Feeding Tolerance and Fat Oxidation in Ultrarunners with Chris Rauch B.Nut.Diet, APD, AccSD | Koopcast Episode 119

trail and ultra runners what is going on what's happening welcome to another episode of the KoopCast as always i am your humble host coach Jason Koop i'm excited everybody is here with me today this week we have another nutrition focused podcast it seems that that is the theme which is all very appropriate right now given people are ramping up their training for this year's upcoming races y'all will remember last week we spoke with meredith terranova about how to practically implement your racing and your training nutrition and this week we switch gears and we talk a little bit more about the science behind it this week's episode guest is christopher rush out of monash university and let me say right out of the get-go before i go any further monash has been absolutely crushing it in the research game over the course of the last nine or 12 months it seems like every week when i open up my inbox and i look at the pubmed searches that automatically get dropped into there there is something of tremendous value from monash so fist bumps and kudos all the way around to that group and it just so happens that a lot of their research has an ultra marathon slant and that is the subject of this week's podcast chris was the lead author on a brand new paper that examined the

feeding tolerance glucose availability and oxidation rates of ultra runners in response to prolonged exercise and one of the things i appreciated about this paper is that it challenged our previously conceived notions in our previous guidelines for how much carbohydrate athletes can actually take when they are out on these long runs and i do think that if you listen a little bit to this podcast and some of our previous guests that we have had about this subject one of the things that rings true is that we do need to keep a cap on how much we are eating and drinking out there on the course and it might fly in the face of some of the standard recommendations that are floating out there i will let the conversation speak for itself i hope everybody listening out there gets something out of this conversation i certainly did as a coach and it's something that i'm going to start to implement with my athletes as well so with that as a backdrop i'm going to get right out of the way here's my conversation with chris roush out of monash university i tell you what man you guys have been killing it over there at monash university like what is in the water there where you guys keep cranking out all this research i've got i was telling a friend of mine earlier today i have three different pubmed uh searches set up for different like keywords and things like that that i get auto dumped into it into my inbox you guys take up like 60 of whatever i'm

getting emailed so i don't know i don't know what to attribute that to um yes we uh yeah we have a lot of studies on and um yeah it's really just exploded like since our first uh first gut study that uh that we did um a number of years ago um it's just kept growing and growing and it just always seems to keep moving forward like we always um answer some questions but then a whole heap of you know new questions emerge and then we pursue those um one one uh yeah which which which brings brings a real problem for us uh with recruitment subjects yeah yeah i mean you know when you think about it uh there's only so many uh people that they're willing to run three hours on a treadmill in you know in a lab and have all this stuff done to them so um you know yeah that that is uh that is a challenge especially yeah especially at the moment you know coming out of the whole covid thing well i mean you've been in academia for long enough and i've been coaching for long enough to kind of realize that especially in an ultra marathon perspective or even if we use iron man as a little bit of a surrogate to that uh since it's more commonly studied the number of people that are willing to do something like that has has actually been on the rise i mean we you we can actually recruit people to run three or four hours on a treadmill or be on a bike for five or six hours where it seems like 10 years ago it was like

you know just you they'd look at you like you're an alien or something like that um well not not only that jason we we i mean i even get um paying clients to do this so um so out of our out of our research um we've actually developed um an exercise clinic so uh because so many of our um our participants from from research you know we gave them feedback from from our findings and they went on and won races you know or in the very least had big improvements um and we thought actually you know we should be selling this service so alongside the research we've also got the sports clinic where we um we use our research protocols um and um yeah and people pay a lot of money for it yeah and i i have an athlete that has actually utilized it uh as as as well and it's one of those things where i've just come to know just through this podcast and you guys's research um that i can trust what's going on there so i have no hesitation sending an athlete over there for whatever protocol it is whether it's a heat protocol or nutrition protocol or whatever because i've seen all the research and yes i realize that it's going to be you know that the protocols and things like that are going to be a little bit different in a commercial you know commercial application so to speak but i'm hard i'm i'm this is completely outside of what we're going to talk about that's totally fine i'm really heartened to see that because a lot of times there's this missing gap between academia and reality you know in terms

of what athletes are actually going to use and i like i i actually like seeing this this change where a lot of uh uh universities and and and research institutions are starting to also bring in this more i'm going to say the word commercial but people are going to get mad at me because it makes it sound bad or something like that but this more kind of commercial side to it where they're bringing in the public for like paid services essentially yeah yeah look absolutely and i mean yeah if you don't like that and i guess i have to qualify that when you when you say commercial um like you know and i say people pay a lot of money for it as far as the uni is concerned it really is just cost recovery you know we do it as a service but you know it is it's expensive to run a university lab um you know it's expensive to run the bloods and you know and and the time and everything and insurance and all the stuff that happens in the background so it really just costs recovery from us but as far as the exercise clinic is concerned the other thing i'd like to say sort of building on what you've said there is um one thing um a one direction a lot of research is taking is that it is more real world and and and the word you know the word they like to use is translational yeah you know it's it's all very well saying oh that's that's interesting but how does that apply in the real world yeah i've gotten not that i'm getting sick of it but i'm going to use that phrasing anyway i'm kind of getting sick

