00:00
Hey everyone, it's Mikki here. You're listening to Mikkipedia and this week on the podcast I speak to returning guest Dr Philip Prins. Philip and I discussed his latest study that has pretty much just been published investigating the role of carbohydrate in endurance performance. We discussed the obligate role that we think carbohydrate plays but also what is the real purpose of

00:29
taking carbohydrate whilst training and whilst racing. the most recent study with Philip and his co-authors including Andrew Kutnick and Tim Noakes and Dom Dagostino really highlights or really challenges the notion that we all need at least 60 grams of carbohydrate if not upwards of 90 to 120 grams of carbohydrate to improve performance.

00:55
Philip and I go into that and the rationale why. We talk about the crossover point with regards to fat oxidation and carbohydrate oxidation. We discuss what I did in my ultra and of course what Hubster did as well. And we talk in broad terms, if you like, about fueling for the athlete and particularly endurance athlete. And we talk about health implications too. So those of you may remember that

01:21
Philip was on the show in September 2023 and I'll pop a link to his earlier podcast where we also talked about a range of studies including higher intensity exercise for ketogenic athletes. And so we talked a lot about his, the studies that were running there and the metabolic health aspect too. Dr. Philip Prinz is an associate professor of exercise science and he earned a bachelor of science in kinesiology as well as an MS in exercise science from Georgia Southern University.

01:51
and a PhD in exercise physiology from the University of Pittsburgh. His research focuses on, amongst other things, the practical impact of lifestyle on metabolism and how metabolism impacts health, disease, and performance outcomes. So among his many areas of interest and expertise are nutritional ketosis, metabolic responses to exercise, and sports nutrition. And I have put links to, in addition to that previous podcast, where you can find

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Philip at his university and also his research gate which has his profile and other papers and the study and question that we're discussing today.

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I'd like to remind you though, before we jump on into the conversation, that the best way to support this podcast is to hit the subscribe button on your favourite podcast this morning. Super excited because of course our previous conversation was based around health markers and metabolic markers associated with triathletes and the potential impact of a higher carbohydrate approach. For some of them, and of course now,

03:01
You've just recently published with your co-authors a paper that looked at the different amounts of carbohydrate and I guess what they do during exercise, which is what I am really excited to talk to you about today. Yeah, absolutely. Thanks for having me. What I will say actually, I just did an ultra run last week. It was 264 kilometres over seven days. And you can imagine there are a variety of

03:30
like fueling strategies that people use, like there are about 80 of us. And I would say that probably Hubster and I were on the lower carb range. We were taking in probably about 25 grams of carbs an hour, running for about four, between three and a half to 13 hours a day. And what I noticed actually was probably in the latter part of the week,

03:59
I felt like I needed a little bit more carbohydrate than what I did at the start of the week. Which I don't know, whether that is something which you would expect given the different pulls of fuel that we've got on the body or... Yeah. That's an interesting observation. What was the reason you decided to go with such a low amount? Well, it wasn't actually...

04:29
I suppose, it sounds weird because of course I'm a nutritionist, so you would have thought I had a plan. But we were like, well, what do we normally take when we're out training? And normally I do something like goo chomps. I have a gel or half a gel and then another half of the gel maybe 20 minutes later, just because it's easier in my stomach to sort of titrate it in. And actually to your question,

04:54
from a lot of what I've been looking at, I suppose, sort of thought leaders in this space is that what we want to do is titrate in amounts of carbohydrates to prevent hypoglycemia, which is, because I've seen Prof. Noakes, who was one of your co-authors, talk about that quite a bit over the last maybe couple of years. so I guess that was probably one of the Russianels, which is why we weren't slamming down 90 grams of carbs an hour. And also I was thinking,

05:23
how is my gut going to handle that like a higher intake of carbohydrate for many, many hours across the course of the event? And I didn't think that it would. And then finally we had like a weight limit. So there wasn't like, we had to really think about the, the, food intake and what we were actually able to take. Yeah, no very, yeah, it's very interesting. You know, cause I mean, I'm assuming most of your competitors were probably ingesting much

05:53
larger and much higher amounts. mean, that's obviously the dogmatic view within the field of exercise science and sports nutrition is that, as you call it, carbohydrate is the preferred substrate and fuel and you have to ingest a lot of them before exercise and obviously also during exercise, after exercise, et cetera. And if you look at the more latest sports nutrition guidelines, it's usually somewhere

06:20
between about 60, 90 up to 120 grams of carbohydrate that needs to be ingested during exercise because of this idea that it is going to spare your muscle glycogen. Is that actually the case? Does it spare muscle glycogen? There is evidence that paradoxically that no, it does not. Yes.

06:48
very interesting, right? So this notion that you have to ingest, Obviously, especially for endurance athletes, such a large amount of carbohydrates during exercise, again, based upon this belief, right? That muscle glycogen is essential. It is obligatory, right? In terms of exercise performance. And once your muscle glycogen

07:14
hits a certain level, right, becomes depleted, hits a very low level, right, then you're going to bonk, you're going to hit the wall, right, so to speak. And so, therefore, right, you want to maintain high rates of carbohydrate oxidation during exercise and you want to spare your muscle glycogen. so, therefore, the strategy, right, to ingest such large amounts during exercise. However, like I said, right, could it potentially, is there any evidence that suggests that it could be sped up?

07:44
And there is. There's a study by Holey and colleagues where they looked at, again, it was endurance exercise. It was like 70 % VO2 max for basically for about a two-hour duration. And subjects either ingested, I think it was like 120 grams of carbohydrates per hour. So again, a very large amount or just a placebo. So nothing.

08:15
And again, there's metabolic effects of ingesting such large amounts during exercise. So number one, their rates of fat oxidation fell quite significantly. mean, when they were ingesting or just on the placebo condition, their rates of fat oxidation was closer to about one gram per minute. When they're ingesting this large amount of carbohydrate during exercise, it was like

08:41
know, 0.2 or less than 0.2 grams per minute. So very low rates of fat oxidation. The metabolic effect of that is on the placebo using a decent amount of fat for fuel during exercise. But now by ingesting such a large amount of carbohydrate, now you have to switch. So where's the energy coming from at that point? So now you have very high rates of carbohydrate oxidation taking place and very interesting. So in that study,

09:09
If you compare muscle glycogen usage between the placebo and the carbohydrate condition, muscle glycogen usage was 70 % higher with the carbohydrate ingestion compared to the placebo. So like I said, it is paradoxical. We've been telling athletes that this strategy is going to spare your muscle glycogen, but evidence that this strategy can actually speed up muscle glycogen usage.

09:37
And is that because fat oxidation is suppressed so much that we then have to turn to this stored carbohydrate? interesting. And did it make a difference for that? I don't know if you, because I didn't even have questions about this on the little questions that I sent you through, so I know this is off the top of your head. But do we know what type of typical diet that these athletes consumed in the Hawley study? Or actually does it not matter? Are we going to see this?

10:05
whether or not it is an athlete who may be more fat adapted, for want of a better term, if there is one, versus just a standard sort of carbohydrate-fueled athlete? Yeah, so that study, like the vast majority of all the other studies in this field, athletes are ingesting their habitual diet, their habitual diet being some kind of moderate or high carbohydrate-based diet.

10:31
And again, I just add to that, obviously, when you do that, right, the outcome, whether it's pre-exercise or obviously also during exercise, the effect is still somewhat similar, right? I mean, and you see it in all the studies, all the studies that we have done. Most of the studies that we have done, is the pre-exercise diet is either higher in carbohydrate or lower in carbohydrate.

