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Written by The Thriva Editorial Team
8th Sep 2026 • 48 minute read

A wave of nausea mid-run, the urgent dash to the loo before a competition, a stitch that stops you in your tracks. Ever wondered why your gut turns against you during exercise?

Show notes

In this episode, Dr Patrick B. Wilson helps us reconcile with our gut when we work out. An Associate Professor of Exercise Science at Old Dominion University and registered dietitian, Patrick has dedicated his career to answering burning gut questions. He is also the author of The Athlete's Gut, which looks specifically at how exercise, diet, and psychology interact with gut function.

In our science segment, Patrick walks us through what the gut is and why it's so much more than a digestive tube. He explains what happens when blood rushes away from the gut toward muscles, why some forms of exercise (like running) tend to cause more symptoms than others, and how hormonal changes across the menstrual cycle shape what the gut does during exercise.

Patrick, Greg, and Charlie then go on to discuss how we should eat and drink around exercise in practice. Including:

  • The basic foundations of a gut-friendly exercise diet (21:15)
  • Are probiotics a valuable food supplement? (23:08)
  • What is the role of carbohydrates during exercise? (27:10)
  • How to approach hydration for 90+ minute workouts (29:20)
  • When to consider a low FODMAP diet (32:50)

Finally, in the experience section, we hear from listeners with their own gut dilemmas: when hydration actually starts to matter; what to do when the heat makes your usual run feel impossible; how to minimise nausea at max effort; and why a stitch shows up when you're working your upper and lower body at once.

If you'd like to send us your health questions for future episodes, you can email us a voice note or write in at themethod@thriva.co

Mentioned in today's episode

Transcript

Patrick: We think about training our bodies, whether it be endurance training, resistance training, focusing on your mental health. The gut does a lot of this stuff automatically for us. It's kind of a wondrous organ, and it oftentimes only occurs to us that it's doing much for us until something goes wrong. Right, then it's very apparent that things are not functioning the way they should.

Charlie: So today we're joined by Dr Patrick Wilson. Patrick is an associate professor of exercise science at Old Dominion University, where he also directs the Human Performance Lab. He's a registered dietitian and researcher, and his work sits at the intersection of exercise, nutrition, and gut health.

He's published more than 45 research papers, and he's also the author of The Athlete's Gut, which looks at how exercise, diet, and even psychology can affect our gut. Patrick's work isn't just about elite athletes. He's also interested in what happens to our gut when we exercise, why we sometimes get those not so pleasant symptoms, and what we can actually do about them.

Greg: When are you writing your book? The Hot Gut.

Charlie: I've just been negotiating with a few publishers at the moment. It's quite an in demand subject.

Greg: Backing them off.

Charlie: Yeah, yeah. They're knocking the door down, really. Which I'm not surprised about. No, it's obviously a topic in high demand.

Greg: And the conclusion is?

Charlie: Live your best life. Live your best life. That's it. Oh, I've just revealed it, actually. I've revealed what the only written sentence will be.

Greg: Anyway. If you have some sort of tummy problems during exercise, what do you think might be contributing to that?

Charlie: I think I briefly googled this and probably read the first few sentences. Didn't look into the science all that much. Shock. And is it about a redirection of blood? I think the blood is flowing to your gut maybe a little bit more, I think. Or, the look on your face is saying not correct.

Greg: We'll have to ask the guest about that, won't we?

Charlie: Oh, well, I don't know. Given the fact that you just frowned at me, I'm probably not gonna ask an expert that. Maybe you could ask him.

Greg: I'm sure we will get to that. But you have had those issues before. You've had funky tummy during exercise? Plenty of times.

Charlie: Yes, I had it really badly when I was racing triathlon. I think a lot of it was the energy gels.

Greg: Yeah.

Charlie: They just didn't sit well with me.

Greg: Didn't work for you.

Charlie: No. I've tried various brands of gels, types of gels when out training, and it's funny when people ask me for recommendations, it's always so personal. What works for me might not work for someone else. It's really dependent on your own gut.

Greg: So what's your strategy now?

Charlie: I do still use energy gels, but I use Maurten, and I ate four crumpets before a long run so I'm not hungry. Crumpets. But even then, like post marathon, I think because I had so many, I was just like, oh.

Greg: And what have you noticed when it comes to different types of exercise that are much harder on your tummy than others?

Charlie: I would say running more than anything. So cycling, I could probably cycle a long way. But then it's also weird, I can eat anything on a bike. I've eaten roast potatoes while cycling quite happily.

Greg: Chased those with a beer.

Charlie: I ate those along the way. Some pork pies, which I would never do whilst running.

Greg: This is the most Charlie thing ever. Tell me she's northern without telling me she's northern. Spuds and pies all the way around.

Charlie: But yeah, if I'm doing a speed session, normally it's not great. But I've also noticed as well, I had a really weird reaction once, it was probably about six years ago, a dehydration reaction that I've never had before.

Did a long run, was quite clearly dehydrated. And just about 10 miles in, maybe, I thought, oh my God, I'm gonna throw up everywhere. But had nothing in my stomach to throw up, and was in such a bad way. Managed to get home, but it was the overwhelming sickness I'd never had before. And I thought, well, this is it. I think my body's shutting down. And then googled it and it was like, oh, severe dehydration. Which is very, very rare for me, 'cause I drink a lot.