of the mechanistic studies like i just because i've just seen them so much i'm like okay i understand this biochemical pathway i understand that this is going to happen when you're metabolizing that and show me the real world application and we're starting to see it a lot in training right now is in like training interventions right so the whole polarized versus pyramidal training i had somebody on my podcast recently where we talked about that to that one recently yeah where and he and he's that's that's the way that uh luca is actually taking his research as well where there these pig training intervention designs which are complicated to get off the ground for a whole host of reasons but seeing what the actual practical outcomes are of hey this person's going to train like this they're going to do high volume this person's going to do low volume and we're going to see which one wins essentially i think that is the stuff that is ultimately cool at the end of the day yeah absolutely absolutely you know and when when you know when i read studies yeah you know saying we're talking about mechanistic stuff and you know a researcher studying some signaling protein or something and at the end of the day like yeah interesting and you know it gives us insight but i don't know how they do it to be honest yeah we could go on and on and on about that yeah absolutely needless to say man you guys are killing it so seriously you guys no you guys are absolutely killing it the volume of stuff that you're producing as well as the quality i've been i've been really impressed i don't know whether you're just getting on a lucky streak of covid or whether something there

is like changed within within like your team or whatever but the quality of the people that you guys have first off first and foremost i think is is is a good telltale sign you guys have really high quality team there but the research that you guys are producing is is is has been quite remarkable so i'm appreciative of it i wanted to start out just with saying that oh thank you yeah thank you very very much for saying that um i guess you know me i mean i'm uh i'm just a PhD student myself um and you know i really have to acknowledge um our dietetic and extremes physiology lead um professor ricardo costa um you know he really is the brainchild behind a lot of this um but yeah we are a fantastic team and we all you know work together you know in a really fantastic way so um yeah can you broaden that up a little bit before before we get into the paper that we're going to discuss very specifically i'd like for the listeners to kind of understand the team there and what some of the like the focus points of that team are we mentioned you know al mccubbin who's been on this podcast before and i'll leave a link in the show notes to that but can you just give a broad overview on some of the things that you guys are studying as a group yeah absolutely look our our biggest area interest is um gas uh exercise gastroenterology so um basically it is um how how the gastrointestinal tract or the gut responds to the stress of exercise um so we look at uh we typically look at um the

symptomology that occurs under exercise stress um how ambient conditions change that and affect it um we look at uh markers of damage so uh actual intestinal damage um and um yeah what what else can i say um you know and and yeah so we you know our research has uncovered pathways um for for these um uh so the term the term used is uh exercise associated gastrointestinal syndrome so you know it's there's no one causal thing um you know we've identified causal pathways um and um there's there's so much interest in it because we're now finding links to um to the clinical arena because we we have in our ultra marathon runners and especially in the heat um all this gut stress so um the the perturbations the damage etc but it's very close it very closely resembles what happens in a clinical state like if someone has um inflammatory bowel disease or uncontrolled celiac that sort of thing um and so yeah we're really branching out into diverse areas all related all related to gut which is really neat because normally it's the other way around right normally a lot of what we are informed about on the athletic side comes from the clinical side and i always use this analogy of the norma tech boots right which were

previously used for diabetic patients and trying to increase circulation with people with diabetes and all of a sudden migrated into the athletic field as a as a way to apparently recover more quickly or better after uh after hard workouts so the fact that you guys are doing an opposite fashion is actually kind of neat i can kind of summarize it like this though you guys put athletes in endurance athletes and and and ultra endurance athletes in arduous situations either via duration and or temperature and or feeding and you see what happens to their gut yes yes thank you summarize that much better than me i can like for a long time right no i see here's the here's the i have i have a little bit of an end since i've had an athlete that's gone over there the the way that she describes it to me is i went in this room and it was really freaking hot and they made me run hard for a long period of time and stuff food down my throat so that's a much better summary than my my uh yes yours is more clinical hers is more practical right um okay so we're the primary paper we're going to discuss and this is one that's kind of fascinating to me on a number of different levels um it's got a super long name so the listeners are going to have to like put through the i'm surprised anyone get i'll be surprised if anyone gets past the name the title of it is like yeah i'm giving you a lot of credit for producing good really good research but this title is a doozy i will link in the show notes so nobody has to memorize it but it's feeding tolerance glucose availability

and whole body total carbohydrate and fat oxidation and male endurance and ultra endurance runners in response to prolonged exercise consuming a habitual mixed macronutrient diet and carbohydrate feeding during exercise so that is an ultra marathon type of title in and of itself yeah just reading the title is an active yeah ultra isn't it really so let's try to boil this down like practically what are you practically what are you trying to what are you trying to distill out of the protocol well first let's just go over the protocol right what are you putting this what were you putting the subjects through and what data were you collecting okay so um it's essentially it's essentially a collection of studies all right so we we we've had um it was three studies um and uh you know there were there were some things that we saw in the data as as we were going where we're like gee that's that's interesting we really need to uh you know delve into that and and you know yeah put it out there so um what we're doing um should we just say sure yeah sorry should i talk you through sort of the three the three study designs yeah because you guys are getting to this as you were just alluding to you're taking data that was previously collected and you're getting and you're determining different things from that so you can get into what the three studies we're looking at first and then we can get into how this kind of alchemizes it second yeah okay so the first study was the original gut study we did

