Continuous Glucose Monitors in Ultramarathon with Amy-Lee Bowler, PhD (c) | KoopCast Episode #190

trail and ultra runners what is going on what's happening welcome to another episode of the KoopCast as always i'm your humble host coach Jason Koop and this episode of the podcast is all about continuous glucose monitors in sport and specifically when the within the sport of ultra running and features amy lee bowler who is the author of a well-pinned review paper in the international journal of sports nutrition and exercise metabolism named the use of continuous glucose monitors in sport possible applications and considerations and in this podcast we discuss the history of cgms starting with their medical use within a diabetic population and moving to their potential use case in sport we also discuss the potential use for these monitors as a fuel gauge of sorts and their overall value proposition for their use where they can succeed and where they do indeed fail we also take a stab at the future use cases for cgms such as their potential ability to help predict low energy availability and relative energy deficiency in sport or red s as always this podcast is brought to you without sponsorship or endorsements of any kind and this is another great

use case of why i can bring on a guest who has a scientific perspective and a practitioner's lens to discuss a product that is out there in the marketplace and we can go over it all as it is all in an effort so that you the listeners can be more informed okay with that out of the way i am getting right out of the way here's my conversation with amy lee bowler all about cgms in sport all right we'll kick it off amy uh thanks for coming to the podcast today no worries good to be here um i'm i'm really excited about this um because i always like taking things whether they're devices or their training modalities or nutrition interventions or any training interventions that get really like popularized i like taking those and i like talking about them to the people that are kind of like behind the scenes because a lot of the times what happens is is they're able to scrutinize these things to a much greater degree than the lay public or even the athletes that are the that are athletes that are actually using them and with something that we're going to talk about which is uh cgms in sport it's it's something that you actually physically see on athletes so it's very much different than than what i would what i would consider a traditional nutrition intervention although this isn't specifically a nutrition intervention where it's in a bottle or in a

package and maybe somewhat like innocuously concealed into you know we always think about the special needs bottles in the marathon world we never quite know what's uh uh what's in them here we actually see it on athletes like physical person and it brings it to the forefront that much more so and i think uh instigates people's curiosity because of that very that very visual right there so i'm super excited to get to talk about that before we before we dive into the meat of it and so the listeners can get to know you a little bit better give the listeners a sense of like your background because this is a uh this is a trajectory that you're very much in the middle of right now and there seems to be kind of a constant theme emerging within your work yeah that's right so um i guess at the moment i'm still finishing up my PhD so interestingly uh when i first started my PhD we had this idea of looking at different tools that we could use to assess low energy availability and i guess we'll talk a little bit about that later on but we have this idea around well we know that there are some tools out there that we can use to assess low energy availability in athletes which is very topical at the moment um as this is real focus on i guess athlete health and well-being as well as performance and so we knew there was a number of tools out there that athletes or sports dietitians sorry used but we knew that there was some inherent inaccuracies with some of these tools and so we were thinking well

how can we better assess low energy availability in athletes with more accuracy and with more ease um and so that's kind of how my PhD started and interestingly we we started thinking about different tools that we might be able to use and around the time that i started my PhD we saw these companies coming out with these devices or cgm devices that were specific to sport uh and that was kind of around the same time we had this idea around cgms as well and so it was a bit of a coincidence and yeah it's been an interesting journey i think um as i've kind of gone through my PhD journey the interest in this field has just it's it's gone up exponentially and whether that's researchers or athletes or coaches or other members of the athlete support team everyone seems to have an interest in it and it's exactly like you mentioned because you can see it um everyone wants to know what is it telling what is it telling that athlete is it giving them any benefit should i have that on too uh and so i feel like and and you've seen it with i someone just showed me actually uh some athletes at the world open water championships swimmer was wearing it there that's that's the first time i've ever seen a swimmer wear one um and i know that there's been some rules and regulations around cycling where they've gone no one can wear them in racing so i think there's definitely a lot of interest and

interestingly my kind of research journey started in the carbohydrate space so i did an honors uh research paper on the ketogenic diet and athletes uh and i just kind of ended up on this journey along the carbohydrate energy kind of uh area and so yeah i guess it's been it's been a real journey i'm also a practicing sports dietitian myself as well so i i practice um and and um see the australian swimmers and skateboarders which is a really unique diverse mix of sports um and but it's great and it's it's kind of kept me in that real practitioner focused research rather than lab based and so my whole PhD has been centered around well how can we apply this research in the field and keep it really practical and applicable to practitioners that are working in the field so i guess that's kind of where my PhD has been a little bit unique um but yeah i've gone on this real journey uh with the cgms coming out and and that's kind of where my PhD has taken me and i think it's a journey that i've started and i feel like i can't finish it with my PhD finishing it'll probably be i'll be known as the cgm dietitian so i think that's kind of there's a lot more research to be done in this space and we'll discuss that uh later on but yeah well so for so first off um i can we're going to talk about it we're