Greg: Yeah, it's a really interesting subject. It's something that I didn't appreciate until relatively recently. I think a lot of people would assume that if you are under hydrated, then if anything, that's gonna reduce the likelihood of having some sort of gut issue. But that is absolutely not the case. Under hydration, like over hydration, can cause gut issues during exercise, but for different reasons, and maybe we'll get to that in the episode with today's guest.

Charlie: Yeah, it would be interesting to get his thoughts on that.

Greg: We're focusing here mostly on recreational athletes, but I think a lot of people listening to this won't be athletes and they won't be doing very long exercise. And frankly, tummy problems are more likely to arise the longer the exercise is. And so for many, you don't need to do anything fancy around exercise in order to avoid gut problems. But just understanding something about the biology can help make sure that you keep danger pants at bay.

Charlie: Fab. Let's bring in Patrick.

Charlie: Hi Patrick. Welcome to The Method, we're thrilled to have you with us. So today we're gonna be talking about the gut. So if we could start with the basics. When we talk about the gut, what are we actually talking about, and what does a healthy gut look like?

Patrick: Yeah, so I guess I would think of the gut as an entire system that is meant to digest and absorb the foods that you eat so that you can thrive as a person. It's also this sensory defence system as well, that is really important for overall health.

What most of us think of as the gut, we think of the stomach, we think of the intestines, we think of the oesophagus, the mouth, but it's also the accessory organs. The pancreas, for example, which helps with digestion by secreting digestive enzymes. We also think about the nervous system element of the gut. It's kind of the second brain of your body, and it helps to regulate digestion and the speed with which things move through your gut, for example. Also think of it as a sensory organ. It interprets the local environment. And that includes food, other things you eat, but also germs, bacteria, viruses. It is gonna respond to those types of things. You wanna absorb the things that you're eating, 'cause those are critical for growth and development and health. But you also wanna keep out the things that are gonna pose a health threat. And that can be things like bacteria, viruses, or other toxins or chemicals that might be harmful in large quantities.

So, what is the healthy gut? My perspective would be it's one that is effectively digesting and absorbing the things that you eat, and also not causing you daily troubles because of unpleasant symptoms and issues. So think about maybe somebody with IBS or dyspepsia or reflux. It's gonna really affect their quality of life if they're experiencing those symptoms day to day.

So a healthy gut is effectively working the way it's supposed to, with an absence or a minimised amount of daily troubles in terms of symptoms and pain and discomfort.

Greg: Let's get into what happens in the gut during exercise. Lots of people experience gut related symptoms during exercise, getting a stitch, having gas, maybe having some nausea, or maybe even danger pants, God forbid. And some nerds have given this a name, exercise-induced gastrointestinal syndrome. What is it about strenuous exercise that can trigger these symptoms, and why is it that some forms of exercise, so running is maybe foremost among these, tend to produce worse symptoms than other types of exercise?

Patrick: Yeah, so exercise in total poses a stressor to the gut. You can think of it as a system that requires resources to run. Just like any other body system, it requires energy. It requires oxygen. Nutrients. So when your body is working during exercise, especially harder exercise, vigorous exercise, there's a demand for blood flow that needs to go to that working muscle to facilitate that.

As we increase our exercise intensity, oxygen goes up. A lot of that is directed to the skeletal muscle, and it means more blood flow is gonna have to go there. And because of that, the gut typically is gonna receive less blood flow than it otherwise would during mild exercise.

So there's more of a challenge to the gut in terms of its ability to self-regulate. And then you have these exacerbating factors on top of that. So the modality of exercise is thought to play a role. The physical jostling of going up and down a mountainside if you're an ultra runner, or if you're a cyclist, being over in a hunched over position, can cause maybe more reflux, and types of upper abdominal symptoms.

Heat and environmental stress is gonna be another element there. So the hotter it is, that's more blood that needs to go to your skin and the periphery to cool you off. So again, less blood flow to go to the gut. Altitude probably also gonna play a role because of less oxygen availability and delivery.

So it can be a combination of things. You've got the modality of exercise, you have maybe environmental stress like heat stress and altitude. So yeah, it's a combination of things that's gonna play a role, but what we do see is there's a lot of individual variability.

Some athletes seem more susceptible, while others can kind of almost eat anything and they don't have that many issues. So it probably, again, is this combination of risk factors plus individual susceptibility that leads to some athletes having more problems than others.

Greg: We'll get back to how this actually works in practice later, but it seems that most of us can train the gut to work better during exercise. People might have seen eating competitions where individuals can put away heroic amounts of food in a short period. They probably weren't born with that capacity. They developed it over time. And that is related to exercise as well, potentially. What do you think are some of the actual biological changes that underpin this improvement? And could this improve performance?

Patrick: So you can train the gut to adapt. It's a flexible organ system, like others. You can train your skeletal muscle, you can train your heart. So yeah, the classic example of competitive eaters shows you that at least from a tolerance perspective, you can dramatically change how much food you can tolerate to eat in a short amount of time.

Their stomach is maybe better relaxing and accommodating that large size of food. So that's one potential adaptation, is just better tolerance. And I think probably plays a role in athletes that you just get more comfortable with the ability to ingest food either before or during exercise. So that if your goal is to try and ingest a larger amount of, let's say, carbohydrate or fluid, you're better able to tolerate that and not let it interfere with your performance.