and that was um getting ultra runners so so first they do their um the incremental exercise test the vo2 max test and that really essentially is just the um uh the initial assessment for us where we can determine um this the running speed their steady state running speed and that is 60 percent of vo2 max so they run for three hours the first two hours they're they're running at the 60 percent of vo2 so so steady state you know for most of them that's um uh 10 10k an hour or six six minute um kilometer pace and during that two hours they're being fed um with some formulated gel discs so we actually made up these little jelly blocks or discs um and that was 90 grams of carbohydrate per hour then for the third hour they stopped feeding and then they do a distance test so they're going as hard as they can for that for that final hour um and uh so and then the second study they there was no distance test it was just three hours of steady state running but they're feeding at uh one gram of carbohydrate per kilogram body mass okay so relative relative provisions rather than just a blanket 90 grams um and they uh yeah they're also feeding for the first two hours in that um and that they got a

lactose challenge in the third but i won't go in in the third hour but i won't go into that now unless you want me to no i think the carbohydrate feeding is the thing that most people correct yes absolutely and then the um the third one was uh three hours steady state running um and feeding for 90 grams per hour using um a beverage um and they were they were feeding for the whole but the whole three hours now when when they're doing this we're uh we're measuring their um their total body carbon fat oxidation and that's that's using a met cart so breath by breath analysis we put the mask on them periodically through the study um and and capture their their o2 and co2 data we are measuring uh we're measuring malabsorption of carbohydrate administered and that's done through hydrogen breath testing um and i can say a few words about that too if you yeah go ahead because a lot of people will be curious why why that is somehow uh indicate of or why that somehow indicates carbohydrate malabsorption okay so when we ingest some carbohydrate there are this look this can happen with all carbohydrate but particularly with fermentable carbs okay and uh the prime one in this case being fructose or fructose however you want to pronounce it that is that is by definition poorly absorbed in the small intestine so you know your intestine takes

takes takes it up but some of it passes through undigested into the large bowel where it ferments when it ferments your your gut bacteria release hydrogen and methane in the process but the gas we're really interested in is is hydrogen in this case that gas then diffuses through the through the gut lumen and into the blood and then we excrete it out of the lungs so when we do when we measure breath bags we're measuring parts per million of hydrogen produced and that's yeah coming coming out via that mechanism so that that tells us um tells us in you know there's a little bit of an indirect way as you can tell because you know it's got that pathway to go through but um it is a very good indication of in in a controlled lab situation for carbohydrate malabsorption perfect does that all make sense that's per yeah that's perfect because a lot of times when we just go out and spout out oh we're measuring this because it's poof it's an indicator of that if you very if you very simplistically describe as you did why that is then the case then people will go ahead and make the link okay it's just undigested fructose right under undigested carbohydrate that we're now then detecting in the breath correct correct yes so you've got these three groups you have these three studies that are going through a three-hour exercise test at a moderate intensity 60 of vo2 max yeah they're getting fed for ultra marathon runners yeah

which very typical training pace for for uh for ultra marathon runners and i would say typical race pace for some for some ultra marathon so very practical application you're feeding them carbohydrates that are at a high rate 90 or 70 was the other uh protocol 76 was the yeah that was the main of the one gram per kilogram body mass okay perfect so those are high rates of of of carbohydrate ingestion not the highest we've seen but certainly i would consider it on the high side still call it aggressive yes aggressive that's good especially in an ultra situation it's hard to keep that up over the course of hours and hours and hours oh absolutely absolutely um and um we're also looking at their blood glucose response so yeah every every 30 minutes we get them to stop for a few seconds do a finger prick check check their blood glucose uh what else are we doing oh yeah and and the other thing um that we're that we're doing periodically so every either 10 minutes or 15 minutes i think we found from the first study 10 minutes was too much um is uh checking the um what we we call the symptomology so we've got a questionnaire with a big range of questions where they rate their symptoms so you've got your upper gi symptoms um belching stomach bloating urge to regurgitate so worst case scenario vomiting um we don't normally have to ask that one funnily enough um if you've got the bucket in your hand then yeah they know um and

then yeah you've got your your lower gi symptoms um low down bloating um uh urge to defecate and and yeah if they actually need to stop to actually go to the toilet um and they rate all these things so five and above we call significant yeah you're thinking more about that symptom than you are about the exercise at that point 10 out of 10 obviously so severe you need to stop um and we also assess tolerance so tolerance to food and tolerance to drink and this is a really important one um um so yeah obviously if um yeah and uh and the question is actually um i can eat and you know i could drink so it's about force feeding essentially you know whether that be food um you know carbohydrate or water and we we assess that periodically through throughout so let's kind of dive into what the significant findings were and i'll let you take the lead on kind of what category of the things that you just mentioned you think are the most significant to initially talk about and what some of those practical applications are because i found i found a lot of different nuggets as i was kind of as i was moving through this and but i want to hear from you like when you guys are you're essentially uncovering information that was in previous studies that wasn't really analyzed or thought about in the same way

i look i look i remember seeing the original studies coming out and having something in the back of my mind going oh wow i wonder about this i wonder about that and this study kind of uncovers a lot of that so i want you to take take us through like as the research as the researcher the person who's who's analyzing this data what things were sticking out to you as the significant findings from looking at these three previous uh pieces of research and analyzing in a little bit of a different way okay okay you're gonna have to guide me through this a bit too jason because i'm gonna go off track and that's fine that's totally fine and and what what i did is sort of you know in preparation for this interview i sort of wrote down the key findings from from results because there's there's so much you know data in there but the way you've just posed that question makes me think should i even like talk you through that first i guess yeah um for a lot of people this 90 grams an hour if they're running is is a real problem yeah all right that's that's that that that was that was something that was really quite quite quite obvious to us in in in the very first gut study um and we you know and we're and because we're taking these multiple measures like you know across all these these um different things that that all relate they all come back to your ability to keep running at at your you know your your race pace um they they all give this sort of quite consistent picture that for so many people 90

