholesterol, ApoB, etc. So they will look at that and go, no, that's an increased risk because that went up on the diet. To be truthful, I don't think we know. There's been a lot of work on this topic, again, in your clinical populations.

49:21
how much of this has been done in athletic populations, right? So athletes who are training who are manipulating their diets, especially now somebody who goes low carb, and they see increases in total cholesterol, aldeol cholesterol, but they also see all these other improvements as well. What do we tell them? Is the effect neutral? Is there risk on up? Is there risk on down?

49:50
So I'm more in the boat that their risk is going... If you look at their overall risk, it's decreased. If you're looking at cardiometabolic health and cardiovascular disease, your total atherosclerotic cardiovascular disease risk, I think there are many variables to look at. I don't know why we get stuck on one or two. So again, if you're a fan of the lipid hypothesis, you usually get...

50:19
just get stuck on LDL. Okay. Well, that's one variable. What about HDL? What about triglycerides? What about VLDL? What about the person's body composition? What about their, like you're saying visceral fat, right? What about their fat mass, fat-free mass? What about their systolic blood pressure, diastolic blood pressure? What about different clotting factors like

50:48
And then you can also do specialized testing, where you can actually see, like you do NMR testing, you can actually see the different particle sizes. So instead of just reporting LDL-C, you're reporting LDL-P, you're reporting the different LDL sizes as a pattern A, as a pattern B. You can do similar testing for HDL.

51:12
Yeah, I mean, there's so much to look at. I mean, all of those different factors, and I'm sure there's a bunch more that I did not mention, right? All those factors are important when you're having discussions about cardiovascular disease. So not sure why we're just focusing on one when there's so many others. And usually a lot of those other factors tend to move in the right direction on the low carb diet. But again, is more research warranted on that topic? Probably. Of course there is.

51:42
Yeah, and hopefully more people will do it. But definitely I think that means if you are an athlete and you're listening to this and you do go low carb, right? I mean that just warrants, right? Just kind of seeing for yourself how all these markers are changing. Yeah, for sure. Because there's been other people have published, I think it was earlier this year, Nick Norowitz and his group. The Lean Mass Hyper Responder. Dave Feldman.

52:12
Yeah, exactly. There's that idea and there's definitely some, or there appears to be a certain percentage of individuals. They didn't look at athletes, right? But the same can, I guess, be said for some of these athletes where they do see big increases in their LDL levels. Again, so at what point does it become problematic or not? I'm not sure.

52:41
Just from our one paper, and I'm just looking at some of the data here from that study. When they were on the low-carb diet, just to give you some of the numbers, their total cholesterol on the low-carb diet was 197, on the high-carb diet was 153. You can see that was about a 25% increase, but 197, so for total cholesterol, the demarcation line is 200. They're still below 200.

53:11
That's not too bad. For LDL, again, this is LDL-C, not LDL-P or not looking at different sub-particles. On the low carb diet, LDL-C was 108 milligrams per deciliter. On the high carb diet was 74. So sure, it was lower, like a 40% lower on the high carb diet, but on the high fat diet was 108. Well, that's not- It's not overly high, is it? That's not high.

53:41
Yeah, usually it's like dyslipidemia is like 130, so they're still well below the whole threshold for dyslipidemia or at least how it will be defined. So you go, well, if those two were concerned and you look at the paper, you go, well, yeah, sure, it was higher on the low carb group, but if you look at the numbers and you go, well, it doesn't even meet the definition of dyslipidemia. No. And then obviously you see the other benefits with triglycerides and HDL.

54:09
That's why I'm saying that I'm more inclined to say they're benefiting, but each person obviously has different responses and should evaluate that. Yeah, for sure. I found it really interesting. The other interesting thing I noted was that when you measured ketone production in the bloodstream, it didn't appear that those who were following that 50 grams of carbs,

54:36
or below, which is quite low for an athlete. It didn't appear that there was a lot of presence of ketone bodies in the bloodstream. So I guess my question is, is that even a really good marker of a ketogenic diet in an athlete if they're utilizing, I'm assuming, I don't know, are they using the ketones for fuel and therefore we're not going to see them in the bloodstream? What are your thoughts around that, Philip?