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does it have a metabolic effect? Of course it does, right? So obviously the athletes who are consuming lower carbohydrate diets, have high or very high rates of fat oxidation, but low rates of carbohydrate oxidation, right? And then it's the opposite, right? For when they switch over to the high carb diet, now their rates of fat oxidation plummet and their rates of carbohydrate oxidation is higher. So yes, the pre-exercise diet results in that, but then obviously

11:28
depending on what is being ingested during exercise, obviously has the carbohydrate that is being ingested, the amount that's being ingested is going to have potent metabolic effects as well. And so yes, obviously the, you're doing the recommended amounts, 60, 90, 120, absolutely. mean, the, the, the, the insulin spike that comes with that, Is this going to significantly, right? Impair.

11:57
lipolysis and fat oxidation, which if you look at our study, and I'm sure we're to talk about that here in a little bit, it was a very small amount. It was only 10 grams. That's why I was interested in, so during your ultra, you're doing 25 grams per hour. Now we didn't study 25 grams per hour, but something very similar to that, right? At only about 10 grams per hour. So what we found there, I mean, the 10 grams per hour had very

12:25
There was a reason that was chosen. I piloted that extensively to make sure that it had very, very minimal metabolic effects during exercise. I'm probably the same thing with you, Asol, but now as you start going up, you'll see greater and greater metabolic effects with carbohydrate and fat oxidation rates. Okay, so this is a real 101 question, and absolutely we're going to get back through to sort of what you found with your...

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with your study and we're going to go into that in detail. is there an insulin spike during exercise? Yes. I mean, we haven't measured that, but you can imagine, absolutely, if I'm ingesting, let's say, 10 grams of some kind of carbohydrate source, and usually the most of the carbohydrate sources, maltodextrin, sucrose, glucose, et cetera.

13:21
is going to have that glucose spike, an excursion followed by obviously some kind of insulin elevation as well. So absolutely, you're going to see that happening to a much greater extent if I was ingesting 60, 90, 120 versus just 10. Yeah. No, Or something similar to that. Yeah. Yeah, that makes sense. And I guess the other thing with the ultra endurance sort of space like

13:51
I feel like there hasn't been a lot of research on that sort of six, seven, eight, nine hours of activity. A lot of the endurance or long duration tends to sort of top out at two or three when we're thinking about the studies that really inform some of these sort of guidelines. mean, there are more case studies looking at ultra marathoners. And I do know that there are some super elite

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ultra marathoners who do manage 90 grams of carbs an hour over eight or nine hours. And I do, but I also think that they themselves are very good athletes. There's just something special about them to be able to sort of really perform high at their sport compared to me who's just a middle-aged enthusiast. Yeah. mean, when we're doing the research, right, most of this research is happening, right, within a lab-based setting.

14:48
I mean it's hard to go for these sessions to last more than three or four hours. So whether it's our work or the work of others or even if you look at the historical research on this topic, whether it is just manipulating individuals pre-exercise diet or their muscle glycogen stores, right, pre-exercise, or obviously any kind of carbohydrate ingestion strategy during exercise. I mean there's not many studies

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that go beyond say a three or four hour limit. So absolutely at that point in time, you can go look at certain case studies of individuals doing some kind of dietary strategy beforehand or again, also obviously during hand. For example, our colleague in South Africa, Sean, Sean Sokinowski, he's an endurance cyclist.

15:46
And so, but you know, Sean, so if you follow him on social media, he's an interesting individual. he has been low carb or carnivore for a long time. I don't know if we're going to how many years. But much longer than the duration that we put people on dyes for these studies, right? Just a couple of weeks, right? So he's been low carb carnivore for many years now. And

16:16
And he posts regularly on social media or for example, if you follow him on Strava or something like you can see, right? So he's going out for very long duration rides. you know, whether it's three hours, four hours, five hours, eight hours, nine hours, and he's doing it with, so during the ride, you know, he's just doing water and some electrolytes and that's it. Isn't that crazy? Yes. Yeah.

16:45
Equally though, you'll be familiar with Prof. Paul Lawson, I imagine. And Paul and I have spoken about how he field tests his athletes to get a sense of their fat adaptation by sort of getting them to ride up to five hours with just water and electrolytes. it's like, you know, that would send alarm bells ringing in most sort of sports nutritionists' of or coaches' heads. you know, it's such a good...

17:13
way to assess how well the body can utilize other fuel sources. Yeah, absolutely. mean, that's again, so individuals, he's not the only person. So individuals like him make for great case studies to examine substrate utilization and maybe also your chronic adaptations. Since as you can imagine, right?

17:41
for the studies that especially that we have done in our lab is usually ranges somewhere between four and six weeks. And obviously there's metabolic adaptations that take place during that time period. But then you look at someone like him and others who has been low carb or carnivore for much longer, right? Years. And so there's clearly other metabolic adaptations and

18:08
that's happening, biochemical adaptations, further enhancements in mitochondrial efficiency and other enzymatic adaptations that must happen that allow those individuals to do that. Yeah, no, I agree. And in fact, one of the things which I've spoken to Dr. Dan Plews about quite a bit is the fact that he was low carb for, and still is relatively low carb actually, for many, many years. And he talks about how his improvements

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like small but noticeable for him occurred over many years of being in that sort metabolic nutritional state compared to the likes of people who go on a low carb diet for three weeks and then try and go out and run a 10K run or walk a 10K walk or whatever. you're right. And I imagine that many of these things are a little bit not immeasurable because you can probably measure everything, but in this case study sort of arena, it's hard to pinpoint exactly.

19:04
Yeah. mean, so there's absolutely a lack of longitudinal data. So when it comes to, you know, specifically athletes adapting to low carb diets for, you know, chronically over long periods of time, right, months or years, I mean, just, there's just very little data on that. mean, Jeff Volak, I they, at Ohio State University, they published a study some years ago, I think it was about 2015.

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on those ultra-endurance runners. But that was not a randomized controlled trial. Those are individuals who are already habitually consuming a high carb or low carb diet. And I forget now the duration there. I think it was at least longer than six months or something like that. So then you look at that data specifically, I remember their muscle glycogen. So very interestingly, their muscle glycogen was not significantly different or

20:02
the muscle glycogen for the low carb athletes was not significantly different compared to the habitual high carb athletes. So is that a chronic adaptation? Yes. Yeah, it's interesting you mentioned that because I do remember someone almost questioning Jeff Volek on the accuracy of that information or data. I'm thinking, gosh, isn't that interesting because it doesn't fit someone's preconceived notion of what

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you would expect muscle glycogen and a low carb athlete B, they're going to challenge the finding rather than sort of go, oh, actually, well, that's super interesting. Well, again, there's a lot of studies that lasted a couple of days or a couple of weeks where muscle glycogen has been assessed, especially if you go back a couple of decades ago where this all started.

20:54
And with the muscle biopsy technique, right, the group of Scandinavian scientists, 1960s, right, who first came out with that. And then they started to obviously manipulate muscle glycogen by putting people on different diets. So again, a of those studies, right, a couple of weeks, oh sorry, a of days and sometimes a couple of weeks. And absolutely, so when you go look at those studies, those individuals who are on a low carb diet, but again, it's fairly acute, right? It's fairly short term. Right, their muscle glycogen.

21:23
their pre-exercise muscle glycogen levels were always significantly lower compared to those individuals consuming obviously a more moderate or mixed diet or obviously a high carbohydrate diet. So therefore that warrants further investigation. Again, this topic of what are these chronic adaptations? Again, we have a pretty good idea or at least a decent idea of what's going on.