grams an hour is just not appropriate let's put a pin in that really quick and kind of go back to the history of that right because i remember i remember when these recommendations were initially formulated and shout out to to somebody that you and i know quite well ask her jukendrup who pioneered a lot of this research and it was done and it was done largely through the mechanism of transport so you have glucose transporters and you have fructose transporters it turns out when you combine those two uh those two carbohydrates in in a specific ratio you can transport up to 50 percent more of them so going from the old recommendation of 60 grams per hour up to 90 grams per hour and i remember that being that recommendation being wholeheartedly adopted by the entirety of the endurance community almost instantaneously and it was kind of a weird phenomenon because it was initially based off of this transporter theory that had been researched right but it was as we were alluding to earlier largely like a i hate to to denigrate the some of the research that was done at the time but a lot of it was mechanistic in nature as we were alluding to earlier when we go into the practical realm and this is my realm i work with athletes on a day-to-day basis i was getting the same feedback that you are now finding in the lab that it's just simply not tolerable either after a certain duration or underneath certain conditions heat extreme stress hours after hours after hours the arduous conditions that you set your

lab up that you've kind of set your lab up to be and now we just we're kind of coming full full circle back to these original recommendations saying okay we need to make sure that they're couched in the right context when we're delivering this advice yeah yeah look absolutely absolutely um yeah and you know and also the you know the idea that uh you know the the body that the size of the person doesn't matter i mean right you know and to say oh there's there's this there was in that those make like and i i i wholeheartedly agree with you like i have so much respect for for the research that asca did and uncovering those mechanisms um but you know it's important to remember a lot of that work was done in um elite male cyclists um and you know i mean our elite male cyclists that they all sort of very closely within you know a certain you know height and weight you know it's not yeah yeah very homogenous group yeah um whereas you know in ultra marathon you know you might might have some some big guys that are you know 80 plus kilos if not more um and then you might have a a you know a 52 kilogram female and you know feeding them the same amount it just doesn't make sense does it but also the modality makes it less tolerance as well right just simply you know jostling up and down

in a running motion versus sitting on the bike is is absolutely and i don't i think this was underappreciated in the early 2000s when a lot of this was pioneered the modality seems to seems to matter a whole lot more than we had initially thought and this type of research is starting to uncover that where you know 90 grams or even 76 grams which you know should be relatively tolerable underneath some study conditions are now becoming quite intolerable underneath the conditions that you guys are asking these subjects to uh perform under yeah yeah yeah yeah absolutely absolutely um so yeah so that's the first thing these 90 grams of carbohydrate carbohydrate an hour might be too much for some individuals especially in an ultra marathon setting or especially in a in a rutting setting and that's showing up in both the hydrogen that you're measuring in the breath and in the subjective feedback or both yes correct correct so um in the in the hydrogen response um we had uh 38 percent of participants um showing a breath hydrogen response indicative of malabsorption that's a lot so yeah yeah um in terms of um yeah feeding tolerance as well so at the 90 grams for both studies so both studies you know slightly different protocols but they both showed the same thing um that the tolerance is is really

quite poor um is is do you attribute that since it is a little i'm not going to say a deviation but it is it is well it is it is a little bit of a deviation from what we would consider certainly a maximum tolerance what do you either from a practical perspective or from a research perspective do you attribute it to the mode or do you attribute it to some other mechanism as it being different as compared to what we've previously seen yeah jesse you absolutely nailed it before when you said with with the running and the jostling the mechanical rubbing all all that definitely plays into it you know we have no doubt um and you know and and that that's that's certainly in terms of um of um uh symptoms uh symptoms so gut symptoms you definitely get more symptoms um we do have some emerging data i'm not sure if i'm allowed to say this on air but we know in terms of gut damage it's a different story but i yeah like i say there's a little teaser for you is that what's coming out that's the next thing that's going to land in my inbox you know in a few months from now it's not going to bring you back on to talk about that one um but uh yeah look definitely the mode of running um that you know and and i mean because i mean i also as as a uh as the sports dietitian i work with a lot of triathletes you know and very often you know they're smashing it on the bike no problems getting it in and then all of a

sudden they get up and they start running and things just start to turn pear-shaped yeah and we think you know when you think about it this way when when someone feels uh you know really like uh you know crook in the guts for for want of a better term that you double over you're hunched over right very much like you're hunched over on the bike exactly and then when you get up it's like oh geez that's that's that's just hit me whereas with with your ultra marathon runners they're always in that position and they've got that constant um you know jolting and jarring well and we've seen this and you've seen this very particularly strategy play out in triathlon where you're you're feeding more on the bike as compared to the run to take advantage of some of the tolerability that we're now just seeing in the lab that's been used from a practical standpoint for i can't even tell you how long you know so it's one of those things where the research is kind of like lagging the athlete's actual experience where they can say listen i can do 90 grams an hour on the bike but on the run i'm going to go down to 50 just because i can't tolerate it so i'm going to take it over here and lose it over there and it ends up coming out in the wash yeah yeah yeah absolutely so that's the first big one is this we need to take a little bit of a different look at the tolerance specifically within running and we can't universally apply some of the 90 grams per hour de facto recommendations that have been delivered over the years we have to we definitely have to scrutinize that more as the mode changes yes okay yeah yeah so that's takeaway number one what else do you have what's the second one on your