In terms of more functional things, another possible adaptation that is speculated is that you maybe get better absorbing some of these, let's say, carbohydrates. Maybe your body upregulates the doors that you use to shuttle these sugars from the intestinal space, the lumen, across the cell membrane into your bloodstream.

Anecdotally though, I think if you're going to, as an athlete, try and ingest a lot of carbohydrate or fluid as a part of your race plan, then it just makes intuitive sense to train that way, and get used to it, even just from the sake of a tolerance perspective. So is it gonna be beneficial for all athletes? Not necessarily. I think it really depends on the demand of fluid and carbohydrate you have as an athlete, let's say during competition. Do you require large amounts to perform well? If you do, then gut training is an integral part of that. If you don't require a lot, then I don't know that it's really necessary for most athletes to go overboard with the gut training.

Charlie: Okay, so I've done quite a bit of endurance training over the years, and hydration is something that crops up constantly. But what actually happens in the gut when we're dehydrated, or even if you drink too much, and how much does hydration matter depending on the type of exercise that you're doing?

Patrick: So dehydration can negatively impact gut function, in part because of, again, the issue around blood flow. So as you become dehydrated, that's probably also less fluid in your bloodstream. And it becomes, again, more difficult for your body to distribute adequate blood flow to all the organs that need it during exercise.

So especially, let's say you're in the heat, you're trying to cool yourself off, blood's going to your skin, but you're also losing a lot of fluid through sweating, because that's the way your body self regulates your core temperature. So if you're not adequately replacing fluid losses, it can eventually contribute to a sort of shutdown of the gut, or reduced gut function.

So that is a risk of under drinking during exercise, that eventually, and we're usually a couple hours into exercise if not longer, you can see again this nausea, feeling like things are kind of just sitting like a brick in your stomach. On the other side of things, there is a risk of drinking too much, and the primary risk is just that you're gonna feel overly full. You're gonna feel bloated.

So if, let's say you're sweating one and a half litres per hour, if you decided, hey, I want to try and replace all that, that's a recipe for probably drinking too much. Yeah, it's a lot of fluid.

The goal is not to fully replace, but maybe try and prevent excessive dehydration. And it's a kind of a delicate balance. During longer duration exercise. If you're going for an hour or two, you can probably rely on thirst in most cases and not worry about dehydration, 'cause it's not long enough to accumulate. But as you get beyond two hours, it's more probable that mismatches in sweat rates and fluid intake can add up.

Greg: Gut problems are quite common among some athletes, but they're also relatively common in the general population nowadays. And I imagine there are some things about exercise that are good for the gut. So how does the gut health of athletes, for the most part, compare to the general population?

Patrick: Yeah, there's some overlap. I think one thing to keep in mind is that athletes are also just everyday people. So you see that if they are experiencing more gut problems day to day, you also see that translate to what's happening oftentimes during exercise for them.

Now, what are some positive things that can happen to the gut with respect to physical activity and exercise? Assuming you're eating enough, one of the positives is that you tend to see maybe fewer issues of, like, constipation, for example.

Some physical activity and exercise helps to facilitate motility. So like when people are in the hospital and they maybe have come out of surgery, one of the first things that staff will do eventually, when they're ready, is get people moving. And in part that's to help get their gut also functioning. Another benefit potentially is on the gut microbiome. There are a host of studies kind of showing that you generally see probably more diversity in the microbiome for athletes. It could be due to a higher amount of certain bacteria and species of bacteria.

It might be differences in diet. Athletes eat differently than non-athletes. They may be eating more carbohydrate, they may be eating more fibre in some cases. And then you also see some differences in the gut microbiome, which we think may tie into health and performance. Can you manipulate the gut microbiome specifically in a way that facilitates health and performance? Perhaps. But I think that is an area where there's a lot of research to be done at this point.

Greg: And maybe some of the differences between athletes and non athletes also relates to, if athletes are spending more time outdoors in nature, for example, then maybe they're exposed to different bacteria and fungi and so on, and that has some small effect on the gut microbiota.

Patrick: Yeah, I would agree with that. The general environment that somebody lives in, trains in, especially higher level athletes are spending a lot of time in whatever environment they train in, is gonna have an impact on the things they're exposed to. And that's ultimately gonna maybe impact their gut health in some way.

Charlie: I think some of the grubby lakes I've swum in at times have probably contributed to that. Salford Quays, the ship canal. The next question is for any women listening. So a lot of women notice changes in their digestion around their period. Things like bloating, constipation, potentially needing to go to the loo more often. What actually happens in the gut across the menstrual cycle, and does it follow a fairly predictable pattern?

Patrick: Yeah, there's definitely impacts. We see across the menstrual cycle that bloating and constipation, abdominal cramping, I think are the few that really stand out as varying pretty regularly across the menstrual cycle.

I'm not an expert expert in the menstrual cycle, so I'm not gonna comment on specifically what parts of the menstrual cycle you're gonna see those exact differences. But you do see that there is a variation there across the menstrual cycle, which explains partly why there's differences between men and women in the severity of certain symptoms, and some of these driven by female physiology, fluctuations in hormone levels.

