Episode 253 - Is Carb Loading a Myth?

Is carb loading a myth? A paper published in June has social media convinced that it is.

A comment landed on my socials this week saying exactly that. It didn't appear out of nowhere. There is a new paper doing the rounds, the headlines have picked it up and sprinted into some pretty heavy clickbait territory, and they have taken it somewhere I don't think the authors ever wanted it to go. So I'm going to tell you exactly what that paper says, what it doesn't say and how to apply it to you as an age group triathlete.

I'll walk you through the 14 studies this whole argument rests on, why only 2 of them were double blinded and the detail in the research design that changes how you should read every one of those headlines. Then I'll show you brand new data on 27 real women racing at the 2024 World Champs, which I think is the far more important number for you.

IN THIS EPISODE

• What the June 2026 commentary actually did, and why it is not the carb loading study everyone thinks it is
• How 10,422 papers were screened down to just 14
• Why most of that research doesn't reflect how you actually race
• What happened to muscle glycogen when athletes ate enough carbohydrate
• Why I never wrote Matt Hauser a carb loading plan, and what that tells you about yours
• The World Champs food diary data on what female age groupers really ate the day before their biggest race
• The second problem with this research that nobody is talking about yet
• What I want you to do differently before your next race

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Episode Transcription

Episode 253: Is Carb Loading a Myth?

Welcome to the Triathlon Nutrition Academy podcast. The show designed to serve you up evidence-based sports nutrition advice from the experts. Hi, I'm your host Taryn, Accredited Practicing Dietitian, Advanced Sports Dietitian and founder of Dietitian Approved. Listen as I break down the latest evidence to give you practical, easy-to-digest strategies to train hard, recover faster and perform at your best. You have so much potential, and I want to help you unlock that with the power of nutrition. Let's get into it.

[00:00:00] I have recently launched my Carbohydrate Loading Masterclass, and it has been really well-received. So thank you so much if you are one of the athletes that has purchased it. You can check it out at dietitianapproved.com/carb-loading if you're interested. But with that has come a lot of engagement on my social media posts lately, and one comment I received this week was, "Carb load is a myth."

[00:00:27] Now, that comment didn't appear out of nowhere. It wasn't completely left field. There is actually a new paper doing the rounds at the moment, published in June, and social media is having a field day. It has picked it up and sprinted with some pretty heavy clickbait territory and taken it somewhere that I don't think the authors ever really wanted it to go.

[00:00:46] So I'm going to tell you exactly what that paper says. We're going to dive into the details as always, and apply this to an age group triathlete in a practical sense. My name is Taryn if we haven't met yet. I'm an advanced sports dietitian and triathlon nutrition specialist, and I've spent two decades working with triathletes at both ends of the sports, from complete beginners doing their first race on a borrowed bike, all the way up to Kona winners, and for six years with our Australian elite triathlon team for Triathlon Australia.

[00:01:17] Is carb loading a myth? Let's dive in. So let's start with the paper that is causing all of these clickbait headlines because if you've seen all those headlines, you may not have actually seen the details and know about any of the nuance. And this is honestly one of my favourite things to do, to take the really complicated science and turn it into practical, easy-to-digest information that my grandma could understand.

[00:01:42] I will link it below if you do want to go read it for yourself. It was published in the International Journal of Sport Nutrition and Exercise Metabolism in June 2026. Now, it is a commentary. It is not a carbohydrate loading performance study. Nobody put anybody on a bike and made them ride 180 kilometres, so no new data was collected.

[00:02:04] But what they did do was go back through all of the existing carbohydrate loading research and provided their insights. Now, this is a great and really useful thing to do, particularly when we're talking about six decades or more of literature, and they screened over 10,000 papers. 10,422 papers. And they filtered down to studies that had an endurance performance test lasting greater than 90 minutes, comparing a normal, in inverted commas, carbohydrate intake of around four to six grams per kilo.

[00:02:38] Now, I would argue, as somebody that works with age group triathletes, that that is a high end of normal for an age grouper. And they compared that normal level of carbohydrate intake to a loading intake of carbohydrate above seven grams per kilo. The study period needed to run for at least 24 hours to be included.

[00:02:58] So out of 10,422 papers, that left them with 14 studies. 60 years of carb loading research and the evidence base for this commentary is now 14 papers, and only two of those 14 papers were double-blinded placebo control trials. So quick translation, double blind means that both the athletes and the research involved didn't know which arm of the study they were in.

[00:03:29] It is gold standard because if you know that you've carb loaded, you might just ride harder. It's called the placebo effect, and it is real. If you know you've carb loaded and you think you've got a fully loaded glycogen fuel tank, you can push harder whether you actually do or not. So only two studies were double blind.