21:49
couple of days, couple of weeks, up to a four week, six weeks, et cetera. But once we start talking about months and years, the data is really lacking. It's just so hard to do those studies. You got to find some really committed athletes who's going to want to do this in the long term. And that's so hard because so many of them have been led to believe that there's

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one dietary strategy that's going to improve their performance. And obviously then you need significant funding for something like that. Yeah, 100%. And Philip, before I sort of dive into your research, just, a question, is there any suggestion that if you are lower carb, that having, and you adapt to that state, that you're more sensitive to carbohydrate that you take in when you exercise, or is that wishful thinking? Remains to be determined.

22:42
Yeah, interesting. Again, so you're just at that point, right, again, there's no real data on that. you can find maybe certain individuals, again, on social media or again, maybe different case studies, but not any hard data on that, unfortunately. Yeah, okay. Because that's an interesting question in itself. Philip. Yeah, maybe, maybe not. Yeah. What actually led you to question the idea about muscle glycogen and ingested carbohydrate

23:11
are obligatory fuels for sustaining performance. Like what even got you down this rabbit hole in the first place? I don't know if I asked you that last time. All my degrees in academia, my undergraduate degree, master's and PhD, right, is in exercise science, kinesiology and exercise physiology. Always had a passion, very deep interest also with nutrition. So, you know, I've done, you know,

23:40
quite a few different, basically all of my studies is either related to how nutrition, whether it's diet or maybe even supplementation, right, is impacting health and performance. But from specifically talking about this specific space, low-carb and high-carb diets and how it's impacting metabolism and performance and just health in general, that started about 10 years ago or so.

24:09
and kind of my interaction and collaboration with Professor Tim Noakes from South Africa. Yeah, so I became interested in that topic so about a decade ago. And mostly because of him, because of Professor Noakes' basically paradigm shift that he had. So that intrigued me a lot or why somebody who has

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supported and advocated right for high carb diets for athletes right over such a long period of time. Why would he then change his mindset on that? And so that intrigued me and I started to dig obviously more into the scientific literature on that topic. And yeah, I just wanted to do our own study. So this whole idea about muscle glycogen and

25:06
You know, it's, is it essential or obligatory, right? When it comes to human exercise performance, or again, this idea that, that fat is a more inferior, right? Metabolic fuel unable to support high intensity exercise. So there's, there's, there's all kinds of, you know, different reasons and explanations for why obviously the field of sports matrician, right? Has this high carbohydrate mentality, right? Or if you were to

25:34
talk to athletes and you ask them what kind of diet does your coach or trainer recommend? Obviously the vast majority will say, obviously a high carbohydrate diet is needed to be ingested in order to optimize my sports performance. But I think very few athletes are able to articulate the actual reasons why.

26:04
Obviously, there's many different reasons why the field of sports nutrition has this high carbohydrate mentality, whether it has to do with increased user consciousness of healthier food choices. If you think back to the dietary guidelines and back decades ago and this idea that fat is bad and saturated fat is bad, or just the

26:28
The whole dietary guidelines, right? So therefore, right, or people see the food pyramid and go, I need to consume more fruits and vegetables and whole grains, right? Or the, this whole idea that fat burns in a carbohydrate flame, the whole anaplerotic theory that states, well, that basically in short, just goes well with my muscle. If I'm running out of glycogen,

26:55
So my muscle glycogen stores become depleted. That in turn is going to result in less TCA cycle intermediates. then therefore as a result, it's going to impair the mitochondrial stability to oxidize those fatty acids. So therefore fat burns in a carbohydrate flame. Or whether it's all the studies over the last couple of decades showing carbohydrate ingestion during exercise improves exercise performance.

27:23
or especially pivotal studies done by certain individuals showing that low carb diets impair exercise performance. These are all reasons. I think though the big ones definitely pertain to this glycogen centric view of exercise performance and the whole crossover concept. think especially in my field of exercise science, if you look at the textbook or just kind most of our... Those are kind of the two big, I think, teachings.

27:53
this idea that exercise intensity has a big impact on energy flux, carbohydrate and fat oxidation. And if you're doing more higher intensity exercise, or if you progress from moderate to high intensity exercise, you're not using a lot of fat for fuel, using mostly carbohydrates for fuel. Therefore, this idea that carbohydrates, especially for, because most athletes are doing more higher intensity

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whether it's during training or obviously during a lot of specific competitive events, it's usually above that crossover point. higher rates of, or we would say then the exercise is carbohydrate dependent, The carbohydrate dependence of high intensity exercise or this whole idea that fat is a more inferior metabolic fuel. And then the whole glycogen centric view of exercise performance, like I said, that goes back decades ago by the

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work from a Bergstrom and colleagues when they measured muscle glycogen, right, in athletes consuming either high-carb diets, moderate-carb diets, or low-carb diets. And depending on their diet, the carbohydrate content in a diet that obviously heavily influenced their pre-exercise muscle glycogen. So the higher the carbohydrate content in the diet, the higher the pre-exercise muscle glycogen, and therefore the greater

29:19
the longer, right? Or the better the endurance exercise performance. So, this kind of quote unquote link or correlation between muscle glycogen, right? And endurance exercise performance. So, we're saying there that the pre-exercise muscle glycogen content seems to be a determining factor when it comes to human exercise performance. But then the

29:46
pre-exercise muscle glycogen content in turn is determined by the carbohydrate content, right, off the diet. again, so if you understand those two teachings, and I'm welcome to go into them in more detail if you want, but most people who are in this field have heard about that. So if you understand those teachings and those models or those theories, then absolutely you understand then why over the course of the last 50 years we've been recommending

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and guiding athletes to consume obviously a lot of carbohydrates before exercise or also during exercise. And that also therefore explains at the same time why we've been recommending athletes to not consume diets that's obviously lower in carbohydrate or obviously as we talked about at the beginning of this, why not to consume 10 grams or 25 grams as you did right during that endurance event.

30:44
what we've been doing over the course of the last, I don't know, six, seven, eight years is to test these different hypotheses, right? And to challenge these different theories, these different views. And you think about it, it's really not that hard to do. Now, there seems to be a general lack of interest within the scientific community, right, to test these different hypotheses, but it's actually not that hard to do.

31:13
you would just, I mean, if you want to kind of look at the first teaching, fat is an inferior metabolic fuel and able to support higher intensity exercise, okay. Just get a, again, group of athletes, again, adapt them to high carb, low carb diet for a couple of weeks. And then, well, do some high intensity exercise.

31:41
Exercise. Right. Let's what happens. Because if it's true, well, obviously, in those cases, the alpha is who are consuming a low carb diet, as we said also earlier on in this conversation, they're going to have obviously lower rates of carbohydrate oxidation, much higher rates of fat oxidation. But now they're doing a high intensity exercise event that's supposed to be carbohydrate dependent. So their performance should be impaired. So again, not that hard to to design some kind of study.

32:11
to see if that is indeed true in the context of a low-carb athlete. And you've done that. Yeah, absolutely. And other researchers have done it as well. And what astounds me actually, Philip, is the lack of acknowledgement of these studies that disprove that theory. Like even this morning, I was listening to a podcast with a very well-known sports nutritionist who was pretty adamant, him and...

32:36
his exercise physiology buddy who's now become some sort of guru in this space saying you absolutely need carbohydrate for VO2 max above like 60 % or something. I'm like, this is just crazy. Yeah. Yeah. So we've done, we've again assessed performance. So just specifically for the more higher intensity events or again above that crossover point, which again for most athletes, right, it's above about 60, 65 % or off their VO2 max.