takeaway list okay uh the fuel kinetics yeah did you yeah that's absolutely talk about that yeah this is another thing where once again i've seen this in our physiology lab all the time yeah but to see it actually kind of come out in the literature as well i'm like okay yeah i've seen this i know exactly where this is coming from yeah right okay so what what what are you what what have you seen then if you don't mind me asking you jason so the biggest thing is the rate of maximal fat oxidation where in a typical research design you're not going to see that get above like maybe 0.6 or 0.8 grams of of fat burned per minute but when we bring people into our lab for a commercial test we started out talking about commercial tests and we kind of we can kind of finish there i see all the time we'll have fat burners of one gram a minute 1.2 grams a minute and i have always attributed that to then you can tell me if i'm full of bs or not at this point i have always attributed that to they're coming into the test underneath different conditions some of them are coming in like perfectly fed some of them are not perfect they're these are real world world people it's not a study design where we can control every single aspect yeah we give them recommendations to come in underneath the same conditions but some people don't always follow that and so to see that actually like play out in a in a research design where we're starting to recognize that normally normally habitually macronutrient fed

normal macronutrient type of distribution athletes are actually seeing a little bit higher of a maximal uh maximal rates of fat oxidation as compared to what we thought earlier it kind of matches this commercial experience that we've seen all the time yeah uh yeah that's actually fantastic to hear you say that chase and i i didn't yeah i i probably yeah should have done my homework but i didn't realize you you will you will also do this sort of testing in uh yeah very very standard so just to give you a little bit of a background because we can kind of ping off of this so we use the united states olympic committee protocol so three minute incremental uh ramp test with a break between the threshold component and the vo2 max component and i'm not going to bore the listeners with what that protocol you know looks like but we're testing at different intensities i guess is what i'm saying but it's yes two separate tests separated by 10 minutes that tests both for the threshold component and for the vo2 max component and we're doing full gas analysis and lactate measurements either on the bike or kind of or on the run but my point with that is is when we look at when we look at the the metabolics of what's going on and what fuels are being oxidized we always see things that deviate from the literature because we're getting normal people in and under normal circumstances and in particular with the one that point that that kind of stuck out to me uh from your research paper was this slightly higher shift in maximal fat oxidation that you don't typically see in a lot of research

in a lot of research papers i've always seen that and we have kind of always seen that in the lab for whatever reason so let's go through that piece right there i don't know if that was on your list or not yeah no no that's that's fantastic and um yeah it's actually yeah really nice to hear that as yeah as i was saying before um because you know i mean sometimes i'm looking at the data i'm like trying to make sense of it you know i always doubt it myself um but yeah look and and and this is this is a big discussion point in in the paper that um the ultra marathon athletes they are regularly training at the point of stress glycogen this is this is what we think is is a big part of it so um one just just the sheer amount of time they're out running um and and stressing their glycogen stores and then backing that up constantly and um the other thing is um you know from from working as a sports dietitian it's very hard for a lot of uh athletes even recreational athletes to actually meet the carbohydrate requirements of the sport yeah and so you're very often going like doing sessions depleted or even just semi-depleted um and and that's what we think is is the reason why we see this you know and and in these more real real world scenarios where even if even if they have you know eaten uh you know a decent meal two hours prior even if you're feeding carbohydrate aggressively during the running um we still see these high rates of fat oxidation right um so yeah um exactly as you said

you know there's that that mean around the um you know 0.6 to 0.8 but we had um we had almost yeah almost half of our participants had a fat oxidation of uh of one or higher grams per minute yeah and that's that's a lot of fat burn right like 60 60 grams per hour like i i think of it this way right or wrong but uh you know if you're running for four hours that's that's like that's almost like a third of a tub of butter or margarine i love that analogy right there that's so brilliant i never thought about it like that that's that's great um so so when i when you see that right and you had the same discrepancy that i kind of had and once again we didn't plan this out like we're just practitioners and and you're in the research field and we just kind of noticed the same thing what do you attribute it to is this a training thing you mentioned that they're that they constantly stress their glycogen levels is this something where it's just a sheer byproduct of the volume and intensity that they're training at look i i think and and i guess we we as a lab yeah we think that it is about about the training that it's inherent in if if you're doing that sort of mileage that that your your ultra marathoners do um this is going this will be a byproduct of it so here let me ping you on this since you're since you also work with somebody since you also work in a sports dietitian uh perspective as well when i hear something like that the the alarm bells that go off in

my head are ultra marathon athletes are already good fat burners as a byproduct of their training a lot of them not all of them a lot of them okay very good thank you for that caveat a lot a lot of a lot of them are and so when we're undertaking training interventions that are intentionally designed to up regulate this thing that we're already good at those training interventions might be misguided for those groups of people there are all your caveats right there but that's how i handle it from a practitioner like like perspective and i'm wondering is there a way that an athlete an athlete just out there can get it can kind of get a fix on that or is that a correct way to look at it yeah look i i think so um yeah if you think about people going uh you know on extreme diets to try to up regulate this um you know that that that's good and fine but uh you know first of all yes as you said maybe you already are a really good fat burner um and and second of all there may be other flow-on effects that you're not aware of or we're not aware of and you know and i can come back to that a bit later if you like yeah um yeah uh i don't know does that is there let me ask you let me ask you this this way because you mentioned some people right yes can you tease out why some people are and why some people are not