[00:03:49] The other 12 studies, everyone knew exactly what they'd eaten, and blinding for carbohydrate is genuinely hard. It's not easy to sneak 600 grams plus of carbohydrate past somebody when you have to eat it. There are definitely ways. You could nasogastric feed somebody, where you stick a tube down their nose and feed them directly into their stomach. I love eating, and you could do it for science, but it wouldn't be my first preference.

[00:04:17] You could also sneak maltodextrin into food and use things like artificial sweeteners. So it's not impossible, it's just, like, impractical. Now, out of those 14 studies, only four of those studies actually gave the athletes some carbohydrate during their performance test, which means 10 of those studies, 71% of this commentary's endurance base, tested carb loading with zero exogenous fuel on board.

[00:04:41] So fuel coming in during exercise. And seven of those also tested the athletes fasted. So nothing to eat after their overnight fast. No breakfast, no pre-race meal, fasted. So they're riding for, you know, two hours, they don't have any fuel during, and for some of them they didn't have anything to eat before.

[00:05:00] So it's not particularly applicable to how we race as triathletes. And the four studies that did fuel their athletes during exercise gave them around 60 to 70 grams of carbs an hour, which back then was, you know, relatively good, relatively ambitious. But today, when athletes are fuelling, like, 120 grams of carbs an hour, kind of sits well below where we're at these days.

[00:05:25] Not that everyone's fuelling at 120 grams of carbs an hour. I have another **[episode on that](https://www.dietitianapproved.com/53)** if you do want to dive into that, and I'll link that below as well. I don't want to get sidetracked. Now, where this myth line has come from is that the two good studies, the ones that were double blinded, found nothing, in inverted commas.

[00:05:42] They showed on paper no performance benefit from carbohydrate loading, and that was Louise Burke's group in 2000 and Tomcik in 2018. There was no significant difference in their time trial time, as in a P value. No significant difference in power output, which is where these clickbait headings are coming from.

[00:06:03] Now, these were not bad studies. I'm not about to stand here and tell you that these world-class researchers got it wrong. Louise Burke was the head of nutrition at the AIS, the Australian Institute of Sport. She was my boss for a while there. She is one of the most respected sports dietitians on the planet.

[00:06:23] I have enormous respect for LB, so I'm not going to pull apart either of these studies or the methodology here. We'd be here for hours if I did that. If you drill into the details though, when carbohydrate intake is high enough, muscle glycogen levels did increase. The first paper took seven well-trained male cyclists, no females, gave them 9 grams per kilo of carbohydrate for three days versus a control group that only had six.

[00:06:51] They muscle biopsied them, so literally put holes in their quads. I think it was the vastus lateralis, so your quad muscle that sits on the outside, and their muscle glycogen went from 485 to 572 millimoles per kilo of dry mass. So an 18% increase, which is not to be sneezed at. That is a great increase in glycogen, but it's also not particularly high amounts of carbohydrate intake either.

[00:07:16] Then we have another paper where they fed them 6, 8 or 10 grams per kilo for 48 hours. They also took muscle biopsies. 6 grams gave them 461 millimoles per kilo of dry weight. 8 grams gave them 506, and statistically there is no difference between these two. The P value was one, but practically that is still an increase in muscle glycogen.

[00:07:40] Just because something is not statistically significant doesn't mean it's not practically significant. But the 10-gram-per-kilo group jumped to 636. So what that tells you is the earlier research probably didn't have enough carbohydrate to show a really good effect. When you increase it, then something meaningful happens.

[00:08:02] The Tomcik paper, which is one of those two double-blinded placebo-controlled trials that the commentary pulled out. They compared 12 grams of carbohydrate per kilo versus six grams per kilo, so a big gap there. And the group that had more carbohydrate had glycogen levels of 724. So these athletes are genuinely glycogen loaded.

[00:08:26] But the performance test that these guys had to do, poor bastards, was even more complicated than what Louise Burke made her athletes do. They had to do a 121-kilometre time trial on the bike with six four-kilometre sprints and six 1K sprints throughout it, and then a 10K hill climb with an 8% gradient ridden to exhaustion at 90% of VO2 max.

[00:08:50] That sounds bloody horrible. You complain about your FTP testing. Can you imagine doing that? But the thing is, this study was primarily a creatine study. Carb loading was just one variable sitting alongside creatine loading, with three different groups being compared. It was actually never designed as a carb loading study.

