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Are There Benefits to Carbohydrate Manipulation? With Dr. Asker Jeukendrup

We sit down with sports nutrition expert Asker Jeukendrup to discuss potential performance gains from modifying carbohydrate load during training.

carbohydrate manipulation banana almonds
Photo: Merve Sehirli on Unsplash

It wasn’t long ago that most athletes, in the grand scheme of training, neglected the importance of nutrition, instead prioritizing time spent on the bike.  

Now, nutritional periodization and other methods of manipulation are rapidly rising in popularity. Many people strongly believe that significant performance gains are being left on the table if they neglect nutritional manipulation.  

Today, we sit down with one of the top sports nutrition experts to discuss the potential performance gains from modifying the amount of carbohydrate made available at a given time relative to training load. 

What are the benefits of low and high carbohydrate consumption and manipulation? What are the potential dangers? We’ll explain four distinct approaches:  

  • First, we’ll talk about the fasted workout—easily done by skipping breakfast.  
  • Second, we’ll discuss two-a-day workouts to reduce muscle glycogen. 
  • Third, we’ll consider low-carbohydrate diets. 
  • And, finally, we’ll dissect so-called “train-high, sleep-low” approaches in which an athlete will intentionally skip the recovery meal after a hard workout in order to ride the next morning under low carbohydrate conditions. 

Our leading expert, who returns to Fast Talk, is Dr. Asker Jeukendrup, known for his work with many elite athletes, in particular the cyclists of the Jumbo-Visma WorldTour team, and the Dutch Olympic Federation. 

We’ll also hear from a host of other great coaches and researchers, including Dr. Brian Carson, Joe Friel, Jim Rutberg, and Sondre Skarli. 

Put that bag of popcorn down! Let’s make you fast! 

For more on nutritional periodization, check out Fast Talk, episode 23: How Periodization Works for Your Nutrition.


Andrade‐Souza, V. A., Ghiarone, T., Sansonio, A., Silva, K. A. S., Tomazini, F., Arcoverde, L., … Lima‐Silva, A. E. (2020). Exercise twice‐a‐day potentiates markers of mitochondrial biogenesis in men. The FASEB Journal, 34(1), 1602–1619. Retrieved from

Areta, J. L., Iraki, J., Owens, D. J., Joanisse, S., Philp, A., Morton, J. P., & Hallén, J. (2020). Achieving energy balance with a high‐fat meal does not enhance skeletal muscle adaptation and impairs glycaemic response in a sleep‐low training model. Experimental Physiology, 105(10), 1778–1791. Retrieved from

Bartlett, J. D., Hawley, J. A., & Morton, J. P. (2014). Carbohydrate availability and exercise training adaptation: Too much of a good thing? European Journal of Sport Science, 15(1), 3–12. Retrieved from

Burke, L. M., Ross, M. L., Garvican‐Lewis, L. A., Welvaert, M., Heikura, I. A., Forbes, S. G., … Hawley, J. A. (2017). Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. The Journal of Physiology, 595(9), 2785–2807. Retrieved from

GEJL, K. D., THAMS, L. B., HANSEN, M., ROKKEDAL-LAUSCH, T., PLOMGAARD, P., NYBO, L., … ØRTENBLAD, N. (2017). No Superior Adaptations to Carbohydrate Periodization in Elite Endurance Athletes. Medicine & Science in Sports & Exercise, 49(12), 2486–2497. Retrieved from

Gensous, N., Bacalini, M. G., Franceschi, C., Meskers, C. G. M., Maier, A. B., & Garagnani, P. (2019). Age-Related DNA Methylation Changes: Potential Impact on Skeletal Muscle Aging in Humans. Frontiers in Physiology, 10, 996. Retrieved from

Hawley, J. A., & Burke, L. M. (2010). Carbohydrate Availability and Training Adaptation. Exercise and Sport Sciences Reviews, 38(4), 152–160. Retrieved from

Hawley, J. A., & Leckey, J. J. (2015). Carbohydrate Dependence During Prolonged, Intense Endurance Exercise. Sports Medicine, 45(Suppl 1), 5–12. Retrieved from

Impey, S. G., Hearris, M. A., Hammond, K. M., Bartlett, J. D., Louis, J., Close, G. L., & Morton, J. P. (2018). Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis. Sports Medicine, 48(5), 1031–1048. Retrieved from