going to talk about a paper that you're the lead author on the title of which is the use of continuous glucose monitors in sport possible applications and considerations and this is this is it it's an open access article in the international journal of sports nutrition exercise metabolism now that i've read that part because i certainly couldn't have memorized it i want to give you i want to give you like a large degree of kudos because when i first very when i very first read this i could read through both the PhD and the practitioner side of you because you're trying to merge both because you're trying to merge both of those and without even knowing a lot about your background it definitely came through so i would encourage the listeners if they're curious about what amy and i are about to talk about in more depth go and read the paper it's an easy read but more importantly it's a very practical read for people that are working with athletes or if you are a tinkerer which in the ultramarathon world we have a lot of tinkerers let's uh to put it mildly if you're a tinker and you're curious about this you will get a lot of uh insight into how you could potentially uh tinker yourself but let's set the table a little bit let's not try to go for the jugular quite yet um this is not the first time that a device that was originally intended for uh how how will i say this more of a medical use across a specific population has been adopted into the sport has been at least tried to be adopted into the sporting world there's a very rich history of this and we need to know we need to look no

further than the pneumatic compression boots that got popularized maybe seven or ten years ago that was a device that was originally intended for a different audience more of a medical audience that all of a sudden the athletic population looked at and said hey listen we could potentially use this for recovery and we're not going to talk about that but i think that that provides a good blueprint for what we see in the continuous glucose monitor space so will you give kind of a little bit of a brief history on that because i think that sets the table for where some of the applications might be and where they are currently not in the sporting world yeah certainly so yeah very similar to some of those other interventions that have been transferred over to the sporting world so cgms were historically a device that was used in individuals with diabetes and so these devices were used to monitor day-to-day fluctuations in blood glucose and so the reason for that is because in individuals with diabetes we know that they've got insulin resistance so the uptake of or i guess the uptake of the glucose from the blood into the cells there's a bit of an issue there and so using these devices allowed practitioners and individuals to monitor blood glucose and then to meticulously control the amount of insulin that they were dosing to reduce the amount of glucose that's sitting in the blood and so unlike the more traditional methods of uh analyzing or recording blood glucose cgms allowed uh individuals with diabetes

to see their glucose in real time so some of those more traditional methods like self-monitoring of blood glucose with a capillary uh sample so finger prick tests using a glucometer which they would typically do four times a day so when they wake up and then at each main meal or using venous blood samples so going and getting a blood test and and finding out your glucose that way which are obviously very invasive and difficult to um to obtain particularly if you're doing that every day um so unlike those more traditional methods of monitoring cgms are more of a consumer facing tool whereby individuals can um look at their blood glucose they can see periods of hyperglycemia so that's high blood blood glucose or hypoglycemia so that's low blood glucose and they can see that in real time and so then that provided an opportunity for those individuals who were living with diabetes to more promptly respond to some undesirable changes in glucose which may have occurred uh due to some dietary intake or perhaps some exercise that they'd done and so then they could dose their insulin accordingly to that um the cgm devices also allowed the health practitioners to adjust an individual's medication doses or prescribe some exercise regimes or perhaps more closely control the amount of carbohydrate a diabetic might have been consuming to then ensure that their glucose was uh controlled

within a certain range um and i guess we know that cgms have provided these individuals with more frequent accurate and reliable tracking of glucose which has then resulted in an overall reduction of their hba1c or their um their measure of glucose so um it has allowed a diabetic to have better control around their glucose and and and obviously gives them more accuracy around their insulin dosing so that's kind of where cgms have originated was really in that medical space use it in use with diabetes and somewhere along the line some and i don't know who to trace this back to and if you know please opine on it somewhere along the lines some clever athlete coach sports nutritionist said hey look at the look at that transition or look at that evolution that you had just described we go from an extremely invasive periodic period of having diabetic patients monitor their glucose four times a day it's a finger stick and things like that to a more frictionless environment that can provide readings across a 24-hour continuous period why can't we do this with athletes right that's the that's the switch that goes off in their mind and the promise is one of these holy grails of endurance sport which is fueling and there's no doubt across all of endurance sport you look at cycling triathlon running and you know we

have a specific ultra marathon audience here that one of the holy grails is to improve modify and i'll use the word optimize even though i don't i personally don't like that but it'll identify with a lot of listeners out there optimize fueling patterns somebody looked at this transition in the diabetic population said you know what we could get closer to optimizing fuel consumption and the way that people adapt to fuel consumption potentially use it using this tool before we get into that let's go through the cascade though because i think that's important for listeners to know before we start to talk about the utility of it and you started nodding your head for the people that are watching this on the youtube the youtube version so you know where i'm going with this how why is it let's go through the cascade and why it's important for for athletes to understand what happens in terms of what ultimately shows up as blood glucose from the time they ingest a food while they're exercising to when it's actually going to potentially show up on a monitor and then be functional from an athletic perspective yeah so to answer your question about who came up with this idea yeah i'm not 100 sure i i'm going to say i think it would likely be a cgm company um i know abbott uh is a cgm company and they have been kind of the pioneers in transferring this over to the sporting world um so they they have released a

sports specific device which is used by super sapiens which is a really popular company i'm sure some of the listeners would have heard of that company um not approved for use in australia or in the us actually uh but has been approved for use in in europe and some other countries um but that device is called a sports biosensor and so that device it's very similar to the device that's used in diabetics but it's kind of got a bit of a tighter range so it doesn't allow athletes to diagnose themselves with diabetes essentially but it allows them to track their glucose in real time and so um abbott has kind of yeah been the pioneers around that and i guess uh they are also looking to release a device in healthy individuals so that might be of interest for some of those listeners out there who like to tinker as you said um in some of those different devices but yeah i know that they're releasing a device for for individuals who um aren't particularly elite but you know might compete more recreationally um and so that that device is coming out for them in the near future but talking through that cascade of events um that occurs when someone eats something to then how it's reflected in a cgm so i guess we know that when people eat food containing carbohydrates the digestive system then breaks