[00:09:09] So none of this so far proves that carb loading is a myth. What we've actually got is two studies. One is underdosed, it doesn't have enough carbohydrate to effectively carbohydrate load, and another whose authors flagged that their study designed that they cooked up may have masked the effect. They were both in well-trained cyclists, both in the lab.

[00:09:33] So I don't think, as a practitioner, this is a case closed. I think this is a case barely opened, and it opens up the door for future research to keep digging into this space and really try and finesse the details, which is so exciting. So that is why I'm not throwing carb loading in the bin over two studies.

[00:09:50] If I stop this episode right here, maybe you'd unfollow me, follow the clickbait headlines, and go and smash a big salad the night before your next 70.3. Please don't do that. Because even if both of these studies had been perfect, if they'd nailed the carbohydrate dose, if they'd nailed the blinding and the actual performance test within, I have a much bigger reason about why this research is not actually about you.

[00:10:15] It was in men, but it's also not what age group triathletes do. There is a beautiful paper that has just been published in a group of triathletes in women at the 2024 World Champs. I will link it below. I'm so excited for this. It was 27 real women, not lab rats, actual age group triathletes racing at World Champs and studied in the real world.

[00:10:40] They kept 48-hour food diaries in the lead up to their race. They were interviewed before and after, and these are real women that qualified for World Champs. They trained for years to get there. They flew across the world. They care about this event more than anyone else on the planet, and what they found was only 26% of them hit their carb loading guidelines, which means that nearly three-quarters completely missed it, and the average intake across the entire group was only 6.4 grams per kilo.

[00:11:12] The best female age group triathletes in the world on the day before the biggest race of their season, of their career, when they were actively trying to carbohydrate load only ate 6.4 grams per kilo. That is the control group in those previous studies that I talked about. These women were eating the amount that the other research called not carb loading on World Champs eve while believing and thinking that they were loading, and they did a correlation. The athletes that ate more carbohydrate raced faster.

[00:11:45] That was a statistically significant relationship in the data. Now, that is not correlation. It is not proof of cause. The women eating more carbohydrate might have had their shit together. Maybe they were more organised. Maybe they were across it. But it points us the same direction as everything else that I know about age group triathletes.

[00:12:03] The research papers are arguing about filling up your glycogen fuel tank. We're talking about, you know, filling up the top of the tank, whereas age groupers are still struggling just to fill it halfway, to fill it to a quarter of the tank. This is the single biggest pattern I see in age group triathletes all the time, and I say this with love, as somebody that's trying to help you.

[00:12:25] You have an elite athlete mindset. You train like a professional triathlete. You spend money on the bike, the watch, the coach, the training program, the power meter, the carbon fibre running shoes, and then you eat like a complete beginner. In 20 years of doing this, it's still the same story. Train like a professional, but your fuelling is amateur hour.

[00:12:48] Now, if I compare that to the elites, for six years, I was one of the dietitians that looked after our Australian elite triathlon team when I worked for Triathlon Australia, so Olympic-level athletes, the paratriathletes, and the developing athletes coming up in the pathway. Matt Hauser was one of the athletes that I looked after at that time.

[00:13:07] He has also been on the podcast if you do want to go and listen to his episode. Now, I never wrote Matt a carb-loading plan, not once, and that is not me doing my job poorly. He didn't need one. Matt already ate at carb-loading levels on a daily training basis. All he needed to do was keep eating normally and taper training, and he effectively carb-loaded.

[00:13:30] So what he needed from me was completely different to what an age group triathlete needs from me. He needed food choices, making sure it was easy for him to get to, because cooking at that age isn't a skill set they've developed particularly well yet. That was one of my jobs. Making sure it is gentle on his gut so that he can toe the start line and redline it for a couple of hours and know that nothing is going to go pear-shaped.

[00:13:55] Make sure it is familiar, it's easy, and it's well-practised. He already eats at a carb-loading ceiling, so my job was just to support everything else around that. So if I took an athlete already eating, like, top-level carbohydrate loading numbers on a daily basis and told them to carb-load, maybe then you could say carb loading is a myth.

[00:14:14] If they taper training, then their glycogen fuel tank should already be, like, relatively close to full, so we wouldn't see a statistically significant change in glycogen content if we biopsied their muscles. But I would argue that nobody listening to this right now is that athlete. Which brings me right back to where we started, that comment.

[00:14:34] So when I asked that person, like, "Says who? What do you mean by that?" They said that your muscles only store a finite amount of glycogen, and once those stores are full, more carbs won't keep increasing it. And they are absolutely right. That's correct physiology. There is a ceiling. More is not better. But it's a myth versus there's a ceiling that exists and your tank being full are two completely different statements.