Jeukendrup, A. E. (2017). Periodized Nutrition for Athletes. Sports Medicine, 47(Suppl 1), 51–63. Retrieved from

Lane, S. C., Camera, D. M., Lassiter, D. G., Areta, J. L., Bird, S. R., Yeo, W. K., … Hawley, J. A. (2015). Effects of sleeping with reduced carbohydrate availability on acute training responses. Journal of Applied Physiology, 119(6), 643–655. Retrieved from

Larsen, M. S., Holm, L., Svart, M. V., Hjelholt, A. J., Bengtsen, M. B., Dollerup, O. L., … Hansen, M. (2020). Effects of protein intake prior to carbohydrate-restricted endurance exercise: a randomized crossover trial. Journal of the International Society of Sports Nutrition, 17(1), 7. Retrieved from

Louis, J., Marquet, L.-A., Tiollier, E., Bermon, S., Hausswirth, C., & Brisswalter, J. (2016). The impact of sleeping with reduced glycogen stores on immunity and sleep in triathletes. European Journal of Applied Physiology, 116(10), 1941–1954. Retrieved from

Riis, S., Møller, A. B., Dollerup, O., Høffner, L., Jessen, N., & Madsen, K. (2019). Acute and sustained effects of a periodized carbohydrate intake using the sleep‐low model in endurance‐trained males. Scandinavian Journal of Medicine & Science in Sports, 29(12), 1866–1880. Retrieved from

Svendsen, I. S., Killer, S. C., Carter, J. M., Randell, R. K., Jeukendrup, A. E., & Gleeson, M. (2016). Impact of intensified training and carbohydrate supplementation on immunity and markers of overreaching in highly trained cyclists. European Journal of Applied Physiology, 116(5), 867–877. Retrieved from

Waterworth, S. P., Spencer, C. C., Porter, A. L., & Morton, J. P. (2020). Perception of Carbohydrate Availability Augments High-Intensity Intermittent Exercise Capacity Under Sleep-Low, Train-Low Conditions. International Journal of Sport Nutrition and Exercise Metabolism, 30(2), 105–111. Retrieved from

Yeo, W. K., Paton, C. D., Garnham, A. P., Burke, L. M., Carey, A. L., & Hawley, J. A. (2008). Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens. Journal of Applied Physiology, 105(5), 1462–1470. Retrieved from

Episode Transcript

Chris Case 00:00
Hey everyone, welcome to Fast Talk your source for the science of endurance. I’m your host, Chris Case.

Chris Case 00:18
It was long ago that most athletes in the grand scheme of training, neglected the importance of nutrition. Prioritizing, instead, time spent on the bike. But now nutritional periodization and other methods of manipulation are rapidly rising in popularity. Many people strongly believe that significant performance gains are being left on the table if they neglect nutritional manipulation.

Chris Case 00:45
Today, we sit down with one of the top sports nutrition experts to discuss the potential performance gains from modifying the amount of carbohydrate made available at any given time relative to training load. What are the benefits of low and high carbohydrate consumption and manipulation? What are the potential dangers? We’ll explain four distinct approaches.

Chris Case 01:07
First, we’ll talk about the fasted workout easily done by skipping breakfast. Second, we’ll discuss two-a-day workouts to reduce muscle glycogen. Third, we’ll consider low carbohydrate diets. And finally, we’ll dissect so called “train high, sleep low” approaches in which an athlete will intentionally skip the recovery meal after a hard workout in order to ride the next morning under low carbohydrate conditions.

Chris Case 01:35
The leading expert I mentioned earlier, who returns to Fast Talk for a second time is Dr. Asker Jukendrup known for his work with many elite athletes, in particular, the cyclists of the Jumbo-Visma WorldTour team and the Dutch Olympic Federation.

Chris Case 01:51
We’ll also hear today from a host of other great coaches and researchers including Dr. Brian Carson, Joe Friel, Jim Rutberg, and Sondre Skarli.

Chris Case 02:00
Put that bag of popcorn down! Let’s make fast.