that carbohydrate rich food down into sugar or glucose and so when when the body breaks back down it then enters the bloodstream so you've got blood sugar essentially and as blood sugar levels rise the pancreas then produces insulin which is a hormone that stimulates absorption of glucose into the cells and so you get this transfer of uh sugar from from uh the digestive system then through the blood and then um into the cells and so then that glucose is either used for energy if we're doing some exercise or some activities of daily living that require energy or it's then stored and so as the cells absorb the sugar from the blood the levels in the bloodstream then fall so we see this increase in blood blood sugar levels as uh the digestive system breaks those carbohydrates down and then once it goes into the cells then we see this drop in in blood glucose and so continuous glucose monitors work through a small sensor so it's about the size of two eyelashes and that's inserted into the interstitial fluid so it's not inserted into the into the blood it's inserted into the interstitial fluid and so the sensor measures interstitial glucose which is that fluid between the cells um and so then it estimates blood glucose through a reaction which is called the glucose oxidase reaction and there's some more

information on that uh in that paper that you mentioned but it estimates uh blood glucose from that interstitial glucose through this reaction now um something that's really important to mention here and something that's really important to be considerate of is that there is this 10 minute time lag between your blood glucose and the glucose that the cgm is reading in that interstitial fluid and that is essentially because the the glucose is going from the blood to the interstitial fluid and so you get this 10 minute time lag where you're waiting for that glucose to be shuffled in um so yeah so i guess that's just something to be considered considerate of there have been a number of studies that have validated cgms and have shown that it is reflective i think it's within about 10 percent of blood glucose but it's just important to know that when you are looking at this data in real time there is that kind of 10 minute time lag between when you see those results with blood glucose and when you see them with with the cgm data i'm really glad that you brought up that uh point because it becomes really important we talk about what the ultimate value proposition is here and to to not to oversimplify it but when we're talking about this in a sporting context and for the time being i'm going to leave out the health and wellness piece of this which i'm sure a lot of listeners are also familiar with and mainly through their the instagram ads that they get that they get pushed to uh every single day

but at least in a sporting context the fundamental value proposition here is to use it as a fuel gauge i'm going to look at a number on my smart watch or on my phone or i'm going to get notified somehow based on the reading of the interstitial glucose that is derived from the continuous glucose monitor and is going to tell me when to feed how potentially how much to feed potentially what to feed with and then on the other side of that how that feeding actually impacted this ultimate fuel gauge did it make a difference did i feed too much did i feed too little too little do i need to feed it more frequent doses with the different type of food stuff and things like that but ultimately the like i said the fundamental value proposition proposition here is is to use the numbers that are derived here to derive fueling strategies from it so you wrote the paper right there i know that's a gross kind of oversimplification of what we're doing here is that a realistic proposition at this at this stage of the game uh so the short answer to that question is that we just we just simply don't have enough evidence to support that kind of claim um i think it's a very bold claim and i think a lot of athletes have have heard of this as you said fueling gauge and gone oh perfect i've got something that can tell me exactly what to do exactly what to eat i'm definitely going to get one of those and i'm going

to put it on and i'm it's going to help me and i think it's it's a great idea but yeah there's just not enough evidence to support those claims at the moment so we know that and this was discussed in the paper but we know that there's been a relatively small number of studies that have been conducted and these have either been case studies so studies on one or two athletes or really small studies on endurance or ultra endurance athletes and these studies have largely reported glucose profiles of the athletes during a race so they've looked at that athlete during either a marathon or an ultra endurance race and they've reported on well what happens to their glucose during that race if we use a cgm to tell us about that and then some studies have then linked that to carbohydrate intakes so they've looked at well how much did the athlete consume during the race and was that reflected in their blood glucose as measured by the cgms now the studies that have been released i think there's been about five or six and there's been mixed findings so not all of the studies have said yep there's a definite link between carbohydrate intake and blood glucose profiles or glucose profiles measured by cgms with interstitial fluid and so it's really difficult for us to know whether these cgm devices are actually going to be useful because we just we just simply don't know some studies say yep there's a definite

link there and we can see that you know when an athlete consumes x amount of carbohydrate a high amount of carbohydrates their blood glucose shoots up when they don't consume carbohydrates they might drop into a hypo but not all studies show that and so i guess the the marketing of these devices as this personal nutrition coach if you like uh that acts as this fuel engage to tell athletes what they can do is largely based on the idea that cgms might be able to detect and then prevent some of these perturbations to blood glucose um during exercise uh and in response to intake of certain amounts of carbohydrate and so um it's it's a great idea and we in theory it makes sense but we just don't know at this point because yeah i mean i guess the marketing's been really enthusiastic and athletes have jumped on board uh but there's just not enough evidence for us to be able to to say yeah let's definitely run with this and use it and we know it's going to tell us what we want it to tell us we we just don't know your your description uh that you just went through that it seems like that it seems i'm gonna i'm gonna put a little bit of emphasis on this for you it seems very like a very simple proposition your blood glucose drops and then you ingest something and then your blood glucose rises that does seem like a very simple and effective value proposition

