Episode 3 - Pre-Training Nutrition: Should You Eat Before Exercise?

Pre-Training Nutrition: Should You Eat Before Exercise?

In this episode, I want to talk you through one of the biggest issues I see faced by triathletes...fuelling for training. And why it’s so important to have a specific strategy for different types of training sessions. 

In this episode you will learn:

  • Should you eat before exercise?
  • And if you do, what should you eat?
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Fuel use during different intensities of exercise

Source: Romijn et al. 1993

Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration

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Episode Transcription

EP 3 – Should you eat before exercise? And if you do, what should you eat?

Hello and Welcome to this episode of the Triathlon Nutrition Academy Podcast. I am so excited to be here! I really hope you’re enjoying it. If you have anything you want me to talk about, just send me an email – [email protected] and hit me up. Let me know what you want to know about and I'll cover it for you in future episodes.

Now today on the podcast, I want to talk you through one of probably the biggest issues I see faced by clients when it comes to nutrition for triathlon. One of many but you know, one of the big major ones that if you do a good job here, it can really make so much difference to your training and performance.

So today, this episode, I want to talk to you about pre-training nutrition. So should you eat before exercise? And if you do, like what should you eat?

What I see with clients is they've either may be suffered with really bad gut upset during a session, it might be vomiting, or diarrhea or a stitch. And so they completely avoid eating before training. Or the other thing that people commonly feel is really flat with no energy to push through that back end the hard part of the training session when really that's when you get the most performance gains. And that can feel totally horrible. It can be really embarrassing. If you're having to run to the toilet all the time. And you're not really maximizing your training potential. You may not know it also, but you can increase your risk of illness and injury. In the worst-case scenario if you're not doing a good job with your pre-training nutrition.

So my goal with this episode today is to get you a few wins on the board. I want your gut to feel comfortable and confident before you start and turn up for a session. So you're not feeling too full, you're not worried about running to the toilet or choosing your run routes based on where the toilets are. And I want you to feel primed and ready to train well so you've got so much energy because I want you to feel like a supercharged triathlete. I want you to feel comfortable and confident in your plan and training. And you know, ready to train hard, race hard without having to stress about needing to run to the toilet or feeling bloated or pain or any of those things. Because what I see commonly with clients is they either don't eat at all, they eat the same thing across the week, or they have absolutely no idea and have no strategy and plan.

So one of the things they come and see me for is to actually get some structure and strategy to their nutrition across their training week. Because we know with triathlon, you've got to train for 3 disciplines. Not every day is the same. In fact, most people, their training program looks completely different every single day.

So if you don't have a pre-training strategy, you might be missing some key adaptations that you have. And you might also have some negative implications on your bone health because we know that we lose calcium in sweat. So there's some particular nutritional strategies that you can implement to actually help attenuate the loss of calcium in sweat. And that's particularly important if you're a female or a Masters athlete, and I use the term masters as a term of endearment, don't take that the wrong way. You can also block iron absorption, depending on the nutritional strategy that you choose. Because you do have an increased hepcidin response with exercise. And you can implement some nutritional strategies to assist with that to help maximise iron absorption.

If you don't have a pre-training strategy, you're also potentially setting up your day on the wrong foot. Sometimes when we fall into a bit of a hole in the afternoon, or we feel like we need a nap, or we're really craving sweet. Sometimes that's an indicator that your pre-training nutrition and what you do earlier in the day is an issue. It could be pre-training, during, recovery and the other foods that you choose. But generally that sort of sensation or feeling of just complete exhaustion after lunch where you just need a nap but instead, you probably can't because you're at work, so you might be craving sweet foods there or reaching for the cookie jar. Then I'd have a look at what you're doing right at the beginning in the day and with what you're doing pre-training.

If you're someone with big energy needs, and you don't have a pre-training strategy, then you're missing the opportunity here to get the right nutritional foundations or blocks laid. Because that's just another opportunity to eat for you. If you've got a whole lot of calories that you need to get into the day and you're not starting that until later, then you are definitely missing this opportunity here.

With the wrong pre-training strategy, you could be giving yourself gut issues during training. So hands up, you know who you are, if this is you. But you're the type of runner that knows where every toilet is on your route. Or you know that at like the 6km or 7km mark, that's when you're going to need to stop and find a toilet. So what you do pre-training here, and you know potentially also the other food choices that you're making right across your day and your week, that could be impacting those gut issues that you get when you're training. I know a lot of athletes that will avoid dairy here, because they think that that's the problem. But potentially it's other food groups that are causing your gut issues. So it's definitely worth investing some time with a sports dietitian to explore that further and figure out what the problem is and fix it. Because you shouldn't have to suffer through gut issues when you're training. A lot of the problems can be fixed with proper nutrition.

Now, my goal for your pre-training nutrition, there's two things mostly, I want you to feel primed and ready to train well. So you're full of energy, you're not concerned that you're going to hit the wall or bonk in the back end of a session. And you know you can push through right to the end. The second one is that I want your tummy or you gut to be comfortable. So I don't want you too full. But I also don't want you starving. That's also not useful, because then all you're going to do is think about your next meal while you're training. And I also don't want you to be uncomfortable to the point where you need to stop and go to the toilet halfway through a session, if you know, gut problems are something that you need to deal with.