Chris Case 02:06
Hey there listeners! You can join the smartest online forum in cycling for free. We’ve opened our podcasts forum to all members of Fast Talk Laboratories, so you can discuss recent episodes, ask follow up questions, and even chat with some of our episode guests. Join the conversation. Sign up now at

Chris Case 02:31
Well, welcome back to Fast Talk Dr. Jukendrup. It’s been years since we’ve had you on the program. It’s a pleasure.

Asker Jeukendrup 02:38
Yeah, it’s a pleasure to be back. Thanks for having me.


What is nutritional periodization

Chris Case 02:40
Absolutely. Today, we want to talk to you specifically about one of these periodization strategies for nutrition. We get a lot of questions about this particular topic in nutrition generally. So we want to dive into this with you today. Could we maybe start with a broad overview of what nutritional periodization is?

Asker Jeukendrup 03:07
Yeah, I think it’s really important to start there because I see the term used everywhere. And it is indeed very popular. But then if you dive into like different articles that you read, you notice that people actually use it in many different ways. So defining, what we are actually talking about is really important.

Asker Jeukendrup 03:29
So we made this the topic of a paper a few years ago to actually define what we mean by nutritional periodization. And the bottom line of the conclusion of the definition that we used was that when we talk about periodizing our nutrition, we are actually planning our nutrition. That is maybe one of the biggest changes. So instead of just eating or eating for recovery, we’re actually thinking a little bit further. What are we going to eat sort of this week? What are we going to eat before that training session? So there’s a lot of planning and that’s part of what periodization means.

Asker Jeukendrup 04:14
So there’s usually a longer term goal that you’re trying to influence and improve. So that goal, in the end, it’s always a performance goal, but it could be a shorter term goal that is like let’s try and improve fat metabolism, for example and let’s try to develop a strategy around that in this particular training session where we’re going to do this, this, this and this. So that is nutritional periodization. You think ahead of time, not just what your training is going to look like but also what your nutrition before during and after that training is going to look like.

Asker Jeukendrup 04:54
Periodized nutrition usually focuses on the muscle and adaptation in the muscle, but it could actually be much more than that. So we also wrote a paper about training the gut. So in that case, you’re not training the muscle, but you’re actually training the intestinal system to tolerate drinks or carbohydrate drinks better, or to absorb more carbohydrate. So it’s not just the muscle. But there’s also other organs such as the gut, then the brain that we can train through periodized nutrition. That’s also why it’s not surprising maybe that people get confused a little bit about what it actually means. It’s a very generic term that is used for a lot of different techniques that we can use.

Trevor Connor 05:47
What really caught my attention going back through the research is, you wrote a review in 2017, Dr. Holly wrote a review I think it was 2014 or 2015, I don’t have the date in front of me, but both of you said the same thing; which is basically that the progressive overload approach is no longer adequate. That we need to incorporate this nutritional periodization to get athletes to their best. And I think, and I would love to hear you talk about this, but I’m just going to start by saying, I think that’s a somewhat recent change in training. To give an example, I remember listening to a podcast with Floyd Landis, where he was asked about his nutrition and his comment was, “Oh, we ate like, crap. We all ate crap. That’s part of the reason we need to dope.” It seems like that has shifted that now there is this understanding that nutrition makes a difference. Nutrition is important, that’s going to raise our performance levels. And we really need to address this.

Asker Jeukendrup 06:48
Yeah, I see this as well. It’s definitely the last sort of three, four, maybe five years that you see athletes pay more and more attention to the nutrition in relation to the their training than just like it’s all about training – which it has been for many, many years. I think where a lot of people still struggle is like, “Well, how do you do this?” And I think, to be fair, a lot of scientists also still struggle there to sort of summarize the findings of the literature and turn that into real, like, easy to follow practical recommendations.

Trevor Connor 07:25
So let’s start with in both of those reviews, you and Dr. Holly, basically stated the same thing in terms of what is the goal that we’re trying to achieve here. And when you’re talking about training adaptations, you talked about it as gene expression, he talked about his protein synthesis, but we’re basically talking about the same thing. And this seems to be one of the key targets of this nutritional periodization. Is that correct?