for anybody to jump on board with everybody can kind of understand that right most athletes understand that they need to take in some sort of fueling source in order to improve improve their performance part of it gets tied up in what that response is or is there an actual response and then the other part that you touch on a little bit uh that you touched on just a second ago is this personalization aspect is when is it biologically significant and when does the course correction become biologically significant because it's one thing to say okay you have this fuel gauge but like let's use the analogy of a car right i know my fuel tank is empty because it has a sensor in the gas tank that reads the level of the fuel very accurately that analog doesn't really exist within a continuous glucose monitor because all it's doing is telling you the rising or the rises and the falls of the interstitial of the interstitial glucose so i i hope that you can kind of expand upon this concept a little bit of the personalization or the course correction parts of this and why this is so seemingly simple but in practice actually tricky to create a real prescription from these numbers yeah 100 and so interestingly we've actually just conducted a study and we're about to submit this paper for review at looking at well what does an athlete's typical glucose look like when they're

under standardized uh dietary and exercise conditions and so for those who don't know what that means it just means when we when we give an athlete a certain diet and we give them a certain exercise session and they repeat that over a number of days what does their glucose look like without any of those additional interactions and so i think that's something that's really important to mention and and and as you said it is seemingly simple because we think okay you eat carbohydrate your body breaks it down into glucose it gets it goes into the blood your sugar goes up then it goes into the it gets shuttled out and then your glucose goes down and so that seems really simple but we know that particularly in athletes we know that there's this idea around metabolic flexibility and so particularly in endurance athletes we know that endurance training can promote lipid oxidation and so we know that they can favor fat for fuel and so then in this study that we've conducted we've kind of seen i guess a bit of evidence of that where uh there's this tighter control of glucose in this in this range um because the endurance athletes have this ability to favor fat over um over carbohydrate now in saying that though different energy and training demands are going to change the fuel that is selected and so

different training intensities different durations also different dietary intakes um different uh training status so whether you're well trained or you've only just started training or maybe you're a recreational athlete all of those ideas and concepts are going to influence your blood glucose and so that's they're all those different elements that then make this very complicated because you can't look at one individual and compare that to another individual and go oh we can make a direct comparison about what's going on either during training or during competition it's it's very much specific to that individual and then to add another layer of complication on top of that the study that we've just conducted we've then also seen differences between males and females and so um typically the females tended to run lower and we know that there's lower levels of some certain hormones that circulate during exercise and so they then cause females to run lower during these different types of exercise now again this study was done on some race walkers actually um and so that's one study that we've done in endurance athletes but then we also know that individuals who undertake high intensity exercise then might get this post-exercise hyperglycemia where they get this increase in blood glucose in response to high intensity training because you get this

real um release of of uh blood sugar and so it's it's very very complicated it it's yeah there's differences between males and females there's then differences between different types of athletes then your diet and exercise and your adaptation to the training all of these are kind of different layers that you've then got to put on top of that so that's where it's kind of like yeah these devices are great in theory and it might seem simple but then when you kind of i guess it's like an onion when you peel back the layers you're like wow okay i'm dealing with a lot here okay there's so much to unpack there amy and i hope i hope i hope people turn into the youtube version of this because we've got we've both got these shitting and grimmings on our faces with with all the caveats and onion layer peeling um i appreciate the fact that you that you use the term metabolic flexibility in air quotes um because that is something that absolutely gets thrown around in particular with what we are talking about but also in the ultramarathon world with what all the metabolic magicians out there that are trying to manipulate substrate oxidative oxidation primarily through dietary interventions they use the term metabolic flexibility in it well i guess in the way it was intended without an actual definition in one that does not have any uh uh end points that can be objectively identified which is problematic

because then it means everything so it can mean something to you and something to me and something to this athlete and something to an athlete but that aside i think that entire dialogue that you just went through really really illustrates when you're trying to simplify something as complex as fueling to a number there are a number of different things that can kind of go awry and once again using previous commercialized sports products as a little bit of a blueprint for this we have patterns of that heart rate variability is a great example everybody is very familiar with that you can't simply say well my heart rate variability is high and therefore things are good or my heart rate variability is low and therefore things are bad that's a very naive interpretation it's the same thing when you go into a different biological process and here it's interstitial glucose or blood glucose or blood glucose you can't simply say that it's high as this and low means that it high means this intervention and low means that intervention because there are all of these other things that get that that kind of get tied into it i want to use i want to use that as a little bit of a dovetail that will eventually maybe not initially but eventually get into another area of your expertise which you mentioned which is low energy availability or energy availability but one of the plausible um use cases for continuous glucose monitor is not just the fueling side that we went through which you just mentioned is incredibly complex but also using as a tool to get an athlete into a low carbohydrate availability state to induce very specific adaptations

during exercise while they are in that state and there's been numerous studies of this you can look at like two-a-day training and faster training and things like that where people are intentionally trying to induce this one of the use cases is potentially using a continuous glucose monitor simply to to more accurately define how long they are in that low carbohydrate state for and or the intensity that they are in that low carbohydrate state for and i mean i'm not going to put words in your mouth it seems to me that if we can't get the fueling right or if the fueling is complicated to get that this is even a further stretch to actually do but i want i want you to kind of like review how that actually might be a use case and can you see down the line at least once more research is done is this an application for it as well yeah i mean i think at the moment as i've said it's it's very difficult to determine whether cgms can simply tell us tell us tell us that i think um you know we're very much still in the very early stages of knowing well can it even tell us whether someone's feeling adequately firstly and then can we actually use it to to drive low carbohydrate interventions um i mean like as i've kind of mentioned already i think it's it's very simple in theory but once you kind of think more about it it's very it's very difficult and there's a lot of layers and so i think um the the idea around yeah like it's