um i think look yeah we when when we when we did we did this research we we captured their um they're they're like very very in a very crude way how much they're training right how many hours um but we're not we're not getting the detail you know we don't know how many years they've been training for or you know how often they do really long sessions and and how often they back them we don't have all that detail so um you know in our study where we've seen this massive variation um and i mean like there were a handful who actually really were not good fat burners you know um maybe they don't have the the years of training behind them or maybe so that there's that that factor something else we've observed is there are some people where we know they do the training like we we have the you know the full the full backstory we know they are a really high level ultra runner and doing that doing the case and yet they're just inherently really good carb burners and that's what they're good at and that's what their body does and they can perform really well doing that um yeah we we we do believe yeah so that you know we do believe there's a bit of a genetic component there um and yeah you know and in some cases uh yeah possibly even um a medical element so if someone

has some autoimmune disease that's an observation we've made i can't substantiate that from a research perspective but um it seems that uh well i mean we know when the body's under stress it favors carb metabolism yeah um so yeah that's that's yeah something we've seen but yeah i i we can other than that which is very broad as an answer yeah i don't think we can really pin that down why there is that massive variation i think we should back up just a little bit because the listeners are going to want to know like who are these people you're picking out competitive and elite marathoners and ultra marathoners all who have a mixed macronutrient diet and i think the carbohydrate percentage was 57 plus or minus yeah that's right yes yes so not a low carbohydrate diet i would consider that a normal carbohydrate carbohydrate diet that would be in line with issn's recommendation of 60 percent uh carbohydrate for uh for endurance athletes depending upon if you want to use a periodized carbohydrate approach or whatever but it's in the ballpark right certainly not ketogenic it's certainly not it's certainly not low carb and yet you're still seeing this wide range of maximal fat oxidation which is the peak of how much fat you're burning on a unit time basis um and we quite we don't quite know why like how to kind of like pinpoint that down and once again i i've mentioned the anecdote that

we've seen this in our physiology lab where this is great spread of people that are all the way down to 0.4.5 all the way to 1.2 i think i've seen some people that are like at 1.6 same setup they're in a mixed macronutrient diet they come into the lab and i've always attributed it to an inconsistent pre-test nutrition right they're coming in fasted for whatever reason it's first thing in the morning yeah okay there you go so we have differences we have differences there but then there also might be some other individual components that you could that you could test for as well let's go back to the discrepancy though right because this is another thing i wanted to talk about you don't see differences fed or non-fed in this maximal fat oxidation rate no no sorry i have to qualify that um um i guess what i'm saying there is even though they're fed with because in all our studies they're always fed we don't do fast but it's just not real world yeah so we think why why do that if it doesn't ever apply um so you know i mean sometimes we make dietary changes in our studies um you know because we want to actually like literally bring on some some uh gut damage yeah um and we know how to do that through through manipulating the you know the diet 24 hour or three day prior to the exercise protocol i get but but all yeah yeah but all our all our studies um yeah they are fed you know you know

they're two hours postprandial essentially i get it so you're saying you don't see it because of the way the research is initially set up where i'm i'm looking at it from we give them that recommendation you know we send out the standard lab packet and things like that sometimes they follow it and sometimes they come in they haven't read a single thing that's just real world people coming in for a test but anyway um we kind of get back to the study so it seems it seems to be though that there there still are some individual components at play because you have this standard you have a relatively homogenous group um as well as they are do they're all doing the same nutritional intervention right they're coming into the uh they're coming into the test bed and you're feeding them a standard amount on a per unit time basis you're still seeing this relatively big variance in maximal fat oxidation yes and we don't know what to attribute that to no no unfortunately not you know i mean yeah we're we're all just physiologically a little bit different that's true that's true okay so what were some of the other big takeaways that you could mention from uh from from analyzing all this data um okay so there's this uh there's this other concept that is frequently cited in um in the literature that um uh exogenous carbohydrate um oxidation but that the limiting factor is gut absorption does those words make any sense to anyone because it sounds ridiculous i've heard it a thousand times

i mean once you do your limiting factor is the gut i can sit here and i can recall i've probably got notes from conferences i've been to behind me that say exactly that i've probably seen a hundred slides with that as the title over the course of my coaching career yeah yeah and um you know and that that's frequently like as as you've just said that's that's so frequently quoted and and i would also suggest frequently misquoted or misinterpreted okay because when you stop and think about it well yeah what what you're eating you know the uptake's limited by the gut okay you know big deal well the the uptake and the metabolism i'm sorry yeah um but in in our study we we we couldn't determine that we we didn't it wasn't part of our methodology or or even what we're really interested in we're just because we're doing breath by breath analysis um and we didn't have any any traces or anything so we can't tell we can't tell exactly what's being metabolized when we do that analysis we just know it's this percentage of carb this percentage of fat um so we're looking that's that's why we always say in in the um in the manuscript it's it's whole body carbohydrate oxidation or whole body fat oxidation not coming from one specific source or another correct correct so some of it uh some of it's um coming straight out of the muscle and some of it's coming through the gut and you know from from the blood and and so forth but we we saw some uh some strange things that seem to sort of fly in the face