Asker Jeukendrup 07:51
Yeah, I think that is correct. And it’s like, if you look at it from a historical point of view, I guess we go maybe back 100 years ago, if you wanted to test the effects of training, for example, the tool you had for that was a stopwatch where you would measure performance before and after a 10 week training program. And if you are faster, then obviously the training had worked. So then we got tools like heartrate monitors, and we could actually see maybe already after two or three weeks that our heart rates running at the same base would be lower. And so we were doing these physiology measurements. Then sort of the techniques further improved and we were able to measure things in muscle, like through muscle biopsies, for example, that gave us ideas on substrates that were being used. And then the techniques developed further and we started to look not just at muscle, but actually in cells and cellular processes. And much later, we also were able to look at molecular processes and even like DNA and everything. The more you look at that, like tiny detail from cells to molecules, the faster the responses are. Like a few minutes of exercise huge sea changes at the molecular level, that later are going to affect the cell, the organs and the training adaptation and ultimately performance. But in order to see the performance effects, you have to wait a long time. You have to get have to get a lot of these sort of signals in the muscle, right? And you have to accumulate these tiny little small effects over time to see a significant physiological and performance effect. So I think that’s what’s happened over time. Whether you talk about gene expression or whether you’re talking about protein synthesis, you’re just talking about slightly different processes in that larger process to training adaptation. And the more moleculur or the smaller you look, the faster the changes are going to be. But also the more uncertain that that small change that you see actually translates into something that is relevant to performance, if that makes sense?

Trevor Connor 10:27
Yep. So I’m looking at a diagram right now out of actually a 2018 review. That is a good summary of what I saw in your research and Dr. Hollys, and several these studies that it seems the the two pathways that get hit by these different approaches that we’re about to talk about are the one hand the ANPK, the other hand, the P38 MAPK – getting in some big terms here…

Trevor Connor 10:54
One we love on the show –

Chris Case 10:56
PGC one alpha

Trevor Connor 10:57
Chris wants to make a cycling jersey that just PGC one alpha

Chris Case 11:00
Yeah, absolutely, absolutely.

Trevor Connor 11:03
So it all ultimately leads to a ramp up in PGC one alpha, which leads to many of the adaptations we want to see for endurance athletes. But I gusee the question, and we’re gonna dive deeper into this is, certainly there’s been evidence that we see a ramp up of this activity, does it always lead to performance benefits?

Asker Jeukendrup 11:24
Yeah. And that’s a really good question that I think I answered very briefly by saying, if you measure those things really early on, it doesn’t always mean that you also get the performance benefits. But we don’t really have many studies. So there’s a lot of studies that look at the gene effects because they are relatively easy to measure, and they’re quick. But yeah, it doesn’t mean that you’re going to get a physiological adaptation doesn’t even mean that you’re going to get more protein, which you need to get before you get a physiological adaptation. And even if you get the physiological adaptation is that enough to get a performance benefit?

Asker Jeukendrup 12:09
The problem with the performance studies is they they’re, they’re really difficult to do. So I admire any researcher who does those sorts of studies, because you need to control all of the training of individuals, you need to control their diet, you need to control whatever else they do during the day, at least to some degree. And you need to do this for a very long time, because you’re not going to get measurable training effects in two or three weeks. So you need to do long term studies and control everything in the life of these individuals. So they are incredibly difficult studies to do. So, it is also not surprising, therefore, that we don’t have many of those studies.

Asker Jeukendrup 12:57
What is easy to do is, is do these short term studies and then sort of extrapolate, right?And that is what you see a lot in the literature. There’s a lot of hopeful extrapolation going on. So we see small changes. And yeah, maybe that could be beneficial. But yeah, it’s really difficult to say because it may just not be.

Trevor Connor 13:22
My master’s was a dual degree in nutrition and exercise bioenergetics. And when I was over in the nutrition department, I would listen to the nutrition students complain about how hard it is to get subjects to stick to the diet. And in the exercise physiology department, I would listen to people complaining about how hard it was to get athletes or people to do the exercises. And you’d have to get them into the lab and exercise in front of you to make sure they performed it. So the idea of taking those two issues and bringing them both into a single study and saying let’s do it over a long term. Just sounds like a nightmare.