So as a general guide for fuelling your sessions, I think you want to have a different strategy depending on what type of session it is. So each different session should have a different nutritional strategy to support it. And whether you eat before exercise depends on many factors.

So it depends on how long the session is. You might want to eat before much longer sessions whereas something shorter, you may be able to get away with doing it fasted. The intensity of the session also plays a part in whether you fuel or not. And we'll talk a bit about the science behind that in a second. The specific goals of the training session. So whether it's just a recovery session under an hour, easy run, you know, nice aerobic pace versus what I call ‘performance’ sessions. And they're designed to drive metabolic adaptation. So I'm thinking like speed work or intervals. Whether it's running or cycling or swimming and also more race-specific type sessions like bricks and runs off the bike. They are performance sessions. You're trying to drive a performance enhancement out of them. And so you want to have a different nutritional strategy for something like that compared to a long, slow run where we're building more of a diesel engine.

Whether you eat or not before exercise also depends on your personal body composition goals. So like, for example, are you somebody that wants to lose a few kilos of body fat? Or are you someone that really struggles to keep weight on? I would do something different for each of you, depending on what your body composition goals are.

So if you're sitting there and you're like, “Oh crap, I just eat the same thing all the time.” or “I have absolutely no friggin idea what I need to be doing” then you need to listen up. But before I get into too much of the details, I think it's really important that we take a bit of a step back here and get an understanding of the type of fuel that we utilise during exercise. Because this helps us to decide whether we fuel up for training, and then also how to eat during training sessions.


Let me know if this sounds like you. Do you feel exhausted by the end of the training week? Do you crave sweets in the afternoon and feel like you need a nap? Training for 3 disciplines can be absolutely exhausting if you haven't dialled in your nutrition. It can be frustrating when you can't quite piece together the solid race performance you know you're capable of. And confusing when there's so much information out there. But you're not sure what's the right method for you.

My goal for you is to unlock your true potential and feel like a supercharged triathlete. Firing on all cylinders full of energy and not only smashing quality training sessions, performing in every race too. If you're finally ready to start nailing your nutrition, join a powerful community of like-minded athletes in the Triathlon Nutrition Academy program. Head to dietitianapproved.com/academy to check it out now. For less than the cost of a coffee a day, you will finally have a plan for your nutrition instead of winging it and hoping for the best.


So let me get a little bit nerdy here. During exercise, we burn a combination of fuels and the main two are carbs and fat. Now the duration and intensity of exercise, so how hard you're working, that determines the type of fuel that we use. And that knowledge helps us to decide what to eat before training and also how aggressively to fuel during training.

So I'm going to talk you through a paper and a graph from 1993. It's really good science. And I'll put the graph in the show notes so you can have a look at it but I'll talk you through it. Because I think this is a really good important foundation for you to have as an athlete is to understand the type of fuel that you use at different intensities and durations of exercise. Because if you can nail this, then you can work your own nutrition plan out to figure out what you should be doing for fuelling sessions. So on the X axis, the line that goes across the bottom, the horizontal line across the bottom, here our intensity of exercise increases. So as a percentage of VO₂ max, we've got, say 25% VO₂ max which is the equivalent of sort of walking, very low intensity. And then the next bar up is 65% VO₂ max, and that's aerobic intensity. So it's kind of the intensity of going for a slow run. And then the next bar up is 85% VO₂ max. And that is more the intensity of our fast jogs or runs. And you know obviously 100% intensity is Max like you can't physically go any harder.

So as the intensity goes up, on the Y axis which is the one that goes vertical, our calorie burn per minute, is represented here. So at the low intensity of walking, we're burning a little bit of calories per minute, but it's relatively low. And then as we step up to aerobic intensity 65% VO₂ max, we burn way more calories per minute. You know, double compared to a walk. And then as the intensity goes up even further, we burn more calories per minute.

So I often hear a lot of people say, “Hey, I walk because it's better at fat burning.” We'll talk about that but yes, you are burning fat and a higher proportion of fat. But your overall calorie burn per minute is way lower than if you went for a run or jog. So it makes absolutely no sense to try and just walk for fat burning. You're so much better off going faster if you want to burn more calories because as the intensity goes up, we burn more calories per minute. Okay? So that's also important that you're going to burn more energy and need more energy intake, the higher the intensity of training session, and obviously the longer you're holding that high intensity pace for.

Each of those bars at those 3 different intensities is broken down into the type of fuel that we use during it. So like I said just before, walking at this low intensity, we're mostly burning plasma free fatty acids and they're the fats that are kicking around in your bloodstream. That's mostly what you use. We do burn a little bit of muscle triglycerides which is the fat that's stored in the muscle and a little bit of blood glucose as well. But mostly we're drawing on plasma free fatty acids – so fat.