55:05
So why, for example, in athletes, you don't see very high levels of nutritional ketosis. Nutritional ketosis is usually defined as blood ketone levels between 0.5 and 3 millimollars. In the one study we did, the six weeks, it averaged out about 0.5 millimollars across the six weeks. So that's not...

55:33
very high. And in the other study, I think it was 0.7 or something like that, just a little bit higher. That was four weeks intervention. So again, I know from some of those athletes in a study, they went slightly above one. But again, if you compare those averages to some others, again, other studies, not on athletes, you see-

55:58
greater states of nutritional ketosis. The idea here is, especially for these athletes, obviously they have higher energetic needs that obviously those ketone bodies are being utilized. Obviously, they can be and is being utilized, whether it's by the muscle tissue, cardiac tissue, and obviously also by the brain as well, which means, as you were saying, that's just why you're seeing lower levels in the circulation.

56:28
That's sure. It's still one biomarker. And the nice thing about a low carb diet, right, that you can actually measure that. So it's still a biomarker, but just understand if you're an athlete, if you're like, hey, I'm doing everything right, right? And it's not as high as you might expect. That's probably the reason why. But right, if you want to see if you're fat adapted, so sure. That's...

56:56
obviously one way to see what's going on. But another way, right, and obviously what we do in our studies is you come into the lab and we do these testing on you, right? You can do, as long as you have a metabolic card, you use indirect calorimetry, right? You have the mask on and you're measuring oxygen consumption, CO2 production, and yada, yada, yada. You can measure rates of carbohydrate to fat usage. So now you come in and you do one of these tests, like a graded exercise test. Let me see.

57:25
Let's calculate your rate of fat oxidation. And obviously, if somebody's been low carb for a couple of weeks, a month, et cetera, we want to see that big increase for like here was baseline or you're on your normal diet and now here's what it is, at least say like a doubling effect when they were on the low carb diet. So obviously that's another good biomarker that you can look at, well, if that's possible, if you have access to a lab or somewhere to get tested.

57:54
Yeah. And also go out for a long run. Do you bonk? No? You might be better adapted. I don't know. I hear other people saying that's not a bad field test if you don't have access to a lab. Well, exactly. Subjective, right? So, I mean, you see how you're feeling. Some people say, well, they feel more energetic. So, I mean, obviously the subject of experience to the diets.

58:20
Like RPE, right? Rating of perceived exertion, affect. That's all important, I think, as well for those kinds of conversations. Yeah, for sure. And Philip, just finally on that study, you did look at performance? Oh yeah, yeah. For that one, yeah. That was for 5K. So that was an interesting one. Obviously, 5K, very...

58:47
Very popular race. A lot of people do 5K recreationally. And we got a good group of, again, recreational runners. I mean, one guy even qualified twice for the Olympic trials. But they were all very decent runners. Just a recreational runner. Yeah. But most of them were doing it in sub-20. Now, again, somebody might come back and say, oh, well, that's not elite. They're not doing it in 12 or 13 minutes. Well, sure. But again, they're still.

59:16
The representative of a competitive recreational athlete. Exactly. Very respectable times. And the neat thing about that study is we tested their performance actually quite frequently. So we did performance testing on day four, 14, 28, and 42. So basically almost like every two weeks we performed another 5K. And that's also for somebody listening to this. Like if you want to...

59:45
I mean, it is a pain, but instead of just doing pre and post testing, and if you want to do something more frequently, you get kind of an idea about the time course of the adaptation as well. And that's also actually something that's already needed in this field as well. But yeah, I mean, from a performance standpoint, it was very interesting. When they were on the low-carb diet, again, this is a crossover trial. So again, each participant did each diet.