Asker Jeukendrup 14:00
Yeah, it is a nightmare. And therefore usually they get truncated a little bit. So one example, there is actually a study that John Holly and I started at the at the same time. And the idea was to do half of the subjects at the University of Birmingham in the UK and half of the subjects in Australia. So I would do some of them, he would do some of them and then we put all that data together and turn it into a publication. For various reasons these studies never got combined, but there are two studies in the literature that are performed with exactly the same protocol and actually, if you look it up, the findings are also identical. So same protocol, same types of subjects. And in that study, we did do some of the short term measurements, we also looked at sort of the real – the the effects on fat metabolism, for example, and then we also measured performance. We had the same results in those two studies and that we did see, like the acute changes. And they were very clear. We did see changes in fat metabolism, but we didn’t probably because the study was only three weeks, we didn’t see changes in performance, but three weeks was really the maximum that we could do to control everything that we controled in those studies.

Trevor Connor 15:34
Three weeks is a shorter time to see any sort of performance gains

Asker Jeukendrup 15:37
It’s a very short time. Yeah, yeah. And any athlete knows that. It’s hard to get any real meaningful improvements if you’re already trained in three weeks.

High carbohydrate diets

Chris Case 15:48
All right, let’s shift gears a little bit talk about the carbohydrates here. This idea that there are a double edged sword, you need them, but they might, quote unquote, “hurt” training in some ways. Dr. Jukendrup would you like to take us away into the world of carbohydrates for a moment?

When do you need carbohydrates?

Asker Jeukendrup 16:09
Yeah, well, you need them in certain situations, I think. And those situations are when the intensity is really high, when performance is really important. I think, in the vast majority of sports, and also endurance events, carbohydrate is pretty essential. But on the other hand, if you’re training and your goal is not to perform at your best, because that’s not the goal of every training session, of course, then they’re not so essential. And so I, I see them as yes, they can support certain types of training, but I wouldn’t see them as essential for all training. They are essential for performance for sure.

Trevor Connor 16:56
So we’ve actually had Dr. Holly on the show, where he talked about that research he did in about 2015 or 2016 showing that when athletes ate a high fat, I don’t think it was a keto diet, but it was a high fat, very low carbohydrate diet, they really struggled at high intensities, because you actually saw a breakdown of glycolysis.

Asker Jeukendrup 17:20
Yeah, and this is the tricky thing. It works both ways. So if you have a diet that is very high in carbohydrates, you become very good at using carbohydrates. On the other hand, if you have a diet that is very high in fat and very low in carbohydrates, you become very good at using fat as a fuel. But the downside is that with a high carbohydrate diet, if you do that all the time, you become like really poor at burning fat as a fuel. If you’re on a high fat diet all the time, you become really poor at using carbohydrates as a fuel. And you can also measure why that is the case. There is a really nice study by John Hawley and Trans Sterlingworth I think, who did the study that showed that by ruva dehydrogenase is downregulated significantly when you’re on a high fat, low carbohydrate diet. And that is the key enzyme in carbohydrate metabolism. So if you down regulate that then even when you want to you just cannot use the carbohydrate. The other way around it also works. So if you always eating a high carbohydrate diet and always make sure that you have carbohydrate during your training, then you will become pretty poor at using fat as a fuel and you become very dependent on carbohydrate.

Trevor Connor 18:53
I’m really glad you brought that up because you think back – so there’s that whole glycogen loading belief that’s been part of sports for a long time. I meand that came out of the 1960s when they started doing muscle biopsies. And I think back to the research that even Dr. Schurman in the 1980s who showed that yes, you do this carb loading you can go into a race with higher glycogen stores. But exactly like you say, you become more reliant on that for fuel and even demonstrated that that could hurt performance.

Asker Jeukendrup 19:26
I’m not convinced that they would hurt performance but definitely you are more dependent on carbohydrate and therefore you use your stores faster. So you may have larger stores but you use them faster. So in the end, maybe the benefits are not as great as predicted.

Trevor Connor 19:46
Well, that’s what they were showing was that certainly in studies where they were looking to time to exhaustion, the people with the higher stock glycogen were actually reaching exhaustion sooner because they were so reliant on carbohydrates, they’re burning through it fast.

Asker Jeukendrup 20:00
Yeah, so it probably just stresses the importance of not just training one metabolic system, but making sure that all of it is trained, right?

Benefits of consuming carbohydrates

Trevor Connor 20:10
We’ve talked about benefits of carbohydrate, some of that being, it allows you, obviously, to perform better at high intensity moments in races. Certainly, there’s been a lot of studies, including yours that show that if you’re doing hard training, you can perform the training better with adequate carbohydrate stores. Are there other benefits to manipulating carbohydrates towards making sure you’re consuming enough or more than enough?