'Cause even across the menstrual cycle you can see changes in rates of how fast things pass through the small intestine and the large intestine, for example. So we do see that not only are symptoms different, but the actual underlying function you can see change as well. So like constipation. If you see a high rate of constipation in a particular point of the menstrual cycle, it's probably gonna correlate to reductions in motility, or reductions in how fast foods are going through the small intestine and the large intestine.

And that may be something to consider with female athletes, just to be aware of that, number one, as a practitioner or a coach. And then just keep in communication with your athletes as much as they're open to talking about that. Having a conversation about whether or not their approach to nutrition and other things may need to be adjusted to account for those kind of variations that they might experience across the menstrual cycle.

Greg: We move on to the practice section. Patrick, I'm gonna play back what we've covered so far. You spoke about how the gut is a continuous muscular tube from the mouth to the backside, but it also includes various accessory organs, and it's closely connected to other systems, including the nervous system, and that helps explain why, if someone's feeling anxious, for example, that can manifest as gut symptoms. Those symptoms can be caused by various factors. One of those, it's important, is blood flow redistribution, so working muscles and so on away from the gut. And another is that during exercise your body cranks out more stress hormones. Another is just the actual motion that's involved. But then there are environmental factors too, such as heat stress. We can train the gut to function better during exercise, and the best evidence is greater tolerance of food in general.

Say participating in a race, both under and over hydration can contribute to gut symptoms, but for different reasons. Gut problems are quite common in exercise, but that tends to be related to pre-exercise gut symptoms, and overall exercise is associated with relatively good gut health. And then female symptoms will fluctuate during the menstrual cycle, but as an individual you need to work out what works for you.

Charlie: So moving into the practical side of things, there's a lot of advice about gut health online these days, and it can be hard to know what's actually worth paying attention to. If you wanted to give us the basic foundations of a healthy diet for the gut, what would you recommend?

Patrick: So there's several elements to think about. One would be supplying enough energy, particularly if you're an athlete, having enough food and energy on board to support general health. But that's also gonna translate to gut health. So if an athlete, for example, is participating in a sport where body weight management is kind of a common thing that's considered, and oftentimes athletes are targeting weight loss reduction at various periods, if they're not eating enough to support their training plus their just baseline energy expenditure requirements, you do see some negative effects.

Greg: And those tend to mimic some eating disorders like anorexia. And I think I know people personally very well who have had those symptoms and have gone down various rabbit holes trying to identify what it was. Was it non-coeliac gluten sensitivity? What was going on? Why was I so backed up? And ultimately it was just low energy availability. It was a history of not eating enough to match the energy expended in various activities.

Patrick: Yeah, that's something to kind of keep just in the back of your head, about the importance of adequate energy availability for basic gut functioning.

So that's one part of it. Another thing would be eating a variety of foods that supply the gut microbiome the fuel to be able to thrive and be diverse. A relatively good amount of dietary fibre typically means a diet that has a fair amount of plants in it.

So to me that's another element that tends to be kind of consistently associated with generally good gut health and regularity, going to the bathroom on a regular basis. But those are a couple of things that kind of come to mind. A lot of people are interested in supplements. Personally, I don't think the evidence is all that great for most supplements in gut health, despite what some may claim. Probiotics, I think, can provide some benefits. I'm not against taking probiotics, but the weight of the evidence isn't overly strong to say that it's a necessity for most people, if they have a baseline diet that includes some fermented foods and the actual prebiotics, or the substrate for those bacteria to thrive on.

I'm a little bit sceptical of the value of probiotics for everybody, although there are some, I think, individual benefits that can be achieved by taking probiotics in some cases.

Charlie: I'm glad you said that, 'cause I take one every day.

Patrick: I've gone through phases taking probiotics and not. I think for people who are physically active and maybe susceptible to getting respiratory tract infections, or if you have some regular gut issues, there's some evidence that it can be helpful, but there's also not a huge amount of risk. I'm kind of more speaking to just the idea that everybody should be taking a probiotic. I don't subscribe to that.

Charlie: I suffer with psoriasis. So I take it 'cause that typically comes from an imbalance in your gut. So yeah, I take it for that.

Patrick: Maybe in the future we'll get better at personalising them according to the context. And certainly you are unlikely to be harmed by including some fermented foods now and then. Yoghurt, kimchi, kefir, whatever your favourite is.

Greg: If we go back to exercise, then, can you give some general guidelines about what and when to eat before exercise to support performance and try and keep digestive complaints at bay? And maybe touch on some of the factors that could influence what's most appropriate.

Patrick: Yeah. So when I'm making decisions about, for example, what I eat before I exercise or train or compete, we think about a few different considerations. One of 'em is what's the intensity of the exercise? What's the environmental context or the situational context, like what time of day is it? Are you training when you wake up in the morning? Or is this at 10:00 AM or 3:00 PM? So the timing of exercise in relation to when you might regularly eat a meal. Also thinking about competition settings. There's also the added element a lot of times of anxiety and sort of the jitters, and some of the digestive things come along with that, that you need to maybe consider.

So to give some practical examples, for regular training, day to day training, personally for me, I'm not overly restricting things like fat, solid protein, fibres, those types of nutrients in my feedings or meals, assuming I'm eating two to three hours beforehand. And I'm not eating a 2,000 calorie meal. These are reasonable sized meals. Maybe we're talking about a 600 calorie meal or something like that, a couple hours or two to three hours beforehand. If you're getting up in the morning and exercising within an hour or 45 minutes, that's a different story.