01:00:13
they were on a low carb diet, their initial 5k performance, which was on day four, was slower. So it was significantly slower on the low carb diet on that first 5k, which is interesting because people report that. So you have anecdotal evidence about, hey, I'm a couple of days in, a week or so, and keto flu, or however people describe it.

01:00:39
They see this as their body is switching over fuel sources and they go through this adaptation period. Some people are seeing a decrement in performance. That's valuable information. Probably don't compete during that time period. But then, day 14, we didn't see a statistical significant difference in performance. However, let me just grab the paper here quickly. I want to look at the mean difference. The mean difference

01:01:09
was, they were still 32 seconds, so let's just say 30 seconds, they were still 30 seconds slower. So again, that's not statistically significant, but you go 30 seconds slower. That's quite a bit over 5K. Yeah, exactly. So maybe you can make a case for, from an applied or practical standpoint, two weeks, not that great as well. And then day 28,

01:01:39
Day 28, there was basically no – I mean, if you look at the – sure, there was no statistical significance, but even if you look at the means, it was like five seconds or four seconds, something like that. There was really no difference even between the means at day 28. Then day 42, they're actually 12 seconds faster on the low-card diet. Again, this is not statistically significant if you run the p-values. So, each two weeks, they got a little bit faster.

01:02:07
So very interesting, right? So initially, the performance was impaired, and then a little bit faster, a little bit faster, a little bit faster. And now we stopped at day 42, six weeks in. Would have been interesting to see what happens at, say, week eight, week 10, week 12. But overall, performance, basically not impaired. And that's for, obviously, a high intensity, short duration endurance events. And they ran at about 82% of their VO2 max.

01:02:37
Do you know, Philip, it would have been interesting had you tested them at three weeks to align with the race walker study and then to see what it was like four or five, maybe that's for a future study. Yeah. I mean, yeah. But a good point, but either way, I think we can even get some idea from that study that again, showing that first, again, because a lot of studies in this field, it's either a couple of days or a couple of weeks, that's probably not optimal. Yeah.

01:03:07
Totally agree. So I love chatting about this stuff, Philip, and I think it's really relevant because most of us are that competitive recreational athlete who actually just want to do our best but also be in good health as we do it. You did mention another study sort of in the works. Can you, to finish up, can you just give us any idea of some of the other research studies you're looking at that we can expect from your lab over the next couple of years?

01:03:36
Yeah. So like I said, we got funding and we're about to start this new study looking at this concept of bonking and hitting the wall. Obviously something if you're, especially an endurance athlete you're all familiar with, but you think about, well, has this actually been studied well? So it's not something that actually there's a lot of research in, especially

01:04:05
from a low-carb perspective. So again, we're doing that again on triathletes. So if anybody should be aware of hitting the wall, it's those individuals. But yeah, so we're doing a trial. And there's a lot that we're adding. So it's not just looking at, it's basically time to exhaustion trials.

01:04:28
So it's that. It's a, yeah, sure. It's performance or in this case, endurance exercise, specifically cycling endurance exercise performance, comparing high carb to low carb diets. And as I mentioned earlier too, we are administering different drinks during, as you can imagine, during the event or during the time to exhaustion trial. But we're experimenting with not how much...

01:04:56
Because that's been looked at, right? So this idea of just giving a large amount of carbohydrate during those events, but how little? What we're thinking is it's probably much lower than what most people think. Basically what I'm trying to do, I'm trying to feed these people just enough glucose to maintain their blood glucose level. Yeah, yeah, yeah. Right? And so that's kind of the idea. Again,

01:05:25
We're doing CGMs as well at the same time. Also looking at maybe who becomes hypoglycemic, where does that happen, when does that happen? We're also then reversing the possible hypoglycemia with a large bolus of carbohydrate to see what impact that has. Then the participants will do another time to exhaustion trial.