Now as we step up to aerobic intensity, so going for a slow, steady run, we're burning about 50% fat, 50% carbohydrate. And that's important to understand. Because when you're going for long, slow sessions, because you're relying relatively heavily on fat still, you don't need to fuel beforehand so aggressively because you won't be burning through your carbohydrate stores as quickly as if you're going for a hard session. Okay? So we're burning about 50% carbs 50% fat here.

And the main difference that happens when the intensity steps up, is we draw on way more carbohydrate. So we are still burning fat, but it's more difficult. So up here, it's called out anaerobic intensity. Anaerobic means there's not a lot of oxygen present. So think about when you're doing hard sessions, it's really hard to breathe. If I asked you a question, you could probably give me a one or two-word answer at this intensity. Compared to aerobic, we go for a run with our buddies, we've got plenty of oxygen available. So aero means you know oxygen available. And we need oxygen to oxidise fat. Oxidise means break down or burn. So at lower intensities, we have the ability to burn fat as a fuel source because we have oxygen there to do that. You know, you can have a conversation with your buddy when you're running. You can answer, like a few words strung together to a sentence depending on how fit you are or how slow you're going. But as we step up to anaerobic intensity, 85% VO₂ max or higher, where we lose the ability to breathe, and we don't have as much oxygen available, we lose our ability to oxidise fat as efficiently.

So up here we are still burning a little bit of fat but less than at aerobic intensity. And I'd argue similarly to walking as well. But we're drawing on a bit more of our muscle triglycerides here which is the fat that's stored right at the muscle where we use it as a fuel. But here the difference is we're drawing on way more muscle glycogen, so the carbohydrate we store in our muscle.

So that's really important to understand, are you with me? Have a look at the image in the show notes if you're a visual person or rewind and listen to this again. But at that higher intensity where we're drawing on way more muscle glycogen, it's really important that our pre-fuelling includes carbohydrates and we have topped up our glycogen stores before the session as well. And in sessions like these, then you might want to look at fuelling with some carbohydrate during training sessions as well. But we'll talk about that another day.

So definitely jump on to the show notes and check it out. I think it's a really useful visual. It's something I go through with all of my clients so that you can actually see what you're burning at different types of training intensity. And as we delve deeper into this podcast, I think it's good to have a really basic understanding of that science to start with. Because then we can build on that as we build our nutritional principles around it.

Okay, so in terms of fuelling different sessions. Obviously it depends on the type of the session that it is, you want to have a different strategy for, say, like a strength or gym session so that we can maximize our strength gains and muscle hypertrophy. So building muscle tissue. It doesn't necessarily mean you’re going to get swole or bulk. But you do need the amino acid building blocks to help with muscle recovery and repair. You would do something differently to those type of sessions versus say, a long, slow session, you should have a different strategy for that. Based on what we just talked about with the fuel use, like obviously, depending on how long it is, you could potentially do some of those sessions fasted. But there is definitely a cut off where we're starting to get into the realms of under fuelling, injury risk, illness risk, etc by doing long sessions fasted all the time. So you want to have a bit of strategy to your eating. Maybe depending on how long it is, what your body composition goals are, where you are in your overall season. So I will do something different for somebodys pre-training in an offseason versus like peak race season as well. I think that's really important that you have that periodisation across your training year.

You want to do something different again, for a hard, interval type session. Because remember, we're drawing on way more muscle glycogen here, we're much more carbohydrate reliant at that higher intensity. So you want to have more carbohydrate available. And whether that looks like what you've done the night before or the day before. What you've done pre-training. What you do during - all that sort of stuff counts and helps when we are using much more carbohydrate in those high intensity type sessions.

And then you want to have a different strategy for say, an active recovery, passive type session. So those sessions could be fasted potentially depending on where you are in your season, depending on what your goals are, depending on what your body composition is at, what your injury profile risk is. So there's definitely no one size fits all with nutrition. And so, if pre-training is an area that you really struggle with, I'd encourage you to try and join us inside the Triathlon Nutrition Academy. Head to dietitianapproved.com/academy to check it out and either join the waitlist or come on in if the doors are open.

Because what I'll do is I go through with my athletes specifically, what they need to do for their different types of training sessions. They've got a different strategy for strength, a different strategy for those high-intensity, interval sessions. They've got a different strategy for the long sessions depending on how long they are. And then those active recovery sessions as well with specific foods based on their overall goals and where they are in their season. Because I take into consideration all of those little things. I don't think there's a one size fits all approach with nutrition. In fact, there isn't and there shouldn't be. But come on in and you can learn exactly what you need to be doing specifically for you.

Alright, that's it for today. Don't be the type of athlete that just trains fasted all week and also don't be the type of athlete that just eats the same thing every day. Try and build some structure and some strategy to really maximize your pre-training nutrition and set your whole day up on the right foot. And that way, you're going to make sure you're going to smash training, perform at your best and feel like a supercharged triathlete.

Because what's the point of under fuelling sessions? You're not going to get the most out of it and you're just wasting your time. And what's the point of eating the wrong things? Things that don't work for you, that don't sit well and you're always constantly stressed about where the toilets are or if you're going to have to stop halfway through a session and maybe not make it. You’ve spent all these hours training but if you haven't got your nutrition optimised, then you're not reaching your potential as a triathlete.

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