33:04
We've looked at maximal endurance exercise performance or VO2 max or time to exhaustion during a VO2 max test. We've looked at a five kilometer running time trial performance that was performed at just over 80 % VO2 max. done, we've looked at one mile time trial performance. So that was done about 90 % or so of VO2 max. We've done repeated sprints. So 800 meter sprints specifically done at about

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85, 86 % VO2 max, but again, a whole series of them, basically like a repeated sprint protocol. Okay, so in none of those studies did the low carb diet impair exercise performance. Yeah, that's super interesting. Philip, wanna, before I crack on into your latest study looking at that 10 grams of carbohydrate, can you just, I guess, dispel for us that carbohydrate

34:03
that fat burns in a carbohydrate flame, because I do hear that a lot. And you described what that actually means. what do we know that actually disproves how you explained it? Yeah. So I remember learning that right in grad school, I think. And again, it's another, because there are many, as I just went through a little bit ago, there are many different reasons and explanations for why

34:32
for why we tell athletes to consume high carb diets or avoid low carb diets. So again, just to summarize the idea there, so especially during more longer duration events, that's moderate or high intensity, but not for a longer duration, because obviously in that particular context, you're significantly lowering or depleting your muscle glycogen. And so when you're doing that, the idea is then therefore,

35:02
you're reducing glycolysis, right? So anybody who's taken an ex-phys or some kind of biochemistry course, right? So what's the input to glycolysis? Well, basically carbohydrate, right? And okay, so now my carbohydrate fuel tank, my glycogen is running low, so I have reduced glycolysis. Now I have reduced pyruvate that comes from glycolysis and then therefore as a result,

35:27
I have reduced these Krebs cycle intermediates, these products within the TCA cycle that basically keep it going and functioning. And therefore as a result, now we're saying, well, it doesn't matter how much fat you have to burn. It doesn't matter that you have this enormous amount of energy coming from fat. If it's 50, 60, 70, 80,000 kilocalories coming from your fat stores, fat also burns in a carbohydrate flame, meaning

35:56
know, fat also gets oxidized right within the Krebs cycle within the TCA cycle. So that's that particular theory. But again, doesn't seem to, not all the facts seem to line up, right? Because of that, just think about it. So if that is indeed true, and I was, we're actually talking about this in my ex-phys class the other day.

36:21
Like if that's indeed to think about it. So now you get a low you an athlete right who's on a low carb diet That individuals again muscle glycogen is obviously now significantly lower compared to what it is on a high carb diet So again, we can we can test this it's not that hard. Yeah, put the athlete on a low carb diet And now say go we'll do some kind of you know endurance event

36:49
According to that theory, that athlete's endurance exercise performance should be significantly impaired because now they start out the exercise with much lower levels of glycogen within their muscle, which means, oh, it shouldn't take that long for them now to deplete the glycogen that's in their muscle. Now, again, it doesn't matter the fact that this person is such an incredible fat burner, right? All the fat, right, also has to get oxidized, right, or go to the Krebs cycle. Therefore, again, clearly there should be...

37:19
an impairment in endurance exercise performance. But when you go look at the studies or again, the one that we'll talk about next, because we haven't just looked at the more shorter duration, higher intensity exercise performance, but we also looked at endurance exercise performance. And again, no difference there, no impairment in performance either. So maybe that applies to athletes consuming high carb diet, but it doesn't seem to apply to athletes consuming.

37:48
a low-carb diet. Yeah. so, Philip, you mentioned earlier actually that there were reasons for you choosing the 10 grams of carbohydrate an hour, which did seem like super tiny. How did you arrive at that number? Okay. Yeah. So, for that study, just to maybe even back it up a little bit. Yes, please.

38:17
And again, if anybody's interested or want to go read the actual study, I mean, that was published in the American Journal of Physiology not that long ago. you can find it on... I'll pop it in the show notes. yes, that will be good. But yeah, so we wanted to... After doing a whole series of studies, right, that was more shorter in duration, lasting basically anywhere from

38:44
right? A couple of minutes to about, you know, 15, 20 minutes, right? For the 5K stuff. Um, we wanted to do something more, uh, obviously longer in duration. And again, the idea is that there should be a clear difference. There should be a clear difference. Specifically, sure. You know, um, this, uh, this anaplerotic theory of fat burns in a carbohydrate flame, or again, just back to this idea about, well, muscle glycogen is all about how much glycogen right is within your muscle. And once that reaches a certain point,

39:14
Right? During exercise where it's very low, you're going to bonk, you're going to hit the wall, right? Those feelings of fatigue, right? Your RPE is going to be going way up or your AFEC is going to be going way down. So, therefore, you're going to slow down or stop, therefore, as a result. And again, just say everybody can understand. So, if you're on a low-carb diet, usually just for a couple of weeks, again, maybe there's evidence for...

39:41
Maybe some kind of chronic adaptation where your muscle glycogen is not lower, but for the most part, the majority of the evidence says that it is. So especially in the time course that we're studying it, a couple of weeks. So if you just think about it, my muscle glycogen is lower. I'm starting the exercise compared to athletes who are starting the exercise where their pre-exercise muscle glycogen is much higher because they're consuming a much higher carbohydrate-based diet.

40:11
So therefore, as result, now during exercise, maybe after the first hour or so, right off of performing exercise, now my muscle glycogen has now hit a low or very low level. And therefore, again, according to that belief that muscle glycogen is obligatory or plays some kind of causal role, right, in fatigue, then absolutely you should see a significant difference, right?

40:38
those athletes consuming the low carb diet and high carb diet when it comes to endurance exercise performance. But again, that's why we do research. So in this particular study, we got a group of triathletes. they're all doing the Ironman triathlon. So these are individuals with a very high training volume. They're biking a lot, they're swimming a lot, they're running a lot, etc.

41:09
So we put them so as for six weeks, so six weeks duration, high carb, low carb, it's a crossover design, right? So each, meaning each person in the study undergoes each intervention and that was randomized. Now, So can I just ask, Philip, was it six weeks on the high carb, washout, six weeks on the low carb? Exactly. And then just the order was mixed up, right? We randomized that. Yeah.

41:36
Okay, and then six weeks, was that just to ensure that actually these athletes were going to be well adapted to their dietary intervention? Whereas there are some questions if you only put someone on a diet for say two weeks, whether or not that's enough time. So is that why you were like, look, let's just be super safe, do it six weeks? Yeah, so based on our previous studies, we have shown that that range, four to six weeks, or at least four weeks, right, is...

42:04
is sufficient to not impair exercise performance. So therefore that particular kind of study duration. And can you just remind us when you say LCHF or low carb, are we talking about under 50 grams of carbohydrate a day, protein consistent across diets?

42:26
And like, so how did that look? Yeah. So from a dietary standpoint, when they were on the low carb diet, so specifically they're consuming a ketogenic diet, so less than 50 grams per day. If you go look at the, there's a table in that study where you can go find all the, you know, kind of the averages, the six week averages for the low carb and high carb diet. But yeah, so when they were on a low carb or the ketogenic diet, they were consuming on average about 40 grams.

42:55
of carbohydrates per day compared to when they were on the high carbohydrate diet, they were consuming on average about 400 grams of carbohydrate per day. So kind of a big difference there in overall carbohydrate. So basically from a percentage standpoint, less than 10 % on the low ketogenic and about 60, 70 % of carbohydrate on the high carb diet. So if I'm thinking 400 grams of

43:24
that might be six or seven grams per kg body weight or some, or at least over five grams per kg body weight for these particular athletes. Yeah, but either way, significant difference, like only about like a 400 gram difference in the amount of carbohydrate that's being ingested on a daily basis with that. So again, think out that.

