Episode 117 Transcript – Training The Gut For Endurance Athletes


Hello and welcome to the Ideal Nutrition podcast. My name is Aidan Muir and I’m here with my co -host Lea Heigl and this is episode 117 where we are going to be talking about training the gut for endurance athletes. And I’m pretty sure the last podcast we did that was endurance related was carb loading. I remember saying in the intro that I didn’t really have any interest in that even though it’s something that I obviously care about work with a lot of athletes, but I didn’t really have any personal interest in that. But since then, I have done a half marathon. So I have a bit of personal experience in this space now.

I largely did that to get a bit of an interest in this kind of stuff because I don’t, I care a lot more about stuff that I have personal experience in that I have interest in because of that personal experience. And there is a few things here and there. Like for example, I care about like PCOS, even though I can’t relate to it. There’s obviously other stuff outside of that, but I often do find if it’s something that I can have personal experience in that does help.

And that kind of leads into this topic where we are talking about training the gut in relation to before doing that. Like obviously I had occasionally tried gels and stuff like that, but there’s nothing really like trying gels while also trying to run as fast as you can at the same time for a long distance. So it’s cool to kind of play around with that and get some personal experience there too.


Going into this topic, I want to talk firstly about why it matters in regards to training the gut for endurance athletes. I think I should touch on the fact that I have never done an endurance sport in my life. So unlike you, I don’t have a vested interest or personal experience, but I have worked with many endurance athletes in my time. And I think it is a very beneficial thing in terms of training the gut. So let’s talk through it.

We know that carbs are the best fuel source for higher intensity endurance activities. It is going to be that fuel source that our body uses very efficiently and maintains good performance. The best endurance athletes in the world are typically consuming over or around 90 grams of carbs per hour. That is quite a lot. And that is during exercise, during their training.

It is almost guaranteed that if you went to 90 grams of carbs per hour straight out of the gate, if that’s like, you’re like, yep, I’m going to do 90 grams of carbs per hour. I’ve never done any intra -training nutrition in my life. Then you probably will have some gastrointestinal side effects. Like you’re probably not going to feel awesome on like the really extreme end. Maybe that’s like runner’s diarrhea or, or like really bad side effects on the lower end. Maybe it’s like just some just general discomfort, but it’s going to be unlikely that you’re going to be able to tolerate such a high amount straight out of the gate, straight off the bat without training your gut to do that. Cause it is not something that a lot of us inherently have the ability to do.

And just a quick note on that 90 gram of carb portion is it is not just glucose in isolation. It is actually a mix of both glucose and fructose that that recommendation is based around. Glucose alone is probably, you’re probably going to tap out around 60 grams per hour mark before you just get general symptoms from having too much glucose and that not being able to be all absorbed, et cetera. So yeah, that 90 gram of carb model is a mix of both fructose and glucose. So just something to mention there.


Yeah, it’s just because they have different like ways that they can be absorbed. So by adding multiple forms, you can go above that 60 gram kind of limit. For context as to what that would look like, most energy gels, like say your Enduro energy gels, are around the 21 to 25 grams of carbohydrate per gel kind of mark. So if we’re looking at, say, let’s go on the bottom end of that, let’s say 20 -ish grams, like how many gels are we talking to get up to that? Like we’re getting near the five gels, it’s just like the four gels per hour kind of mark. And that’s actually quite a high amount.

Like if you speak to like recreational runners who run a bit, but they’re just taking gels. it’s rare for people to go anywhere near that high. And one of the reasons why I’m so big on telling people that 90 gram kind of number is it gives people something to kind of strive for. If I just say have as many gels as you can without it being detrimental or without it leading to issues, most people do stop at say like two gels per hour.

If I say, there’s people out there having 90 grams of carbs per hour, people shoot for that. And we do also have some evidence that going higher in some cases might be beneficial. Like there’s at least one study on trail runners where they found that 118 grams of carbs per hour outperformed 90 grams of carbs per hour. But that’s a much more debated topic because it seems like physiologically the most we can really be metabolizing is about 90 grams per hour. And it’s kind of controversial whether going above that is beneficial.

But there is evidence that also people doing the Tour de France are going above that mark as well. I just like to set a number, let’s say 90 grams, because it seems to be what, it’s not really controversial that we can get up to that with training the gut and everything like that too.


Most people are capable of it at least after training the gut a little bit.


Yeah, and I suppose I should say that there will be people who definitely can’t get up to that even with training. Everybody can improve what they’re capable of taking on. Not everyone will be able to get up to 90 grams, but everybody can definitely improve what they can take on.