01:05:55
So they actually do two times the exhaustion trials. The first one, until you can't go any further, at about 70% of their VO2 max. And then once they reach this exhaustion, we give them a larger bolus of carbohydrate to reverse the hypoglycemia. And then they have to go again about 20 minutes later. Obviously, this is going to be a much shorter bout. But I think a lot is going to come out of that study. And I think it will be very valuable, especially

01:06:24
This is for more endurance athletes, especially those experimenting with their diet. That stuff, again, we're working on now. That should hopefully be done within a year or so. We also do a lot of other work on ketones, exogenous ketone supplements.

01:06:44
And so we do that a lot with other, you know, collaboration with other people. We're actually doing a study right now looking at chronic exogenous ketone supplementation on exercise performance. We're doing some other follow-up work looking at acute interventions as it comes to different energy bars. So for example, high-carb energy bars versus lower carbohydrate or higher fat energy bars.

01:07:12
So yeah, I mean, that's kind of the stuff that we've, you know, or at least some of the stuff that we're kind of currently working on with a lot more hopefully planned down the line. That sounds awesome, Philip. And in fact, this morning I was just talking to Heal Poffey, I think it's how I say his last name, about exogenous ketones and sleep and recovery. So super interesting field. Can you let us know how, so obviously I will put links in the show notes to the studies that we talked about today.

01:07:42
listeners get a heads up on your research? Yeah, I mean, I'm not too good with social media. I haven't been doing that great with social media. So I mean, I am on Twitter. So I don't know what my Twitter handle even is. But if you type Philip Prince, you'll find my Twitter or should find my Twitter profile. And again, sorry, I'm not.

01:08:09
that active, but I usually do try to post, hey, here's a study we just did and here it was just published. So that's probably the best place to kind of, if you're interested in this kind of stuff and just trying to see any new work or publications. Now our collaborators that we work with, like Professor Tim Noakes from South Africa. Andrew Kroenig. I'm also actually originally, yeah, yeah, yeah. Andrew.

01:08:38
Diego Steno, those guys are pretty active on social media. They obviously also share a lot of the work that we do. Those are some good people to check out as well. Yeah. No, that's great. I was going to say that. You, of course, you're originally from South Africa, Philip. Is that how you are involved with Professor Noakes and things like that? Was that just a coincidence? Yeah.

01:09:05
No, that's a big part of the connection. I grew up there. I came to the States in 2005, I think. I came on a tennis scholarship, so I played tennis competitively. I actually saw him when I was much younger. I had problems with

01:09:30
with cramping and my parents forced me to go see Professor Nocso. He was a sports scientist and obviously physician in Cape Town, which is where we lived. I forgot even what he said and what advice he gave me. That was too long ago. We connected a while ago.

01:09:56
When he switched over, I think a lot of people are familiar with his story, when he switched from promoting high carb diets to low carb diets, kind of soon after that is when we became connected and I told him, I'm starting to do research in this space and we started to collaborate. And a lot of the stuff we talked about now in this podcast, we worked very closely together.

01:10:24
the study design, making sure we have some novel and highly impactful studies. That's awesome and clearly successful in that space because these studies were great. Philip, thank you so much for your time this morning, your afternoon. I really appreciate it. Yeah, thank you very much, Miki.

01:10:56
Alright team, hopefully you enjoyed that as much as I enjoyed chatting to him, and of course I certainly am a fan of thinking about metabolic health, particularly as we age, and of sort of dispelling the notion that it doesn't matter what you eat as long as you train, because we now know that that, well we have known probably for a while, but this is just further evidence that that's just not the case. Alright then, so have a great week, next week on the podcast I-

01:11:25
to Peter Stirling about the allostatic stress response. Such a great conversation with the renowned expert in this field. And don't forget that Monday's Matter Registration closes this Friday, 22nd of September. So if you were looking for a way to sort of jump start your health goals coming into this next season, now's the time to join up. Alright, you guys can catch me over on Instagram,

01:11:55
@mikkiwilliden, Facebook @mikkiwillidenNutrition, head to my website mikkiwilliden.com, sign up to MondaysMatter. Alright, talk soon.