43:49
will influence specifically muscle glycogen. I'm only consuming 40 grams versus I'm consuming 400 grams per day. Isocheloric, so were the calories the same? So if there was a weight bump in the high carb diet, that would just be because they were storing more glycogen and more water. So it wasn't like...

44:09
that no one gained or lost weight on those? Yeah, it's isochloric. I think it was like 2,500 or so kcal per day. But yeah, we try our best. Obviously, this is hard to do in these studies to control for obviously confounding variables. So making sure the overall total calorie amount is roughly the same.

44:35
Or for example, training, right, training volume. Obviously, if there's any significant changes in that, that can impact performance. So by controlling calories, by controlling training volume, or for the most part, even body composition, so you obviously don't want to see big changes in there, you're looking at the end of the day, right, what we're interested in is diet-induced effects. Right? That's why we do these studies, right? We want to see...

45:00
how diet ultimately is impacting performance, not some other variable. Any diet adherence issues like, or so the low carb, were, or the ketogenic, were in ketosis. I mean, hey, if someone can eat 400 grams of, I mean, that is a feat within itself, but I mean. Yeah, so we have a nutritionist that works.

45:26
with each athlete or each participant in the study. there's education and sessions, fulmarization orientation, right? That happens before the start of each diet. We use, for that study, we use MyFitnessPal, right? It's just easy, it's convenient, right? People have the app on their phone.

45:53
and then they log their dietary intake at least three days per week. most of these individuals like doing it on a much regular basis. Triathletes for you. Yeah, so they do that. The nutritionist, so, because at the end of each week, right, we put the data into the system, the nutritionist or the dietitian is looking at that or making any adjustments if adjustments, right, are needed. Then there's also

46:22
We give each participant the little blood ketone meter. they're measuring, obviously on the low carb diet, they're measuring their blood ketones a couple of days per week. Also for that study, we did a CGM, so continuous glucose monitoring. And I have access to the platform and that was through Super Sapiens, which has since gone out of business, but anyways. But we have the, so they give access to the...

46:49
to the platform and so I can see each participant their daily values. if somebody were to cheat, Well, so meaning- would see it. Yeah, whether it's the dietician is seeing it or I'm seeing different or I'm not seeing significant elevations in their blood ketones or obviously if they have the sensor on, right? And they're in a low carb diet and their blood glucose is going right all over the place or significant elevations, right? So-

47:15
So we can see it. So that's kind of our way to make a sheer adherence because we have those systems and protocols in place, adherence to the diets is always good. Yeah, nice one. Did you measure muscle? Do you do muscle biopsies on the glycogen? No. No. So unfortunately we did not. That is obviously a little bit more challenging. You don't see a lot of people do that these days anymore.

47:45
Obviously, it is an invasive procedure. And if you are going to do it, obviously, you're to have to have individuals or participants who are willing to have a little hole in their leg before they start to exercise. But then also after, you have to do it after exercise as well, Because it's pre-exercise and then, or measure it again, right? At the point of exhaustion and...

48:13
But subject recouping for these studies are already significantly challenging. And so you don't want to introduce another variable. So therefore, look at other studies, similar in duration, and you look at muscle glycogen that was assessed in that. So sure, no study is perfect. And we're not saying our studies are perfect. And that is a limitation, that we did not directly measure glycogen. However, based on obviously other previous studies of

48:42
summer protocols and similar duration on low carb, there should have been a pretty significant and stark difference there. Yeah, sure. So Philip, can you want to chat through what you found or what you did actually and what you found beyond the diet intervention? low carb, high carb, six weeks. so what you're looking there is, again, how does the pre-exercise diet impacting, in this case, endurance exercise performance?

49:09
And so for endurance exercise performance, we did a time to exhaustion trial. So these athletes were on a bike and they were going at about 70 % again off their VO2 max to exhaustion. so if for those who are unfamiliar with it, a time to exhaustion is just pretty similar, right? So here's your, there's a, we calculate, so a power output that corresponds with that

49:39
VO2 max range, and then basically you're just holding that workload until you can't hold that workload any longer. And then that's it. That's your time to exhaustion. And so that was one part of the study. How does the pre-exercise diet impact endurance exercise performance? And so in that particular trial, I mean, did they, it was time to...

50:08
time to exhaustion and there was no carbohydrate ingested during that challenge. Yeah, so that's one aspect of the study. The other aspect of the study was then carbohydrate ingestion during those sessions. Yeah, okay. So when they're on the low carb diet or high carb diet, during those time to exhaustion sessions, they either received a placebo

50:36
or again, the carbohydrate, but again, the 10 grams per hour. So again, there's different elements of the study here, right? Basically what we're trying to, it was not many, this is the first study I think that was designed in such a way to get an idea of, is it muscle glycogen depletion?

51:00
that's causing fatigue, right? Or is the principal driver of fatigue or is it something else, right? Or is it exercise-induced hypoglycemia? And we can talk more about the history of that later on if you want. So that's how the study was designed. Because if you think about it, if the pre-exercise diet,

51:28
Right? Low carb or high carb. And again, that's having significant alterations in muscle glycogen. If we're seeing no differences in exercise performance there, well, then you would step back and go, well, how's muscle glycogen then obligatory? Or, yeah, exactly. How is it so essential? How is it having such a significant impact on performance if we're feeding people 40 grams versus 400 grams of carbohydrates on a daily basis? Right? And we're seeing no significant difference in...

51:57
in time to exhaustion. And that's exactly what happened. There was no significant difference there. But then the other thing we did is, the carbohydrate ingestion strategy during exercise. And participants were blinded. They didn't know what they're getting. So it was every 20 minutes. That was the protocol that we did. So every 20 minutes during the time to exhaustion, it's either, here's basically just flavored water.

52:25
or here is a very small amount of carbohydrate. Now in that case, it averaged out to be about three grams every 20 minutes, so it comes out to about 10 grams per hour. So again, a lot of pilot testing went into that beforehand because we wanted to choose a carbohydrate ingestion strategy that would not significantly have any impacts on metabolism.

52:52
Right? Because that's usually what, again, as we talked about previously, absolutely once the carbohydrate intake during exercise is higher, right, then you're going to see some big shifts there, right, in carbohydrate and fat oxidation. So based upon our, our previous pilot work, it was shown that, okay, this is having very minimal impacts on metabolism during exercise. And, and so now, right, so the idea there is

53:21
this small amount is going to have a minimal impact on substrate metabolism during exercise. And this minimal amount, will it be sufficient? Right? Because the idea is that this will help to maintain blood glucose concentrations during exercise. It will help to mitigate hypoglycemia during exercise based on this idea, right? You only have a very small amount of glucose, right, in your bloodstream. It's only about four or five grams of glucose right in five liters of blood.

53:50
So again, that was the other idea behind this 10 grams per hour, right? What would be a small enough amount that would not impact significantly substrate metabolism, but would be at the same time be sufficient to help maintain glycemia, help maintain blood glucose concentrations during exercise. And that's where we did see a difference. Okay, so can I ask a couple of questions?

54:19
What type of carbohydrate were they ingesting? Was it multidextrin, glucose, or? And my other question is, actually answer that first. Yes, it was the first one you mentioned. It was multidextrin, yeah. Okay, multidextrin, yeah. And then, is the strategy, the sort of 10 grams or the titration of very small amounts of carbohydrate, is that very similar to the carbohydrate rinsing strategies that we've seen being used in other

54:48
studies that look at the impact of very small amounts of carbohydrate on the brain and work output. And I believe these were studies done in cyclists. Yeah. Maybe 10 or 15 years ago. Maybe there's some, well, I can imagine obviously there's some differences and similarities, know, as well as where, again, I haven't personally done any carbohydrate rinsing studies, but again, interesting how you have seen performance benefits, right, of just, you know, rinsing with carbohydrate, right?