Going through mechanisms of how does training the gut or practicing this actually translate to being able to take on more without having symptoms. There are a few mechanisms. One kind of vague one is just simply reduce feelings of fullness if the body gets used to doing this. Think of it being like if you always exercise without ever taking anything on.

It’s kind of like, I know it’s a bro science thing, but it’s like your body kind of breaks out when you have some food like coming in while exercising for the first time. And it’s almost like your body just gets more used to that. This is relevant for both fluid and for carbohydrates. A less bro sciency one is improved carbohydrate absorption and oxidization. These things improve when you actually practice them and try them. The intestines literally increase the amount of glucose transporters if they are exposed to carbohydrates more while exercising.

And that is really useful. It is also one of the reasons why we can’t do, you can’t just go low carb all the time and then for an important event, start trying to take on carbs because you’re less likely to be able to metabolize higher levels of carbohydrate while doing that. That’s why training the gut is quite important.

And then another interesting one is improved carbohydrate specific gastric emptying. So the amount of time it takes the carbohydrate to like go through the stomach and go to the next level of digestion. Tthat literally does speed up. And it is carbohydrate specific being like if you had trained disability, but you hadn’t trained your ability to digest fat, for example, specifically, and you ate a food that was a combination of these things, you would see quicker carbohydrate specific gastropuntin because of that.

So I don’t really think the mechanisms matter that much. I do think the outcome is what matters more and getting better at it. But it is useful to know even literally that increase in glucose transporters that there are physical things that are occurring. It’s not just placebo, your body literally does get better at doing this.


Let’s talk a bit of strategy now. So if you’re someone who is starting out with training their gut and trying to get up to that 90 gram per hour mark, like where do you even start? So, I mean, I would typically start around that kind of 20 to 30 grams of carbs per hour mark. I think most people can tolerate that at a baseline. Some people can’t have definitely come across clients who are like, we start at such a bare minimum. But look, I think most people can get to that 20, 30 gram of carbs per hour mark.

So even like looking at a gel an hour. So starting there and literally building that up with each session or every few sessions or whatever your kind of tolerance is and how that improves over time. Everyone to get as different in terms of how quickly that happens. But literally just kind of adding to that number until you get to where you want to be for optimal performance.

I guess I’d also say that you’d probably want to start doing this in sessions that are a little bit lighter in regards to intensity. It’s going to be harder to digest these foods when you are doing higher intensity work. So a good place to start is low intensity stuff. So you’re literally starting at a low amount of carbohydrates per hour in low intensity sessions one to two times per week and building from there.


Yeah. I’m really big on making sure that everyone has a positive experience with that. Cause like you’re really trying to get it so that eventually you could use this on race day and stuff like that if racing was your goal. But a hundred percent start with lower intensities just to build a positive experience and be like, this went well, let’s try something a little bit more aggressive the next time, even in terms of slightly more carbs or at a slightly quicker pace or anything like that.


Yeah, as soon as you’ve had a bad experience, I feel like you can even just nocebo yourself into a bad reaction every time. And I definitely have had clients like that.


Yeah. That’s why I really am a big fan of starting super low.

The next one is kind of talking through alternative options. Because say somebody does have issues with say like 20 grand of cars per hour. I obviously one thing we can do is we can go lower. Like there’s always a super low amount that everybody can tolerate. But another thing is it’s like, what if that specific option just happened to be a trigger for them. Like what if, for example, FODMAPs and stuff like that, what if it was a FODMAP related issue?

The first simple step is trying different gels. A lot of people have success literally just by switching to another gel. Maybe it’s got a different ratio of fructose to glucose. Maybe there’s a whole bunch of explanations, but switching gels is a common theme that I’ve seen people have success with. You can also try different combinations of fluids and gels. Like what if instead of gels you’re having like Gatorade or something like that. Or like some people will find that liquids would be better than gels or vice versa for them personally.

Another thing that is, it’s on the package but I don’t know how well like well practiced this is but gels are designed to be consumed alongside water as well. Typically the standard gels are designed to be consumed alongside around 250 ml of water. If you’re going out for a run just by yourself, like you don’t have any, like there’s plenty of situations where you wouldn’t do that. I personally am completely fine just having gels by themselves with no water, no issues, never ran into issues, but if you were running into issues and you weren’t having alongside water, the first step would be to do that because that would dilute it a little bit. And it can often be tolerated a bit better if it is done that way.