of of um of what the research has been saying all right and the research is saying when you've got really good carbohydrate availability um and i think i alluded to this earlier but when you've got really good carbohydrate availability that the body will favor carb metabolism now one thing we saw though was uh people start off at uh arresting blood glucose so you know it might be um you know 4.5 mini mole per per liter for you know for a good high level athlete with that's really insulin sensitive maybe just around the five and then they start the exercise and the blood glucose rises as you know it does partly from the actual exercise stress itself because the liver you kick kicks off um and and um releases uh glucose in the blood and then also you're feeding so you've got glucose coming through from from the uh intestinal lumen um now we we saw once that rises in the first 30 minutes the blood glucose stays quite consistently high across across most of our trials right or pretty pretty much across all the trials um and yet as even though that blood glucose is there one um your carbohydrate oxidation um but that starts to drop over time anyway even though the glucose is there in the blood um the the body's not

metabolizing that so where's the barrier you know it's already passed through the gut into the blood um you know the the barrier is perhaps um the the muscle itself like getting getting that glucose then from the blood into the muscle and then and then furthermore from the muscle being metabolized in in the mitochondria so um so that this is uh yeah this is sort of some of the mechanistic insight that that you know that we we think we got from from our data um whereby there can be different limit rate limiters for carbohydrate oxidation in different athletes and is it always tapering down meaning you start at a carbohydrate oxidation rate of you know what however many grams per minute and then it's tapering down over the course of one hour two hours three hours okay yes it always does but when we analyze the data and we're looking at statistical significance um for uh it was only one of our studies where it was statistically significant that that drop in carbox as but but in all the studies you see it you see it trending down like and and anytime you get someone in the lab and have them running for you know two hours or more you do see that um and you know you would be aware of that too right jason that you yeah you see the the respiratory quotient um yeah you see you see it drop which has always been an interesting phenomenon

because you know the carbohydrates on board right you know there's sufficient there's sufficient availability you also know that the exercise intensity isn't changing because it's a steady state exercise but yet still there is a metabolic shift over the course of time that is duration dependent from carbohydrate to fat for probably a host of very you know of of different mechanisms to where the body starts to favorably oxidize more fat versus carbohydrate as exercise goes along irrespective once again of the availability yes and this is this is where we think uh we we think you know and it's also you know like beyond this study and looking at the the uh the clinic stuff that we do um the actual caliber of the athlete we think plays a big part here oh really so i've yeah absolutely and and it fits in with um with an earlier study which was always cited as a gut training study even though there was no gut training protocol but they had one group of athletes where they gave them really high carbohydrate diet during intense like an intense training period and and the other one's not so high and um the increased carbohydrate oxidation rate seen in the high carb group was seen um as um as as the reason that yeah that they were oxidizing more carbohydrate i'm not getting too technical here i'll bring it back no no that's good so what what we see what we see in the lab get an olympian on the

treadmill and give them this same massive dose of carbohydrate yeah i called it aggressive before the 90 grams and they just take it up and as soon as it's in the blood bang it gets sucked into the muscle and you know and oxidized so even so you know this this olympic athlete the he he the uh you know we yeah we see the the blood glucose it barely got over like four and a half million million miles right even at 90 grams and yeah just smashing it on the treadmill and yet to these um these more recreational athletes uh it hangs around in the blood more before it gets taken up and that's even when they increase the intensity do you think that that's more that's a benefit of just their training because they're doing doing more high intensity training and then they have the kind of the the biochemical capabilities of transporting transporting transporting all that glucose into the muscle absolutely yes yes you know they're just yeah they're they're so well adapted at just taking up taking up carbohydrate and burning it so yeah well this is cool so you've got this piece of research right that challenged some of our previous notions on fueling particularly around the modality challenge some of the notions on the proportion of carbohydrate versus fat that could be burned especially when you're looking at it from a duration perspective give us give the listeners and give myself this is just totally selfish at this

point so i'll i'll totally the listeners will care but i'll care more what's coming down the pipeline like what questions are you trying to get answers to in the future and what do you think is like left what what do you think needs to be researched next okay uh yeah there's um oh jesus so much coming through mm-hmm if you want to take anything out afterwards i'll more than tell more be more than happy to take it out post-production but and then later i got oh i shouldn't have said that it's all good it's like you you'll have i'll tell you i'll tell you right now the listeners love this kind of back and forth you'll have three weeks between no wait two weeks between when we record this and when you can redact anything so go out i don't think we'll need to do that um i guess so what's coming through okay so we're we're very interested in um in gut microbiome yeah so you know and and that's something that's so heavily researched at the moment and i mean if you want to know my personal my personal opinion this is i'm not speaking on behalf of the university and this is my personal opinion i think so many people are getting a bit over excited about gut microbiome um and and in fact uh in our lab we're we're actually like sure we look at it and we try to analyze and try to make sense of it but it's such a complicated uh ecosystem inside the gut um so we're more interested in actually what's happened the changes in the blood

all right it's all very well saying this is you know x y z it's happening in the gut and you know short chain fatty acids and blah blah blah but actually what what's what's actually going through into the blood and what changes is that happening so looking more at the outcomes that's that's what that's what excites me on that side um yeah look what's yeah i mean my PhD where we're you know i'm looking at what is what's protective to the gut um but if we come back to the uh the ketogenic thing that you know we were talking about earlier um you know um and and you know this whole trying to upregulate fat oxidation that's all good and fine but something that hasn't actually been really looked at very extensively is um is that having other other health consequences that we don't know about um so there are some some theoretical concerns that that we have about that um and we actually have data which you know once again there's more data that i can mention but not tell you about but what are the theoretical ones i mean i think you should be a little ready to discuss that because the research always emanates from okay we have a thesis that this might be happening let's go ahead and investigate that thesis through this pro through this research design what what do you think initially might be going on okay so what what we do know is um high fat diets are very inflammatory like not just on the