it can tell us about low carbohydrate um intake and your blood glucose drops and we know that you go into periods of hypoglycemia and things like that and i guess low carbohydrate availability also kind of links in a bit with low energy availability but i i just don't think we're at that point yet where where we know whether it can tell us that that or not i think it's it we kind of need to get the basics right and know well can it even tell us about fueling adequacy first before we can then identify well can we use it to drive interventions um in practice yeah i mean i i look at those interventions this is me backing up from a coaching perspective uh you know several if not tens of several thousands of feet and saying with any of those types of interventions i understand that yeah two-day training you train in a fasted state however you ever want to induce that you're going to get some sort of a certain at least an acute specific adaptation for it that's fairly well demonstrated we don't know the cost and it's really hard to control in real time especially for real people who are professional athletes that have all these other kind of stressors going on and to your point i'd rather just get the training basics right and leave that adaptation on the table because it's probably really small and overwhelmed by all the other adaptations and the need to to to make it more granular or more precise with any type of tool continuous glucose monitor you can you know come up with a magic tool that could you know tell you that you're in that state i still

don't think i would actually take take the adaptation but okay so now let's get into like your your wheelhouse where you want to go with this because you've proposed and i know that you're and i know that you're working on research that could potentially use this tool to what i what i actually think would be the bigger holy grail in endurance training and that is to use it as some sort of precursor right to tell us in advance when somebody might be getting into a low energy availability state or some facet of reds or any constellation of functional non-functional overreaching however we actually want to put it i think that that's a bigger or i think that's at least not a bigger more impactful use use case in the fueling side of it and we don't have to get into why but this is an area that fascinates me to a great degree and i would like to see propagated in the future where does it stand right now in terms of how you could potentially use this to determine energy availability and what those applications actually are yeah so just going back to just what you said about the adaptations and measuring those like interestingly and i've spoken about this before uh you kind of you kind of go well is it worth do we need these cgms to tell us the adaptations that are occurring or i guess what an athlete's feeling or are we then just devaluing subjective assessments so an athlete might be able

to just tell you look i can feel that you know i'm i'm say for example when they're in a state of low carbohydrate availability when they're in that not necessarily adaptation that's occurred but when they're consuming less carbohydrate they're generally going to know so they're generally going to feel pretty shitty they're probably going to be tired there's going to be other uh more subjective assessments of of low carbohydrate availability or even low energy availability and so then we go well and it doesn't lag by 10 minutes let me throw that in there as well usually usually the time frame between when we see performance drop and or an athlete's subjective feeling of i'm bonking they might literally say that or they just say i feel like i'm low on energy typically that is very closely related to what's actually going on physiologically and then if you add a 10 minute delay to that you're actually making the problem worse right if you rely if you're over reliant on the number in that in that situation yeah that's right and i guess that's the problem with us saying you know this is a real-time measure because is it really um and some of those subjective assessments might be more of a real-time measure than than the cgm and so are we then just adding more numbers to a situation where we don't really need it um and so i guess this is where we need to be really careful and as you've mentioned so my my passion is in low energy availability and in the red space and so um something that we've kind of dabbled into

in the review paper is looking at well could these cgms tell us a little bit about low energy availability and even if we take the real-time issue aside where we've got that 10 minute lag a lot of the tools that we have to assess low energy availability at the moment you typically need someone to have been in low energy availability for a number of days or a number of weeks or even a number of years for things like bone mineral density and menstrual cycle dysfunction um those things need to manifest over over a longer period of time and so a lot of the time we can't pick up whether an athlete has been in low energy availability we can't pick it up early in the piece because we just don't have those tools to assess it and so i know i know you've had um eda on your on your podcast before and she has a really great paper um which talks about from the lab to the field so assessing low energy availability in the lab and then assessing it in the field and there's these inherent inaccuracies with assessing low energy availability in the field so we know that uh there's some some um issues with measuring dietary intake for example so we we know that typically athletes will either under or over report what they're eating um and i guess that's just that's just in part who we are as humans you know we like to impress the person that we're talking to and so a lot of the time people will give you what

you want to hear and so there's that issue with dietary intake and then we've also got issues with measuring training load as well so oftentimes that's not super accurate either um and then the other tools that we can use to measure low energy availability so things like dexa scans so we're looking at brain renal density um you know menstrual cycle dysfunction um bloods some of those aren't particularly useful either because either they're really difficult to obtain so we know that for dexa scans for example or for resting metabolic rate you need a well-trained technician you need to be on the same machine you need the individual to be fasted and rested and things like that and then for bloods we know they're a point in time assessment so they only give us an idea of whether that individual's in low energy availability at that one time so it's really difficult to measure them unless you're gonna have an athlete that's like a pin cushion and you're testing them every single day which i don't think they would like um we actually just ran a study where we've investigated the effects of low energy availability with the cgm and i'll talk a bit more about that but we ran that alongside looking at plasma glucose and capillary samples and i can tell you once the athlete had had every single finger pricked with a with a finger prick test and we've done every single side of both fingers yeah they weren't super happy so um so testing blood glucose and capillary samples all the time it's just not it's just not feasible and so as i mentioned earlier my PhD started with well we know that there's some