[00:14:59] That's assuming the tank was already full, and for the women who fronted up to world champs in 2024 on only 6.4 grams per kilo carbohydrate, having trained their butts off for months, they're nowhere near that. And unfortunately, this is the same leap that the internet has made with this paper. So frustrating.

[00:15:18] And these studies found no extra benefit at the top of the tank when we're trying to get from 90% full to full, and social media has turned it into carb loading is a myth. So that's the first problem with applying this research to you. You are not the athlete that it studied. But there's a second problem, and one I think nobody's actually talking about yet.

[00:15:40] Because even if you are that athlete, even if you're eating really high amounts of carbohydrate on a regular training day, this is only talking about one parameter, and that is grams of carbohydrate. But carbohydrate loading done properly is not just carbohydrate alone. This is exactly why the calculator in my carb loading masterclass doesn't just give you your carbohydrate number.

[00:16:04] It actually gives you five. It gives you your carbohydrate, your protein, your fat, your fibre, and your overall energy, your calories or kilojoules for your loading days. If you nail your carbohydrate number and you get the other four wrong, you will feel bloated and heavy and flat on race morning, and you might come to the conclusion that carb loading doesn't work for you, that it's a myth.

[00:16:26] So does this change my advice? Short answer, no. Not yet. I think it's risk versus reward. You've spent months training for this race. There's been early mornings, plenty of sacrifices, maybe some missed social stuff. You've spent money on the bike, your coach, the entry, the flights, the accommodation, and there's maybe been a lot of sacrifice that's gone into it.

[00:16:49] Compare that to carb loading, it's a couple of days of eating deliberately. Done properly, it is safe, it is cheap compared to all those other things, and it's completely reversible. If it works, you protect months of training work. If it turns out it's doing less than we thought it was, hey, you've eaten some extra rice and you've put a bit of extra fuel in the tank.

[00:17:11] Like, there is nothing wrong with that. I think this is the easiest risk reward of our entire sport. One of the authors on this very paper, Jose, said very publicly that carb loading may work, carb loading may not work, but if it might work and it's not difficult to do, you'd be silly not to do it anyway until we know more.

[00:17:32] And on the placebo thing, let's just say the sceptics are right and part of the benefit is that belief that you are carb loaded. So what? If you stand on that start line feeling ready, confident, like you've done the work, and you race faster because of it, you just race faster. I'm not chasing a philosophically pure performance gain.

[00:17:54] I want you to cross that finish line with a smile on your face, no matter what. So what I actually want you to do, don't skip it. Nothing in this paper is reason to skip it. But start earlier than the day before race day. Start by looking at what you eat on a normal training day, because this, for a lot of age groupers, is where the gap is.

[00:18:13] If your everyday carbohydrate is too low, no amount of big bowl of pasta on a Saturday night is going to rescue you. Watch your fibre intake. Stick with familiar foods. Don't do anything weird. Practise it well before race week, because the number one rule of racing is never try anything new on race day. And if you're a female athlete, you need to understand your cycle and that it matters, and that hitting your numbers for you is even more important.

[00:18:42] So, phew. Are you still with me? Is carb loading a myth? No. But the way in which a lot of age groupers do it, look, that might be. Because the research is arguing about the top of the fuel tank, and a lot of age groupers are still trying to fill the bottom half. And importantly, carb loading is more than just a carbohydrate number.

[00:19:06] It is your carbohydrate, your protein, your fat, your fibre, and your total calories in food choices that you know are well-practised in a body that is uniquely yours. There is no one-size-fits-all to carb loading, okay? You are your own experiment. You need to understand your unique numbers and continually dial them in for you.

[00:19:25] If you want the whole thing properly laid out for you in an easy-to-understand way with a planner and calculator that does all of the hard maths for you, that gives you your five numbers, not just one, and the information about the female athlete and your menstrual cycle and how to apply this to you, my Carb Loading Masterclass is at dietitianapproved.com/carb-loading.

[00:19:49] Thank you for tuning in. I'll see you next week.

Thanks for joining me for this episode of the Triathlon Nutrition Academy podcast. I would love to hear from you. If you have any questions or want to share with me what you've learned, email me at [email protected]. You can also spread the word by leaving me a review and taking a screenshot of you listening to the show. Don't forget to tag me on social media, @dietitian.approved, so I can give you a shout out, too. If you want to learn more about what we do, head to dietitianapproved.com. And if you want to learn more about the Triathlon Nutrition Academy program, head to dietitianapproved.com/academy. Thanks for joining me and I look forward to helping you smashed in the fourth leg - nutrition!