body but also on the gut okay and you know i mean we even know we you know which which fatty acids have that effect in the gut and something else we know is um when you when you give people high fat meals um you increase um you increase um you increase the amount of gut permeability that happens so in in layman's terms you know they they call it leaky gut which you know we of course don't don't use that that term but the the the tight junctions in in the intestinal membrane actually open up and let more of the intestinal contents through and that's that's just normal physiology that's not illness or anything yeah that happens but the consequence of that is that some of the contents from inside your gut which is supposed to be external to the body even though it's inside the body it's outside the body some of that leaks into the blood and this this can cause uh you know your immune system deals with it it mops up but at some point that can become dangerous okay so if you um if you're on a ketogenic diet and then you put yourself through uh this incredible exertional stress like an ultra marathon runner throw into it some horrible hot conditions where um where the gut is under even more stress and um and getting more actual intestinal damage there is a potential for uh for things to go horribly wrong and i'm talking about um uh heat illness

um and and yeah i i guess it's it's not widely understood but but heat illness actually um is is is believed to originate in the gut and from gut damage and so um the one thing that we know categorically is that feeding with carbohydrate or protein for that matter but protein less tolerable but feeding with carbohydrate is protective to the gut so keep those carbs coming through particularly over the long duration and even more so in the heat that is very protective to the gut um and yeah i think that that's an area um in in the ketogenic side of things like it's great looking at uh you know fuel kinetics and you know performance outcomes and all that um but you know the broader health implications that's that's where i think more one needs to be done in that area i think the time is ripe for that because the initial investigations were all around fuel kinetics i mean going back to the old you know finney studies um and it it takes time to do the more nuanced hey what are the tertiary and second stream and third stream types of effects of these diets like they that you were just talking about but it that kind of thought process has always been interesting to me because we've always known some of the theoretical mechanistic underpinnings of why it might actually be true and we started out the podcast talking about mechanistic stuff in a joking way maybe we'll kind of end it talking about

mechanistic stuff in in this way i mean you do have to come back to it because it does make sense but then you have to investigate it to see if it's actually true or not right correct correct yeah absolutely that's fascinating that you guys are doing that i can't wait for so can i get you back on the podcast when that comes out or one of your colleagues yeah yeah well yeah you should yeah you should get one of my colleagues on yeah no that would be great i'm sorry don't don't misinterpret i'd love to come back on well we'll have you on any time like i said at the beginning man y'all are crushing it at monash university something in the water there is like putting out super volumes of studies that are all like really practical there um i appreciate your time and i appreciate what you uh kind of what you contribute to the space because it helps people like me vastly understand not only what's going on in the weird things in our lab every so often that we see that we were joking about but also ultimately how how to help athletes perform better and and so for me to you it's it's very important what you guys do yeah well thank you thank you very much and yeah thank you thanks for having me on i will uh i'll put a link to the paper that we referenced in the show notes but is there any other way that you want to mention to the listeners of how they can get a hold of you or learn more about the lab or the research that you guys are doing uh yeah i probably should have thought about this beforehand shouldn't i uh at this stage um yeah i mean i've heard your guests before and they say oh you know you can catch me on insta or twitter or whatever i'm terrible on socials currently i mean that hopefully that will change in

the future but um i'm happy to yeah if people email me i will uh yeah i will give an answer um and yeah with regard to um to monash yeah you can follow our um our facebook page so yeah maybe chasing afterwards we could yeah put on a link yep i'll have a link to everything in the show notes you're the second guest this week that has offered up their email address in the show notes and i don't know if i want to do that or not i don't know if i want to subject you to that because you'll be surprised that some of the people that reach out to you afterwards but you behave you're up to it more priority you man we'll get you out there in the space contact jason please and he'll he'll forward my detail as i was at no way you can filter through it i'm not filtering that man you start talking about diets i don't want to i don't want to step into it with 10 foot pole thanks again man i really appreciate this is super fun we're definitely going to have you back on when uh when this next bit of research comes out all right thank you very much jason all right folks there you have it there you go much thanks to chris for coming on the podcast today and i feel that like every month i'm going to have somebody from monash come on the podcast because they have absolutely been crushing it the research is all very high quality and like i said during the intro it just happens to have a little bit of an ultra marathon slant which i am very very very very grateful for i appreciate the heck out of each and every one of you listeners so much so that i

have just realized that very soon maybe on this podcast actually the KoopCast is going to reach 1 million downloads and when i very first started this podcast i didn't have any notion that it was going to actually get this popular and i'm incredibly grateful to the listeners out there and the support and the support that i've received from the community for this particular platform i talk about things that are not the sexiest they are not definitely not the most popular i don't bring on the most popular athletes week in and week out and try to specifically target number of downloads or number of listeners i just want to bring actionable information to the forefront and information that i will use in my coaching practice to the masses so thank you thank you thank you i'm going to do something special for the one millionth download i don't know what it's going to be yet if you have an idea send me a dm via twitter or via instagram i'd love to take in those ideas but needless to say i am incredibly appreciative grateful and humbled at all of the support if you want to support this podcast further give it a rating or a review on apple podcast that helps it reach a much broader audience as you guys know there are no sponsors or endorsements on this podcast and that quite frankly does limit the audience a little bit because i don't have partners pushing out my stuff which is totally fine for me but you can help

out by sharing it with your friends or giving it a rating or a review i'm very grateful for those that is it for today folks and as always we will see you out on the trails you