issues around these tools and my first paper actually was uh has been published and that talked about well what does sports statutes in australia typically use to assess low energy availability um and perhaps we can we can put a link to that paper up but um and that's where we kind of found that sports dietitians are typically using these tools that we know are inaccurate so they're using dietary intake and training load and menstrual function and um and we know it's really difficult to get accurate assessments with those and so that kind of gave us a bit of an idea to go well where what tools could we could we possibly use that might give us a bit more of an idea of a low energy availability in real time and that's where we came up with this idea of cgms and so historically um ann louts has got some really good work um early on she published this paper back in 2003 i think it was where she demonstrated this perturbation to blood glucose that occurs over a five-day period of exposure to low energy availability so what they did then was they tested venous glucose on day five um so after that five-day period of low energy availability and so on day five they knew that there was this decrease in blood glucose fasting blood glucose that is so um they used venous sampling because cgms kind of weren't wasn't so much hype around cgms back in 2003 but um uh so they proved this this uh i guess perturbation to glucose on day five now they didn't test in the four days um prior to that

they only tested on day five um so that's kind of where this idea around this perturbation to blood glucose in response to low energy availability came from and then there's another paper by um smith uh which looked at um uh energy deficits and they didn't call it low energy availability because it was only over a 48 hour period but they looked at energy deficit in military personnel and so we know that with the exercise regimes that military personnel conduct it's it's quite similar to athletes so you can draw a lot of a lot of similarities from that and so they put them into this very severe energy deficit so they were consuming about 250 kilocals per day so very very very low and they're expending about 4 000 um kilocals per day so they were starving um and so and what happened was after this 48 hour period they saw this increase in um hyperglycemic episodes so there was a lot more uh of the time spent in low blood glucose kind of what we would expect i guess yep um and and the interstitial glucose ran lower um and so that kind of i guess gave us this idea okay let's test what happens because we know that reductions in carbohydrate intake that might occur as part of low energy availability because usually alongside low energy availability you've got reduced carbohydrate availability and so that typically

we think would exhibit this downstream effect on on glucose metabolism and so the study that we've just conducted um unfortunately we didn't get a lot of participants we only had five and this is the limitation with a PhD is that you've got time constraints and you sort of got to get things done um but in this study we have actually seen this uh that acute exposure to low energy availability so we only did this over about 24 hours um it does perturb glycemic variability um but we did have a bit of a confounding factor around exercise so we can't kind of draw too many conclusions from that but i think we are starting to see some of this evidence that when an athlete is in low energy availability or or even a short period of energy deficit we do see these decreases in blood glucose now i think there's more research to be done in that space but this is kind of where we've decided to take it and i know uh there's a number of colleagues that i have uh one in new zealand one um uh near me at the sunshine coast in australia so they've all started phds looking specifically at low energy availability and cgm so i think there's some really really exciting research to come out in this space um in the future so yeah okay amy i'm gonna i'm gonna ask this question not for me but for the low carbohydrate in the fasting crowd that is listening to this that will throw eggs at me if i don't ask this

question how is that going to look different what you had just described we're monitoring continuous glucose and somebody that has low energy availability with these glucose perturbations and generally low glucose levels how is that going to look different in somebody who is truly on the edge of having lea or reds versus somebody who's just practicing intermittent fasting not that i'm advocating for that but that's what that that's what that crowd will certainly want to know and ask whenever this starts to come out like how should those actually look how should they present differently if we want to take a clinical turn on it yeah um i think that's a really important question um i think i unfortunately i don't think we know the answer to that yet i think um this is the whole idea between you know these within day energy deficits and then those extended periods of low energy availability and so when we first uh threw this idea around we thought well is it just going to simply run low or are we going to have this increase in variability or what what are we going to see in response to low energy availability and then another question then is um when an athlete then adapts to the low energy availability down the track do we then see their glucose jump back up to normal levels because they've adapted in this starvation mode um and unfortunately i don't think we know

the answer to that but i definitely think it's something that we've thought about because we're like well what how does it look different how do we know whether an athlete is simply just in a in a like you said intermittent fast or an energy short-term energy deficit or and then what's the difference between that and then someone who's in low energy availability and i think that's one thing that's really important to remember and to mention is that i don't think these tools could ever be used as as a one-off tool with nothing else so i don't think we can ever then forget okay we're not going to measure dietary intake anymore no need for training data you know we can just use a cgm i don't think that's ever going to be the case i think we're always going to need cgms to be used in conjunction with other tools to then paint that picture for us to then go okay maybe this athlete has only been in you know an intentional energy deficit for this one day because we want to get those adaptations some low carbohydrate availability or we can clearly see that there's this mismatch in energy intake and energy expenditure over this extended period and so we then know that okay perhaps this athlete is getting into that you know lea danger space and so i think that's something that that's probably important to remember there is that i don't think this device will ever be able to be used on its own um it's something that will have to be used in conjunction with other tools to paint that picture to tell us about about