And you gotta think through what's the intensity, what's the duration of what I'm doing? As a rule of thumb, the harder it is, the longer it is, the more critical it's gonna be to maybe have something that supplies energy for you, primarily carbohydrate. And the closer it is to the start of that exercise, probably the more easily digested you want it to be.

So whether that's a beverage, a gel, or something along those lines that you can take, get in, and your body can kind of digest and assimilate pretty easily. Now, if it's a lower intensity session in the morning, I may go out and not eat at all. Some fasted training here and there is not necessarily a problem, as long as it's not done in excess, and as long as you're only doing that when it's kind of the lower to moderate intensity type training.

So yeah, there's a few different factors I think just to think about. Like I said, intensity, duration, and whether it's something that's competition or training. Those are all things that I would think through before I make a decision about what I'm going to eat, what quantity, and what the timing is in relation to that exercise.

Charlie: So obviously we've just covered some general food advice there, but it'd be great to get some more specific tips. So if we were to take someone who does a lot of endurance exercise, and say they're going out for a long training session and they've always just drunk water on their run or cycle 'cause they're not used to eating or drinking much whilst they exercise. If they wanted to improve their performance, where should they start, and how important is carbohydrate?

Patrick: It's gonna be more important when it is longer duration and it's higher intensity. And you're looking at, let's say, multiple days of higher training load. So you can't just look at one workout in isolation. You also have to consider what did I do the day beforehand, and maybe what am I doing the next day? So if you're stacking multiple days of volume and intensity, yes, it is gonna be very important to get in carbohydrate before, probably during if it's long enough, and certainly afterwards.

So for me, for example, I actually did a workout this morning, a kind of a threshold run that lasted about an hour. I did it probably stupidly at 10:00 AM. It was roughly a 90 degree heat index in Fahrenheit. So not the most pleasant conditions to do a threshold run in. But when I got up this morning, I ate basically a bowl of Chex mix with some sugar on top. I had a little bit of protein, with milk and whey, and this is probably three hours before the actual workout.

And then within about 45 minutes of the workout, I had some fruit snacks. I had basically some fluid with some caffeine and some flavouring. And then during the workout, halfway through, typically I'll take a gel. Now I probably don't need all that carbohydrate for just that workout, but I'm also increasing mileage at the same time. I have more to do the next day.

And this weekend I'm gonna do a 13 mile run. So I'm trying to be cognisant of not only what is important for this workout, but what else do I have coming up. So it is tricky to sometimes balance all that. It comes with experience, knowing your body, and maybe working with a dietitian or somebody who can help you plan through that. 'Cause if you look at just workouts in isolation, sometimes it can be a little bit challenging to look at the broader picture as well, not just one workout individually.

Charlie: And just to come back to hydration, are there any simple rules of thumb people can use to work out whether they're drinking enough when they exercise? I've heard about sweat tests and weighing yourself before and after.

Patrick: I think for most people, if the exercise session is 90 minutes or less, drinking to thirst in most cases is gonna be sufficient. Assuming you are starting that workout or that training session in a well-hydrated state. In terms of sweat testing, that sounds complicated.

I think it is helpful to have a sense of how much they're gonna sweat under different scenarios. And really that just means weighing yourself before and after that run or that cycling workout or whatever you're doing, also accounting for if you drank any fluid. So if I lost, say, four pounds over the course of an hour and a half, that gives me an indication of how much fluid I've lost.

'Cause really in that time span, all that weight loss, unless you stopped to go to the bathroom, you know, had an urge to have a bowel movement, all that weight loss is gonna be essentially fluid. So you can work out what your sweat rate is. There's online calculators you can put this into, like the Gatorade Sports Science Institute has an online calculator to help you with this.

If you know that sweat rate, you can then come up with a plan to try and replace a proportion of that sweat. I wouldn't advise a hundred percent in most cases, but maybe 50 to 75% of what you expect to lose. That's oftentimes a reasonable amount to try and replace. If your exercise is gonna be longer than an hour and a half, or especially longer than two hours, or if you're competing in a marathon or a long distance cycling event, or an ultra race, that's when I would say a more rigid, structured replacement plan can be helpful. Especially if it's gonna be a hot, thermally stressful environment that you're competing in.

Charlie: And would you recommend, obviously if someone is looking to start, and say the calculator said 50%, would you recommend someone did it in stages? So maybe go with 10 or 20%? I'm just thinking, if all of a sudden now I was to try, I don't drink when I'm on a long run. I did a marathon without drinking anything, which I know is probably not recommended, but.

Greg: And then she rehydrates with beer after.

Charlie: Alright, Greg, don't out me on the podcast. I did have quite a bit of Guinness after. Again, not medically recommended. But I'm just thinking, if someone said to me now all of a sudden to go and try and replenish 50% of the sweat that I lost during that marathon, I would be in a whole world of pain.

Patrick: Yeah. So I think it comes back to that tolerance piece of being able to train yourself to be able to handle that fluid. And like you said, I think it starts by smaller amounts and then working your way up as much as you can do feasibly. There's no set percentage that is right for everybody in terms of replacement.