Another thing I’ve seen heaps amongst the running community is people doing different frequencies. If I have a gel and I think most people do this, you just real quickly just have it by itself, like one mouthful and you’re done kind of vibes. But I’ve seen other people spread it out over longer periods of time and some people have success with that. Other people don’t have success with that. But if you were running into issues, you can just trial both and see what works more easily for you.

I personally think that having it all at once means if you do feel anything, like it doesn’t sit super well, it probably just shortens the duration. Whereas like if you spread it out, you’re running the risk of having that feeling for a longer period of time. But alternatively, you can see that it’s less of a hit all at once. So spreading it out could be another option.

Another one is simply consuming less carbs. Like if you’re struggling to build up, like as we said, like not everybody’s going to get to that 90 grams of carbs per hour. The goal is just to find what is that sweet spot where it’s as high as I can get it to so that I can maximize the amount of glucose slash glycogen I have, which is our best fuel source for this activity without getting detriments that outweigh that benefit. And if you keep trying to build up,and you keep running into issues, you can just have slightly less, that’s okay. You’re just trying to optimize things for you personally.

And then the final thing, which I kind of touched on already is like considering other things that could be contributing to GI upset, such as FODMAPs. A guy named Ricardo Costa, he’s a researcher. I don’t know him personally, but I’ve seen his research where he’s also a Dietitian as well. He’s done a few things like if you go low FODMAP for a few days leading up to an event, you’re less likely to get runner’s gut during that event. So if you’re somebody who found yourself always running into runners gut and that was a factor that was an issue when combined with trying to have these carbs during the event, you could try going low FODMAP for a few days thing up and see if it helps. It might help, it might not help, but it’s another option as well.


I think the last thing I also want to note is also just around the kinds of foods that you are using. I have a lot of clients who. wanting to start with training their gut, wanting to start with intra -training stuff. And they’re like, I want to do whole foods. I want to do dates and all this other stuff. If you’re just starting out, it probably is best to use something that is a little bit easier to digest that has a minimal fiber content, a little bit lower food volume. So I think like we talked a lot in this episode about gels and fluids, like your Gatorade and other sports drink and even things like your chews, like your cliff blocks. I think that is a great place to start rather than whole foods.


Yeah. Talking about that even more like another thing, this is a separate topic, but I’ve seen a lot of people talk about how like they were running into gut issues when they were using gels and when they switched to whole foods, they were no longer running into that. And I think a large percentage of time when that does happen, people have simply reduced their total carbohydrate intake because they’re eating similar amounts of food volume, maybe slightly more, but to get that through whole foods often works out to be a really large food volume in comparison.


100%. Definitely have seen that quite a few times.

All right, so a little bit of a summary for this episode. So in terms of carbohydrates during your training, during races, et cetera, the big reason why you want to optimize this and get to ideally that 90 gram of carbs per hour mark or something along those lines is so that you do have that carbohydrate availability during endurance training, endurance events where we have very limited glycogen storage that we can pull from. Once that is gone, we do kind of want to top up to maintain optimal performance.

But straight out the gate, not a lot of us can get to really high amounts of carbs per hour. So training the gut, starting small and starting slow and building your tolerance over time is the absolute best way to do that.


Yeah, for sure. I might even share like my two cents on my experience with that. I was very blessed in that the first time I went out, practiced what I preach, I was like, I’m just going to start at 30 grams. Had a good experience. Yeah. I was like, I’m going to double that next time. Doubled it. 60 grams. Had a good experience.


I have clients that have done that super fast and like literally no issues. No issues, yeah. And others that will take a couple of months.


Yeah. In like by session four, I tried 90g because I’m just, I’m just going to see what I can do. And like I felt it, but like it was, it was a good experience as well. One thing that I didn’t trial in training was sending it at race pace while having that 90 grams of carbs per hour. And because I didn’t try it during training, when I got into like the actual half marathon day, I would have had like 67 grams of carbs per hour while doing it race pace. Cause I’m just like, I’m not going to mess with this. I’m like, I just want a good diet. I’m just going to go a little bit lower than that. That’s probably more than like most people are doing anyway.

But it was interesting just being like, this came quite easily to me. But it’s also one of the reasons why I’m like personal experience is great, but it’s not useful for me to have that experience when also there are people who do struggle with this when they have like 30 grams in their own dishes straight away. So it’s like cool to have that experience, but yeah, it doesn’t, it’s not reflective of everybody’s experiences.


Absolutely. Certainly a wide range. This has been episode 117 of the Ideal Nutrition Podcast. If you haven’t yet left a rating or review, it is always greatly appreciated if you could do so, but otherwise thank you for tuning in.