those differences similar to the heart rate variability analogy i i said earlier you can't just say high is good and low is bad no you have to put it into i mean now that i'm thinking about it heart rate i've been coaching for long enough that that we used to use heart rate just resting heart rate morning resting heart rate as a marker or as the marker of over training and since then we've learned you know what we need to take this into consideration with all these other things if we really want to get a good fix on it so your your point that we can't use it in isolation for much of anything is uh is is really well taken um let's let's go back to the fundamental fuel gauge value proposition i think this is a good way to uh to wrap this up so we kind of mentioned we don't really know right now right we don't know what's material what's biologically significant how do we set like normalized ranges wave your magic wand you can be queen of the world for you know the next 20 minutes or something like that and just conjure up anything what would that look like like if it were a perfect scenario if we were to use this as it's specifically within the fuel gauge piece of it what would need to happen either from a research perspective and or a hardware and software perspective for that to actually come to light because i think that that presenting the idealistic situation is helpful for people to understand where these where these gaps actually are so if they do want to tinker around them they

know where their blind spots are so if you were to say hey listen i'm going to do this and this is going to be perfect what would that actually look like and you can be as theoretical and whimsical as you want to in this um it's definitely something i've thought about but unfortunately i'm not an it whiz so i can't develop just make it up um so i think if we were to in an ideal world if we were to use these devices with athletes i think there needs to be some additional technology around around these these devices so i think at the moment if we if we take super sapiens for example we've got the cgm device we've got this app where you can um sync to your sensor via bluetooth your data syncs automatically it appears on the screen you can see your blood glucose in real time but i inverted commas again um and you can then add in say if you've eaten 50 grams of carbohydrates so if you ate like two bananas and you put that in your app and you go okay this is where i've eaten 50 grams of carbohydrates i can see this what happened with my blood glucose um and and i know that there's some some been some adaptations around that where you can you know you can see your blood glucose on your power me on your bike and all those kind of things but i think what really needs to happen is this real integration between um dietary intake recording

software so things like easy diet diary my fitness pal those those kind of things where people can put in their exact dietary intake with carbohydrates protein fat um we we've got an idea of the gi of the food so we know whether it's simple sugars or more complex sugars and how it's being absorbed um so we've got this integration between blood glucose we've got dietary intake data and then we've got some kind of estimate of training load data um and and i think all of those things need to be layered over the top of each other for us to get a really good um idea of what's going on and to to provide that context and and something that i've really struggled with um over the past few years while i've been doing this is been when you present this data back to an athlete when you look at the data that say abbott produces where you get this graph of your blood glucose and you've got these little dots to say this is where you ate carbohydrate it doesn't really tell you a whole lot so you're showing it to the athlete and they're going oh yeah like that's sweet whatever like but they don't really know what it means and so you really have to then uh manipulate the data to show them okay this is where your blood glucose is sitting these are the periods where you've eaten x amount of carbohydrate or x amount of energy these are the this is what you've expended on that day and so then what is your blood glucose doing in response to

that and so then then you can get this picture across you know three five days two weeks whatever period you choose to monitor for you can see okay well on this day you haven't consumed you know you haven't matched your energy intake to your energy expenditure and this is what's happened to your blood glucose or you might look at it and go okay on this day you didn't match your energy intake and your energy expenditure your blood glucose has still been okay but then on the next day when you wake up in the morning we can see that you've dropped really low here and then you've trained and you've eaten whatever and then we see this response and so i think ideally there needs to be this i guess consideration of the the athlete and the consumer and there needs to be this real practical way of analyzing the data where the athlete can make more sense of it because at the moment there's just not that ability to but for the cgm to spit out that data and the athlete or the practitioner uh to take that data and then go okay we can actually make sense of that there's a lot of work that needs to go into it to then produce this kind of readable graph where an athlete can see exactly what's going on and i think that's something else that that's that's really uh at the moment is something that we really need to take into consideration is that i don't think we're really at that stage where athletes can run away with these devices and just go and do their own thing

and i think that's a real dangerous area to get into because uh you know we we just don't know what the devices are telling us you know we have a bit of an idea but it it's really difficult for an athlete to run away and go oh okay my my glucose has dropped low here so i need to go and eat you know a bag of walley's to like try and get my glucose up and and and oftentimes it might not even be that your blood glucose has dropped low so we have seen um in the past that sometimes the device can just become dislodged and so because it's become dislodged your glucose is reading low and so it's not actually a true low but then the athletes panicked and gone oh no i need to do something about it and so i think at the at the moment it's something that really needs to be used in conjunction with a practitioner and we just we just need more development around that and and i guess i'm a real advocate i guess as i said for the athlete and for practitioner facing tools because i'm a practitioner myself and i want to see practitioners and athletes be able to use this device in a in a really easy way that they can make sense of um and i just don't think we're at that stage yet it's yeah it's very difficult to take the resources that we have at the moment and then and then run with that and give feedback from that because it's just not at that stage where we need it to be amy the so that whole dialogue is spoken like a practitioner who has had people come into her office with a bunch of data or a bunch of

output i'll put it that way a bunch of output and go and and asked you what i do with this and you go but i don't know i mean once again i've seen it a hundred different times with a hundred different things but i it definitely resonates for me here here's what i'll add to this we'll give the answer away and then somebody can either either rip our ideas off or you and i can go into business and we can sell these to you know the whole athletic population i think if you can tie the intervention to the outcome both short term and long term and then machine learn that over months and years to to determine what interventions produced what outcomes with a specific individual that's that that's the that that's the functional use case for it so this happened i then did this it produced this biological response within the blood glucose that we can accurately accurately measure and things like that it made this type of performance improvement and or created this chronic adaptation that we think has an impact on long-term performance let's continue to do that from a training perspective and see how that changes the biological response i think that that dialogue versus i'm low taking a bag of gummies i'm high i don't need to take in a bag of gummies that kind of like the fuel gauge piece right and i'm now remembering that a lot of times in the automotive world when you have these analog gauges they call them dummy gauges right they're either green yellow or red and i think that that's very i think that's