But I think having an idea of what your sweat rate is under different environmental conditions, and you've got, let's say, a marathon coming up and you know your pace is gonna be about that, you can look back at your historical sweat rate and say, well, it seems reasonable for me to maybe drink 500 millilitres an hour or 700 millilitres an hour to try and make sure I prevent myself from becoming dehydrated by the time I get to mile 20.

So that's the way I would think about it. Again, for most training sessions and competitions that are less than 90 minutes, not worth it to go through the calculations and have to think about sweat rate. So I think be reasonable. If you're gonna do these calculations and go through the work, it would be for situations where it's longer, intense exercise.

Greg: Moving on. There's a big range of gut disorders. Some of those aren't that well understood. We certainly don't have time to try and address all of them now. But with that said, there's some diet changes that commonly work for people. For example, it's quite common to see people recommending low FODMAP diets nowadays. FODMAP, for listeners, that's an acronym for different types of short chain carbohydrates that get readily fermented by microbes in the gut. And the result can be things like gas and bloating. So what are some of the nutritional changes that people with gut symptoms during exercise commonly find helpful?

Patrick: Yeah, and I think it'll depend on the specific symptoms that somebody's experiencing. But as you kind of mentioned with the FODMAP diets, oftentimes that's if somebody has, especially, bloating, a lot of gas, maybe loose stools. Sometimes what it kind of means is those carbohydrates or those sugars, like fructose and lactose, for example, if you're eating a lot of those, if you don't absorb them, eventually they make it far into your small intestine and into your colon, where they normally get absorbed prior to getting to that part of your gut.

So if they're still there, what it means is water again is gonna get kind of pulled out into the luminal space, the tube space. And that can cause cramping, again, it can cause loose stools. The bacteria are gonna feed on those sugars, that's gonna cause gas to be produced, bloating, gas, flatulence. That can be a side effect.

So a low FODMAP diet is something to consider if someone is having significant quality of life issues, the symptoms are really hard to deal with. I would advise that that's a viable approach if you're working with healthcare providers that can help you with that. The only hesitation I would have is long term, we don't really understand well what is that gonna do to your microbiome, for example. Are there gonna be negative effects that we would be concerned about if you went on a very strict low FODMAP diet and you're not giving those bacteria kind of the nutrients they like to feed on?

So that's one example. For somebody who's having dyspepsia or reflux, what they may implement or try is gonna be different. They may have to start to think about what are the foods that cause reflux? It could be spicy type foods. It could be chocolate, it could be fatty foods, other things that may predispose you to having more reflux, and they have to be maybe more aware of those foods, particularly around the time of exercise.

So yeah, it depends a lot on really what are the symptoms. What is the specific gastrointestinal kind of condition will dictate what are the possible nutrition and food related things you could do to at least minimise the symptoms. It's generally not gonna cure these problems, but it may at least minimise some of the symptoms.

Greg: Sorry for the interlude, but give us a moment to talk about Thriva, the company behind this podcast. Charlie, take it away.

Charlie: Oh, no pressure. So what we do on The Method is try and help you play the long game with health. You know, the whole longevity thing.

Greg: It's a very scientific view.

Charlie: I am trying, Greg. I'm trying. Well, basically, Thriva is built to help you on that journey to long-term health too. They offer tests you can do at home that give you a picture of your blood markers. The goal is to see where you're starting from, make changes, and retest a few months after.

Greg: They also have a comprehensive app. You can sync your wearable devices like a smartwatch or smart ring, information about your health such as your goals, your exercise habits, how you eat, and collate all of that in one place. And this way, over time, you can see relationships between things. Identify what's actually working.

Charlie: It is a really simple tool to turn good resolutions into habits that really stick. So check them out at thriva.co. Links in the show notes below.

Greg: Now back to today's episode.

Charlie: So we are going to head into the experience section now, which is where we're going to put forward some questions from our listeners. So the first one, oh, it's actually from Lise.

Lise: Yes.

Greg: Cameo.

Lise: This is rare, but it does happen occasionally that I have a question that I want answered. So I sneak one in. My question was about hydration, because I've gotten back into running and I run three times a week. The running sessions are between five and 10k every time. So I'll say do two sessions that are maybe between 30 and 45 minutes, and then there's one that's slightly longer, that goes above an hour, so on and so forth. I don't hydrate, 'cause my running has always been a very minimal thing where I have just one piece of equipment to have my phone and my keys.

And so I've always thought, oh, if I'm buying more stuff and whatever. I live in Scotland, so my conditions are pretty decent. But over the course of the summer, there are times where I was travelling to see family in continental Europe and where the running conditions were just too hot to be able to maintain my usual pace or my usual distance. And it felt like not hydrating was actually a little bit unsafe at that point. So I wanted to ask, what is the recommendation to adapt to heat, and also how and when should I consider starting to hydrate during my runs?

Patrick: Yeah, I think if most of your runs are the 30 to 45 minute time range, it's not necessarily imperative that you do drink during those runs. I would say focus on beforehand to make sure you're well hydrated before you start. And then also make sure once you're done, you are drinking enough fluid afterwards, and also throughout the rest of the day, to maintain good overall hydration.

So again, you theoretically could measure your weight before and afterwards and see how much you lost, and that would tell you kind of how much you need to drink maybe over the next two to three hours to get yourself back to baseline. If you don't want to weigh yourself, 'cause certainly people may not always be wanting to weigh themselves all the time for any variety of reasons.