55:14
during some of these events and seeing improvement, right? So obviously indications there of some kind of central brain mechanism. Now with these, with what we're doing, right, is more geared towards the small glucose pool, right? The amount of glucose in your bloodstream, within your circulation, within your liver. Because sure, once your blood glucose starts to go down, right, mean, clinical hypoglycemia is below 70 milligrams per deciliter.

55:44
right? The person's going to start to experience symptoms of fatigue, right? And again, so that's why I'm saying there are similarities there, going back to the central or brain mechanism, right? Because your brain is trying to prevent glycopenic brain damage from occurring, right? If there's insufficient amount of glucose going to the brain. So this goes back to, for example, Professor Noakes' central governor model, right? Of fatigue, the brain is kind of preventing

56:14
that damage from occurring. therefore, as a result, you start to experience more more greater symptoms of discomfort and of fatigue. Now, historically, we would say, well, that's because your muscle glycogen has hit very low levels. But again, there's evidence, as we have shown in this study, because this study was specifically developed to single out those two.

56:41
And what we have found in that other part of the study is there was a big difference in performance. So independent of diet. So it didn't matter if was subjects were on the high carb diet or low carb diet. When they ingested this very minimal amount of carbohydrate during exercise, they saw about a 20 % improvement in performance. Because you can see if you go look at the blood glucose values, again, it's in the paper, there's a big difference in the post exercise.

57:09
So the point of fatigue, that point where like, okay, I can't maintain this power output anymore. Why? Well, we measured blood glucose immediately post exercise and there's about a 20 milligram per deciliter difference compared to when they were ingesting, Again, only minimal, only 10 grams per hour compared to obviously zero, right? Or just flavored water.

57:38
So absolutely again, evidence that it's rather exercise-induced hypoglycemia that seems to be a principal driver of fatigue, not so much muscle glycogen depletion. And that, so just for anybody listening to this, once you understand that, there are significant implications of that knowledge and we can talk more about that. Let's talk about them. Yeah. What are these

58:07
So again, remember, first off, we've shown now in a couple different studies that the pre-exercise diet, it doesn't seem to impact exercise performance, right? High carb, low carb, whether it's shorter duration, more middle duration or long duration. Again, if there was a difference, if all these theories or teachings are correct, I should have, in all of these studies, we should have seen a clear difference, never.

58:35
never any difference. Okay. So it doesn't seem that pre-exercise diet seems to be a determining factor when it comes to exercise performance. Sure, it's impacting muscle glycogen, but whether it's high or low doesn't seem to have any meaningful difference when it comes to exercise performance. I mean, if you even think about the other, one of the previous studies we did just very quickly,

59:02
We did repeated sprints, 800 meter sprints. That's a glycogen depleting protocol. We did six of them. Yeah. Because you can deplete your glycogen in this example that I just cited. That's okay. It's long, longer duration. But you can also deplete it very quickly by doing very high intensity exercise, right? Doing multiple sets. And that was kind of the purpose of doing that, right? Because the idea is, now the subjects are on the low carb diet.

59:31
They're coming in, that was only four weeks study, they're coming in with low levels of glycogen in the muscle. So, maybe here by the third or fourth set, right? Oh, their glycogen is now going to very low levels, right? Because intensity is such a big factor, right? That really accelerates glycogen usage and depletion, right? Accelerating glycolysis and obviously glycogen also is taking place within the muscle.

59:56
And so that was the idea behind that protocol. But again, that didn't happen. You go look at performance for the 800 meter sprints for all six sets. So no difference there. Actually, in that study, we measured the higher rates of fat oxidation ever recorded. So very high rates of obviously fat oxidation that humans can achieve on that diet, even at high exercise intensities. But any case, I digress.

01:00:24
The point there is we've done multiple studies, obviously others have as well, just showing that the pre-exercise diet seems to have a minimal impact on exercise performance. That's valuable information because then you can choose for yourself. It's not just this kind of... You must be low carb or you must be high carb. It's like, hey, what do you prefer? Yeah. Obviously, it's from a historical perspective, oh, you must consume a high carb diet.

01:00:52
in order to optimize your performance. So this one size fits all protocol. Because the other thing, and it's obviously also helpful information for any listeners is in all of these studies, yes, there are individual differences. As you can imagine. So you have to just, when you look at these studies and you look at the, you're looking at the means, you're looking at the averages. Oh, there was no difference in one-mile time trial performance or time to exhaustion, 5K, whatever. You're looking at the means.

01:01:20
But what you don't see is usually like the individual performances and how one person did better on the high carb diet and how the other person did better on the low carb diet. So for example, the study I was just referring to, the time to exhaustion, there was 10 subjects in that study. Guess what? Five did better on the high carb diet, five did better on the low carb diet. So was actually an equal split. So that's obviously just something that everybody can test out for them.

01:01:50
for themselves because there is those individual differences. maybe as we discuss later, but obviously then the health implications should be considered of those dietary choices as well. So there's dietary implications of that. However, the other big implication is if we're saying that it's hyperglycemia, right, exercise-induced hyperglycemia,

01:02:18
is more closely related to fatigue or what we refer to as bonking or hitting the wall and not so much glycogen depletion, that has significant dietary implications as well. Because if you go with the traditional view that it's all about glycogen, muscle glycogen is obligatory, it's essential for human exercise performance and metabolism, then absolutely you would ingest

01:02:44
large amounts before exercise, To stuff your muscle with as much carbohydrate or glycogen as possible. Again, you would ingest the large amounts during, right? To, you know, prevent glycogen or to spare it, right? Which doesn't seem to be the case either, as we previously discussed. Okay. But the other one, if we're saying, it's rather to do with, you know, drops in blood glucose levels. Well,

01:03:13
what we did in this study. It was only a very small, again, because again, you only need a very small amount of carbohydrate to help prevent or mitigate hypoglycemia. So therefore, again, the current recommendations up to 120 grams per hour, but we showed obviously just a minimal amount, 10 grams per hour is sufficient to do that as well. So

01:03:42
If you're following our research, basically there's significant dietary ramifications as it pertains to the diet that's consumed before exercise, but also the dietary strategies during exercise. Yeah. Philip, like at 70 % VO2 max, like do you think that your findings at that intensity is applicable to say a marathon runner? Like I'm thinking about myself running a marathon at...

01:04:08
potentially higher intensity. Do you think that the same theory would still hold? Yeah, mean, we think it would. again, obviously, the subjects we chose in our studies, or that particular one, right, was triathletes. And I mean, that's a multimodal type of activity. So it goes swimming, biking, and running. So we think, you know,

01:04:35
know, speculate that the results obviously goes to other right endurance sports as well. Now in terms of the actual intensity, right, that was about, you know, average out to be about 70 % of VO2 max. Now obviously, understandingly, depending on the event and the athlete, right, some individuals are able to maybe hold right 75%, 80%, right, VO2 max. So,

01:05:02
that with the intensity matter, well, I don't know, because then we look at some of the other studies we've done where on that crossover concept, and we have shown that athletes who are on a low carb diet, the crossover point occurred at 85 % of their VO2 max. Meaning at that intensity, that's 85%. I think that's pretty high intensity. was the crossover point. Meaning so at that point, 50 % of the energy was coming from carbs, 50 % of the energy was coming from fat.