analogous here to where we're trying to oversimplify a complex biological process that has many different outcomes to take something in don't take something in or reduce what you're taking in right those three kind of those three kind of levels i think that kind of does a disservice to ultimately what we're doing because we're concerned about performance and acute and chronic adaptation at the end of the day and there's currently that's the big hole right you're just looking at the acute biological response but there's nothing to tell you what the long-term adaptations are to the intervention that you're actually doing that's the holy grail for everything from a coaching perspective i apply an intervention what's the long-term adaptation from it if we can find that out yeah whatever means i'm i'm game for it yeah no i definitely agree and i think that's the difference between using this device with individuals with diabetes and using it with athletes there's a there's a whole different goal and a whole different idea in mind as to why you're using it and what you want to get out of it and i definitely think that's yeah it's something that we need to think more about and and just use it more and and get more research on it and just you know get people out there who are keen to use it and using it with more athletes and recording that data and just really getting a sense of what what exactly is it telling us because it yeah we just need more of that practical um evidence and and use in the field to know how valuable it can be i'm hopeful i don't know if you're expressed that same hope that i do

but i do realize that we've got a long way to go before there's anything sort of practical right now and as with a lot of things the use cases tend to get ahead of the or the the theoretical use cases tend to get ahead of the actual use cases and i think this is a great example of it that we start to see in in practice across a whole lot of athletes yeah definitely yeah i agree this was awesome amy i'm going to bring you back on the podcast when you come out with the next paper that you're working on because we're always concerned about low energy availability stuff with athletes particularly an ultra marathon audience where we're expending a lot of calories and it's hard to keep on top of that very high volume training groups and you combine that with there's a section of our uh uh just of our whole population within the ultra marathon world that is very low carbohydrate curious you know for lack of a better word and that can be a very toxic mix and anything that we can do to understand the low energy availability sphere serves us very well in terms of how can we determine when it's deleterious and what sorts of conditions with what sorts of people what are the long-term consequences so i'm going to pigeonhole you right now and bring you back on the podcast when whatever that's out because that'll that'll certainly be a fun one until then though i'm going to leave links in the show notes to all the papers that we talked about where any other resources where they can learn more about you your work or any of the tangents that we went off on

uh yeah so i guess um if you want to know more about me um i am currently doing my PhD at bond university so uh you can find all of my research pieces um on the bond university website um also my colleagues um dr greg cots who's my supervisor um dr vernon coffee and professor louise burke um we're all really interested in in this space and so we're trying i guess to get more uh information out there and so um hoping to continue talking about this at a number of conferences um and things like that um so yeah just yeah keep an eye out i guess um hoping to publish another paper in that same journal where the review paper is published very soon so yeah just keep your eyes peeled um and and as i mentioned there's a number of other different researchers that are definitely interested in this space so um i definitely keep an eye out for more research to come out in the near future awesome amy thank you thank you for what you do first and foremost because it definitely informs us in the sporting world to a tremendous degree and particularly when you can blend the academic and the practitioner side i think it brings a very real face to a lot of the egghead stuff that is very difficult to weed through at the time so i'm always appreciated appreciative of the people who can make that that translation yeah definitely

all right folks there you have it there you go much thanks to amy for coming on the podcast today and lending us both her scientific perspective as well as her practitioner's perspective on how we could potentially use cgms and sports and where some of the blind spots currently are within their use i found this conversation absolutely fascinating because i know each and every week i get questions from you guys the audience out there on is this a valuable tool to actually use y'all go and check her paper out is extremely easy to read it's an open access paper you can get it for free and for the coaches out there in particular i do think that you guys will get a great amount of information that you will be able to use the very next day right after reading the paper from reading her uh from from reading her review that is linked up in the show notes each and every week this podcast come to you comes to you without any sort of endorsements or sponsorships and i know that is unique in the podcast world and it's something that i harp on each and every week what you also should know is that this podcast is not free it cost me personally about a grand a month to produce it i pull it out of my pocket and i set that money aside and it is a joy to actually do so and i consider it an honor to do so but it is not free i do get a lot out of it professionally it's a great marketing arm as well as it's a great professional arm i have been able to expand my professional

network far greater than i would have ever anticipated when i very first started this podcast however i always get asked how can i actually support this podcast i can't buy any of the products on it you don't have anything for sale that's directly to the podcast there's no patreon page or anything like that well here's your answer you can subscribe to my new research newsletter research essentials for ultra running it comes out every single month and the research team and i we review three papers in incredible depth that are specific to the ultra marathon world and just this month just a few days ago in fact we released the latest issue and one of the pieces of research that we looked at just happened to look at ketones and their effects on cognitive function in an ultra marathon really fascinating paper i think you guys will find it fascinating as well because this is something that is also all of the rage so if you want to support this podcast check out the link in the show notes to research for essentials for ultra running it's only 10 bucks a month and the depth and expertise that you get out of it is absolutely incredible you won't be disappointed all right folks that is it for today and as always we will see you out on the trails