Lise: I was gonna say, I actually don't own scales either. This is, I don't weigh myself ever, but go on. Sorry.

Patrick: Yeah, fair enough. And that's, I think, the other alternative, is just to pay attention to the number of urinations you're having in the day, and kind of the colour and volume of your urine. So in a well hydrated state, most people are gonna be urinating probably every two to three hours, their urine colour should be relatively clear, not completely clear, but you're producing a good enough amount of urine that it's really a sign that you're drinking enough to sustain good health, good cognition. You're not dehydrated.

So if you're finishing your runs and the rest of the day you're only urinating a couple of times, that might be a sign that you're not drinking enough afterwards. To be honest, I probably did not drink enough after the run I just did this morning, despite knowing that I should. Sometimes if you don't really pay attention to that sort of thing, it's easy to fall behind a bit. But urine colour, volume, is a relatively easy indicator that you can use, separate from weighing yourself.

For the heat preparation, I think most people, if you're starting to exercise more and more in the heat, you'll naturally start to kind of acclimatise over time. I think just be wary of the intensity of exercise you're doing, especially early on when you're exposed to heat. So you want to gradually ramp up either the intensity or the volume as you're exposed to that heat. You don't want to go out the first day when it's 90 degrees Fahrenheit or whatever Celsius that ends up being. I think that's maybe low thirties.

Lise: About 35 or 37.

Patrick: Yeah. Yeah. If it's that hot, then be a little bit cautious, especially the first couple of times. But yeah, over the course of a week or two, if you're regularly working out in those environments, you will start to become naturally more heat adapted, and the things you're gonna notice, you're gonna sweat more, you're gonna sweat earlier, and you're gonna feel more comfortable in that hot environment. It's still not gonna be pleasant probably, but it's not gonna be as stressful in terms of how you feel.

Lise: Yeah, this is great, I appreciate it. I will say that I tend to run in the evening, which actually makes it better, 'cause I tend to have a little sleepy tea before bed. So there will definitely be a hydration post run.

Patrick: Nice.

Lise: But anyway, thank you for answering my question.

Patrick: Sure.

Charlie: The next question is a voice note from a listener called Davis.

Davis: So my daughter is a really good runner and she really struggles, particularly as she's got older, with feeling nauseous in races. She can be running really, really well, hit the hill, and then gets to a point where she even has to drop out sometimes. And it's something that we kind of know is gut related, but never really managed to get to the bottom of it. We've sort of got to the point where we think it may be something to do with fuelling, and fuelling during the week and just eating well, and kind of hopeful that as she grows and actually stops growing, maybe it'll get more under control. But it'd be great to know what the conclusions might be. The cause and the symptoms seem kind of clear, so it's when she's going absolutely max effort, she feels nauseous. And then the contributing factor is probably growing and being low on energy. What can she do? She's 16. And she's a really, really good runner, but this is one frustrating thing that can sometimes hold her back.

Patrick: Yeah, that's honestly a pretty common anecdote or message that I've gotten over the years from people, about nausea that they experience that causes them to either drop out of a race or they're unable to perform the way they want.

So there's a few things going on there. One is age, and it does seem like younger athletes are more susceptible to, particularly, nausea with high intensity exercise. It may be due to age related differences in stress hormones and sensitivity to those stress hormones. So there's a piece there that you can't really change, other than getting older as you go along.

So he also alluded to some things that might contribute or exacerbate nausea. It could be dietary related. A couple things I would look at would be, if an athlete is undereating or has low energy availability or something along those lines, that can also be associated with increases in stress hormones. Because if, let's say, you're not eating enough, that would cause your body to react to produce more of its own glucose. 'Cause maybe you're not eating enough on a regular basis. So we see this with fasting. If you fast for long enough, nausea levels oftentimes will go up, in part because of the stress response. When people get hypoglycaemic, nausea can be a common symptom that comes along with that. Not saying that that's what's going on in this particular case, but that is something to at least consider.

Anxiety and stress. Some of my lab's research has looked at that, and it is something that is commonly associated with a host of gastrointestinal symptoms, but it's definitely nausea. So the more anxious athletes tend to feel day to day, we see that they're at a greater risk of experiencing these types of issues. Is an athlete kind of more anxious prone? If they are, then maybe working with a sports psychologist, or trying some low risk things like slow deep breathing.

Blood flow issues can certainly be a contributor. That's a little bit more difficult to investigate. That might require a consultation with a gastroenterologist, for example, to really actually diagnose something that would be more anatomical or blood flow related. There's no easy way to do that on a questionnaire or on a basic screening, so that's a little bit more challenging.

So yeah, those would be the things I would look at. Undereating, psychological stress, race anxiety, caffeine or stimulant use. There's a lot of things that contribute to it, and it's tricky to really identify what in one individual case is going on.

Charlie: The final question is from Vicky in Essex, and I'm curious about this 'cause I actually dunno what causes them. So they've asked, why do I always get a stitch when I do vigorous exercise? I've tried everything from not eating before workouts to only sipping water during, et cetera. The list goes on. It seems to happen when I'm moving my upper and lower body simultaneously, eg. for burpees or on the assault bike.