01:05:32
Again, those who are on a low-carb diet, just know that you are shifting that crossover point to the right and you are using a significant amount of fats for fuel even at those higher exercise intensity. Now, obviously for those who are doing, like you're saying, a marathon, but the longer the duration, obviously the intensity is going to start dropping significantly. So, I don't think it's an issue there. It would still just be about, especially during those long duration events,

01:06:02
ensuring you are supplementing obviously with some form of carbohydrate, but again, to maintain your blood glucose concentrations. Yeah, okay. So, and I guess this is the thing, right? It's that is 10 grams an hour going to be enough to maintain that blood glucose concentration. But to your point, we've only, we've got, it's circulating amounts of four grams and five liters of blood. It actually should. Like I'm quite keen to even look at, cause we've got...

01:06:28
a marathon coming up actually in a few weeks time. It would be interesting to sort of test 10 gram theory and just see what happens because you've got nothing to lose really. Yeah, absolutely. I mean, obviously, people can test it out, for example, just during training, going on a long run or bike or something like that and see how they do. If you're used to 60, 90 or obviously any of these higher amounts,

01:06:57
Yeah, well, how would you do right on on much lower amounts? Right again, so we're obviously we just did 10 now. What's what's missing in this field is proper dosing studies. Yeah, proper dosing. Like testing different levels. Yeah. You would think that there would be more. There are not there. There hasn't been a lot of very well controlled studies where they say, okay, well,

01:07:24
How does 10 grams compared to 60 grams compared to 90 grams compared to 120, whatever? And that's actually where our research is going. So anybody who is interested, obviously, that's going to take a while to finish that. So I would say in a two to three year time period, we should have a sufficient amount of data on high carb athletes and low carb athletes. Because if you think about it, there's two different states.

01:07:50
So for example, if you're an athlete adapted to a high carb diet, what does it look like for my performance doing 10 grams per hour versus 60 grams per hour versus 90 grams per hour? But then how does that look like? Is that any different for a low carb athlete doing 10 versus 60 versus 90? Because you can imagine that the responses might be different there. And so we're planning to do those dose response studies and we're planning to do them.

01:08:16
in high carb athletes and also fat adapted athletes. And so we'll have answers to those questions. And I also like, just to throw another, not spanner in the works, but think about it, like, because you're looking at specifically like ketogenic athletes, whereas you've got the likes of, let's say, Hubster and I, and we have our diets were probably more in the realms of 100 to 120 grams. So still fairly low carb, like less than maybe 25 % of our calories are coming from carbohydrate.

01:08:45
but not in that ketogenic space. I wonder if there's a difference there as well. Yeah, I would go back to just what I said previously. It would seem that that pre-exercise diet has a minimal impact on performance. Now in your case, your carb intake is still on the lower end. You're not doing 400, 500, 600, or some of these elite athletes doing like a kilogram.

01:09:15
I heard that on a podcast this morning as well. went, whoa, that's a lot. So you obviously still have higher rates of fat oxidation that's obviously will be beneficial, especially during obviously those longer duration events. So again, I would go back just to that point that the pre-exercise diet is probably having very minimal impacts.

01:09:42
and rather maybe focus on what's being ingested during exercise. Yeah. I feel, and to your point about the health ramifications, and I'm mindful of your time, so I don't want to you too long, Oh, good. Because of course, just over in the last couple of weeks, the internet seems to have blown up over Lionel Sanders' realization that his really terrible shit diet that he really championed for years and years has finally, he finally got blood.

01:10:11
work done to show all of these symptoms were prediabetes that he was experiencing because of that. I mean, it really does blow my mind that athletes think that they can get away with it, actually. I mean, this was just one very public example that you just, a lot of us can't. Again, thanks for bringing that up, Because again, that's been something that's been...

01:10:35
If you're in this space, the nutritional space on social media, you've seen a lot of chatter recently about Lionel Sanders coming out, obviously elite triathlete and, well, I'm pre-diabetic. I don't want to die of diabetes. But if you go look at some of those videos, again, here's

01:10:58
carb intake was enormous. He was at about, I think he said like a kilogram, like basically per day. for, again, so that's not unusual for these elite endurance or ultra endurance athletes to be consuming such a large amount, right? Such a large amount of carbohydrate on a daily basis. And as he admits, right, it's coming, lot of the carbohydrates just coming from junk food, right? These ultra processed foods, a lot of just sweets and

01:11:28
and candies, cetera. So, kudos to Eam for coming out, for being brave enough to say that and express that. There's clearly a lot more, whether it's recreational athletes, semi-pro athletes, or obviously in this case, also professional athletes whose health is being significantly impaired via this diet. So that's what I'm saying.

01:11:55
The pre-exercise diet is not significantly impacting exercise performance. Okay. But that's one aspect. Exactly. you can't just, when you're doing the, when you're testing this stuff out, you're doing the NF1 experiments, right? It's not just about the performance aspects, but also about the health aspects as well, right? So the, when I was on, when we were chatting, I think it was, was it last year? Yeah, just 18 months ago or so. Then we were talking a lot about that previous study because we found that in

01:12:26
Again, in endurance athletes, in that study, was mostly, well, it was runners, but also cyclists, triathletes, marathon runners. 30 % were pre-diabetic on the high-carb diet. Nobody on the low-carb diet were pre-diabetic, but on the high-carb diet, on the traditional diet. So, again, despite to think about it, despite all the training.

01:12:54
despite those high training loads. And that was just in our study. I can't imagine, I mean, the training load of Lionel Sanders, right? The amount of training that goes into that. So despite all that exercise, still developing features, right, of pre-diabetes. And we did publish also, I think it was the last year or the year before, kind of a review article that kind of dealt with the crossover concept.

01:13:20
but also this topic of blood glucose and dysregulation and pre-diabetes. And again, so there are some other studies. There's not a lot of studies on this, right? For example, we've done CGM on athletes over a course of a couple of weeks. So some studies have actually found that number to be higher than 30%. Some of them have found it to be lower than 30%. What we do know is that a certain percentage

01:13:46
clearly our athletes are developing features of pre-diabetes and just overall their cardio metabolic health is impaired. Yeah, and I've seen a lot of the chatter on X about it and people are arguing that his symptoms or his poor health or blood glucose was as a result of, or his improvements, sorry, because now he's finally sleeping so it's not the carbohydrate. Because of course, one of the features of pre-diabetes is having to get up

01:14:16
to go to the bathroom several times a night so you can't sleep. I'm like, well, it's not just, yes, the sleep improved and obviously that's going to improve his performance, but the sleep only improved because he changed his diet. Yeah, I mean, your kidneys has to work overtime to, you know, filter and excrete all that excess sugar, right? Yeah, I know. And he is still eating carbohydrate, but he's making, like, I can, like, I didn't see any information on.

01:14:43
how much carbohydrate he's eating now compared to sort of what he was eating. But he was talking about doing something like having a full-on carbohydrate breakfast, then doing a super easy ride, but still consuming carbohydrate during that ride, and then consuming carbohydrate after the ride, you know? And these are habits that a lot of triathletes do use, particularly if they're lean, because I feel like athletes who might struggle a little bit with body composition have probably more awareness

01:15:13
of the impact of carbohydrate for that reason and probably a little bit lower, at least in my clinical experience. Whereas I get a lot of athletes who tend to, quote unquote, get away with it. So they're just like chowing down all the time. Yeah. And guess how long can you get away with it? Right. Because what happens when your training load starts to go down? Because again, we know exercise obviously helps to improve insulin sensitivity.