Patrick: Yeah, there's a few theories on the side stitch. ETAP is what the scientific jargon is, exercise-related transient abdominal pain. Probably, I think, the leading theory at this point is it's an irritation of the lining inside the abdominal cavity that can come from some of this movement, this torso movement. It can also be worsened by things. For example, there's a study that gave people a highly concentrated carbohydrate beverage before exercise in a large volume, that seemed to exacerbate it.

So there is some maybe element of what you eat. Concentrated beverages or too much food too close to exercise seems to maybe expand your stomach, and that can maybe put some extra compression or stress on that lining. Diaphragmatic breathing seems to be helpful in some cases. There's some studies that have looked at breathing through pursed lips might be helpful, wearing a supportive belt around the waist.

So the leading theory is this kind of irritation of the lining inside of your abdominal cavity. And it's a frustrating one, 'cause it is hard sometimes to get rid of. But diaphragmatic breathing, making sure you're not eating too much close to exercise, working on core strength. That's kind of the interventions at this point. A study we did found that athletes who tend to be more anxious also had more severe ETAP. So again, maybe there's a connection with anxiety that could be a source of intervention.

Charlie: So would running it off, 'cause I've heard run it off, or stand with your hands above your head. Or pinch, it was another one. Stand and pinch your side. I've done that before. That doesn't work.

Patrick: Yeah. I mean, you could try it. I don't know that it's gonna do anything, and maybe it's a placebo effect and it helps in some shape or form. But it's a tough one. I mean, most of the time athletes just have to slow down and reduce their work rate and then try and work through it. It's difficult to rid it once it's there.

Charlie: Me and my friend were running last week. We did 19 miles after work and she had a terrible stitch and was running around with her hands on top of her head down the road. I thought, people are gonna think we look absolutely mental.

Patrick: For me personally, it tends to happen most often when I do eat too close to, especially, a harder run. That's, for me, the susceptibility seems to match what some research has shown, that you gotta be a little bit careful about what you're eating in proximity to when you're running, if stitching is something you commonly experience.

Charlie: So one final one. If listeners can take one thing away today from this episode, what would you want it to be?

Patrick: I think just an appreciation of how important the gut can be to performance and health. It still can be an afterthought sometimes. You know, we think about training our bodies, whether it be endurance training, resistance training, focusing on your mental health, all important things.

I think the gut does a lot of this stuff automatically for us. It's kind of a wondrous organ, and it oftentimes only occurs to us that it's doing much for us until something goes wrong. Right, then it's very apparent that things are not functioning the way they should. So yeah, I think just an appreciation for how important it is, and how sometimes underappreciated and an afterthought it can be. And I guess do what you can to take care of it. Just appreciate it.

Charlie: Amazing. Thank you so much for your time. It's been lovely to chat to you.

Patrick: Yeah, it's been very fun. I appreciate the invite.

Greg: Thanks, Patrick.

Charlie: Take it away on the takeaway.

Greg: Charlie, what are your takeaways?

Charlie: I'm just rereading my notes, my rustling of my paper. I didn't realise actually how much heat had an impact on it. I've never really considered that. I've always thought it was the intensity of exercise, never factored in. 'Cause it's been a hot summer, hasn't it?

Greg: And there have been a few studies that have tried to actually put a number to that, identify the proportion of the symptoms that people experience that is explained by heat stress. And the number suggests that it contributes a lot. So I'm sure it depends on the person and it depends on just how severe the heat stress is. But it is a really big factor, actually. And some of that is because of dehydration, but some of that is 'cause of other factors.

Charlie: Yeah. I didn't factor that in. Also very interesting about athletes' exposure to different environments and the impact that can have on the gut. I do think about, there's probably some, if I'm cycling, I drink from a water bottle. It's got loads of road dirt on it, right?

Greg: I think there's been work looking, for instance, at rugby players and the diversity of their gut microbiota, finding that it's pretty high, and also that there's maybe some concordance between players on the same teams.

Charlie: And yeah, the only thing, 90 minutes or less, drink to thirst.

Greg: Yeah, most of the time drinking to thirst works.

Charlie: What are your takeaways?

Greg: I think number one is that how your gut is before exercise is gonna strongly influence how it is during exercise. And since most people don't exercise for 90 minutes or longer, the majority of us should just focus on what happens before exercise and after exercise. So going into exercise being adequately hydrated, having a meal or a snack that's gonna fuel the exercise appropriately but also not cause symptoms, and then refuelling appropriately post exercise.

And then for athletes, there's this concept in sport science popularised by people like James Morton, of fuelling for the work required. But I think related to that, something that Patrick mentioned, is you have to consider the slightly longer term too.

So I'd be thinking about the whole training cycle. What's the work that's coming up in the subsequent week? Because if you're just focusing on the individual session, then you could shoot yourself in the foot by accident, because maybe you've got a few sessions coming up that are actually really quite taxing and you've got a bunch of other things going on in your life. And if you turn up to those depleted, then you could come down with an upper respiratory tract infection or something. So just consider the longer term as well.

Charlie: Yeah, I suppose I think I'm probably guilty of that, thinking, oh, it's only a short run, I don't need to fuel it massively. Not factoring in that 48 hours later I've got the big session and really probably should be fuelling for that a day or two before.

Greg: Indeed.

Disclaimer: This information is for general educational purposes only and isn't a substitute for professional medical advice, diagnosis, or treatment. Always speak with a qualified healthcare professional first if you have concerns about your health.

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