01:15:42
Right? I mean, you have, when you look at the mechanism, right, you have that insulin dependent, but then you also have that insulin independent mechanism, right, of a Glut4 activation or translocation. And that's exercise, right? Exercise and muscle contraction, right? Independently of insulin action causes the activation and translocation of those glucose transporters. But now, right, what happens later on, right, when the person is not training

01:16:10
so vigorously, so heavy anymore, right? And still consuming obviously a high carbohydrate diet, how would the person's long-term health then be implicated by that? Yeah, for sure. And I think that's why I asked you the question much earlier on just about that insulin response during exercise. in my, mean, to be fair, I haven't really looked at it that hard, but I was just under the assumption that

01:16:39
didn't really use insulin during exercise because we had these independent sort of pathways. I mean, usually the plasma insulin concentrations during exercise go down. But obviously, I'm going to, that response is going to look different, right? If I'm just exercising without ingesting anything, right? Or I'm doing exactly big difference there. Yeah. Philip, in...

01:17:06
I guess one of my final questions is on sex differences. Do we expect this to be different in females versus males? Are there any mechanisms that would suggest there are? Maybe, maybe not. Again, it's unfortunate that almost all of the research in this field is done on males. So yeah, sorry, I don't have a good answer to that question. Again, maybe.

01:17:34
Maybe, maybe not. It's just so hard to tell. And again, it is unfortunate that there are not more people interested in doing this work or research. if you think about all this stuff for the work that we've been talking about, there's not lot of labs just in the US, right, who's doing the research, right? Our lab, here at Gross City College, know, Jeff Olick's lab at the Ohio State University. And then it's like, well, who else is interested in doing it?

01:18:04
But yes, absolutely. That's much more needs to be explored within this realm. Like I told you kind of where more my interest or kind of future direction is going at. So now that we have kind of moved away from muscle glycogen, let's rather look at, know, carbohydrates ingesting during exercise and different dosing strategies. So yeah, that's just one little niche area.

01:18:31
that we need to study and investigate. But again, there's so many, right? There's so many. You're mentioning one, are there gender differences? Right? So people should investigate that, right? Or what about recovery? Well, how's training load or volume impacted? Right? How's immune function impacted? How's, you know, kind of muscle coordination or during your sports like tennis or cricket, but kind of more fine motor activities, how's that impacted by

01:19:00
copper hydra restrictions. So many, many more areas to explore. we just need more people to actually be interested and invested in this. Yeah. No, I love it, Philip. Thank you so much for your time, your afternoon, my morning. Like I loved doing this deep dive into it because it's an area that fascinates me because I know so many low carb athletes who are absolutely fine. I know so many athletes, male and female, that go out with not a lot of fuel.

01:19:28
they're actually absolutely fine. what I see clinically doesn't always marry up to what you see in the literature at all until now with the emergence of the research that you guys are doing. thank you so much for that. And go check in. Again, you're welcome to follow me on, or whoever's interested on social media or research gate and go read some of the studies.

01:19:55
But definitely, you know, stay tuned because we have some great work coming up or there's a very massive or big review article that hopefully gets published sometime by the end of this year that investigates the last 100 years of research on this topic and evaluates over 150 studies on this topic.

01:20:24
right? This whole idea, especially as it pertains to this small glucose pool, right? The amount of glucose in your bloodstream and the liver compared to obviously the much larger glucose pool, right? The glucose glycogen stored within your muscle. So, will provide a great historical context. Is anybody interested in the history? like I said, we go back, I last 100 years. It's very interesting.

01:20:52
Right, how the science evolved from like their studies you can go find in the 1930s. Where people were, again, the Scandinavians were doing some really excellent work or exercising for a prolonged period of time, seeing hypoglycemia develop, experiencing symptoms of fatigue, ingesting carbohydrates at that point.

01:21:21
being able then to exercise for more prolonged periods of time once the hypoglycemia is being eliminated. But then how that unfortunately kind of went away once the whole muscle biopsy technique was developed in the 1960s and then how most of the focus just kind of then shifted kind of away from exercise-induced hypoglycemia as a principal cause of fatigue.

01:21:51
then the end thing became muscle glycogen and being able to measure muscle glycogen and just that relationship between muscle glycogen and fatigue. But again, the last thing I would say is very interesting. If anybody wants to go look up that as a 1967 study by Bergstrom and colleagues, that pivotal study, right? And everybody always cites and there was really kind of the whole start

01:22:21
to this iconic and novel idea about muscle glycogen and its role in human exercise performance. You know what? They did measure blood glucose as well. It's just that people overlook that. It's just that, oh, look at this perfect correlation between pre-exercise muscle glycogen and fatigue, right? It's such a strong positive relationship between those variables and how diet impacted that, right? But they measured blood.

01:22:50
glucose. if you go look on the... Because there was three trials, right? It was the three different diets, low carb, moderate, and then high. In all three trials, significant hypoglycemia developed, because that was also time to exhaustion at I think 75 % VO2 max. So it was there. Hypoglycemia has always been there. When you look at all of these trials, that is...

01:23:17
know, where the exercise duration is longer than an hour or at least two or three hours in duration. Sure, the ones that measured muscle glycogen, right? So you'll see, sure, muscle glycogen is low, but blood glucose, right, is also low. And then you go look at some of these other studies, like I know Ed Koral did one, and I think that was in the 80s. And it was like some really exceptional endurance athletes. These guys

01:23:44
were doing either carbohydrate or placebo. And when they got the placebo, they ran for three hours. They did the carbohydrate ingestion, they did for four hours. So they ran an hour more just by doing, that case, it was like 100 grams per hour. But then you go look at their muscle glycogen. The point of exhaustion, right, again, three hours or four hours, right, that was the same. their muscle glycogen was basically, you know, identical. So then you go, well, studies like that, you know, just kind of

01:24:14
like our own one, like how can muscle glycogen be responsible or be directly kind of a causal agent there of fatigue, right? But then you go look at the data for the blood glucose and you see, oh, when they were ingesting the placebo, right, their blood glucose were starting to do this, right? They were starting to go down quite significantly. that's the, or seems to be rather the...

01:24:41
the driver of fatigue or one of the drivers obviously of fatigue for these endurance events. So that's kind of a little snippet, a little preamble there to the big review. again, it's a lot of work went into that. again, professor Tim Noakes kind of drove that effort. And so it should be a game changer when it hopefully comes out sometime later this year.

01:25:07
Well, Philip, I would love to get you back on to chat about it when it is published because that sounds amazing. And of course, I will put links to your research gate to, I will hunt down that 1960s trial because I'm sort of interested myself, pop that in the show notes as well. And of course, a separate link to the study that we focused on today too. good. Amazing. Thank you so much for all of the work that you do and also for taking the time to share it with us because

01:25:36
The is, that people will continue to repeat what they think is true because there aren't enough of these conversations happening. So I love that you see how important it is that we do it as well with the podcast. Yeah, absolutely. Again, thanks for having me on. Nice. Thanks for that.

01:26:06
Alright, hopefully you enjoyed that as much as I did and I'm super looking forward to that review that Philip and I were discussing that hopefully is due out later this year. I mean, the fact that it's a game changer for how we think about sports nutrition is huge. But I mean, fundamentally, there are so many trials that have now been published that really challenge these conventional views. I mean, know, Pluse is really big in this space, Paul Lawson.

01:26:34
I mean, there are just a whole bunch of people. So it's really great to chat to the people who are really sort of current in their information around sports nutrition and also care about metabolic health. So next week on the podcast, Speaking of Challenging Conventional Thinking, I have the pleasure of chatting to Nina Thaikulch all about the dietary guidelines and just diet in general. Super great conversation. Until then though, you can catch me over on

01:27:05
Instagram, X and threads @mikkiwilliden, Facebook @mikkiwillidenNutrition or head to my website, Mikkiwilliden.com. All right team, you have the best week. See you later.