Asker Jeukendrup 20:44
Yeah, I think there’s one really important benefit and that relates to carbohydrate intake during training. Because I think most people, probably everyone, agrees that some form of carbohydrate intake during your racing, during competition, is important, and it will help performance. I mean, there’s so many studies that show that So, everyone has a strategy to dig onboard carbohydrates during their events. And now, if you haven’t practiced that and you’re trying to take carbohydrates at pretty high intakes, we’ve suggested and also shown in some studies that actually higher intakes will be beneficial. So the more you can push that carbohydrate intake, the more you can expect a positive effect unless you cause gi problems unless you cannot actually use that carbohydrate.

Asker Jeukendrup 21:44
So the other benefit of carbohydrate intake, taking carbohydrate during the training, is that you adapt the guts and you adapt the intestines to absorb more carbohydrate deliver more carbohydrate to the muscle and that will help performance.

Trevor Connor 22:01
When we had you on the show before. That’s exactly what you were talking about was training the guts so that you can handle a greater carbohydrate intake during events.

Chris Case 22:09
Yeah, and for those out there listening that want to refer back to that episode. It’s Episode 83: Training the gut with Asker Jukendrup.

Trevor Connor 22:18
And of course, my response is if you eat Swedish Fish, you don’t have to train your gut at all. Swedish fish will never do you wrong.

Chris Case 22:24
Never do you wrong, just swim around in there, and it’s like a massage to the gut. Nothing wrong could ever happen.

Trevor Connor 22:31
Sorry, I have a bit of a Swedish Fish obsession.

Chris Case 22:34
Do you know what Swedish Fish are, Dr. Jukendrup?

Asker Jeukendrup 22:36
I know from that episode.

Trevor Connor 22:40
Did we bring it up in that episode too?

Chris Case 22:41
Good memory, I’m sure we did.

Trevor Connor 22:43
I think we have used up all of our credits for Swedish Fish jokes. I think we have to stop those now.

Chris Case 22:50
Maybe on our jersey, it should say PGC one alpha and then the Swedish logo on there too?

Trevor Connor 22:57
People asked us if they sponsor us and we’re like, “Well, we’ve never talked to them. But we sponsor them.”

Chris Case 23:02
We kept the business alive by buying their product, let’s put it that way.

Does carbohydrates aid recovery and immunity?

Trevor Connor 23:07
So the last question I have is there’s some belief that making sure you’re getting adequate carbohydrates, even during training, aids recovery, and also helps immune function, what’s your feeling about that?

Asker Jeukendrup 23:23
What you do see is like recovery is poorer if you don’t have the carbohydrate, which is fine, if you’re still able to balance recovery and training on a weekly basis. But if you put too much of the sort of low carb training into your plan, it can become really hard to do the high intensity training because you’re just too tired to do it. So that’s one reason to make sure that you at least balance the two types of training: the low carb and the high carb training, you balance them really well.

Asker Jeukendrup 24:06
There’s also some evidence that low carbohydrate intake will cause more disturbances in immune function. Now, I have to say that a lot of those studies look at very isolated aspects of immune function. And there are very few – it’s a little bit like the acute measures mindset you can do in sort of signaling molecules, and genes and you can see changes early on, but it doesn’t necessarily translate into training effects – the same with the immune system. You can measure changes in the immune markers, it doesn’t necessarily mean that your immune system is really compromised and that you will get ill. So it’s the same sort of analogy, but I would agree that the risk of becoming ill is a little bit greater.

What are disadvantages of too many carbohydrates

Trevor Connor 25:00
So let’s flip this around. We said carbohydrates are a double edged sword. So what’s the issue with trying to consume a ton of carbohydrates in training?

Asker Jeukendrup 25:10
Well, I think the only issue that I can see is that you don’t get some of the benefits in, for example, developing your fat metabolism. So some of the signaling molecules that are necessary to improve your fat metabolism are blunted if you eat a lot of carbohydrates all of the time. And so that would be the downside because if those signaling molecules are reduced, you’re not going to get the same levels of gene expression, you’re not going to get the protein synthesis rates that you would get and after several weeks of doing this, you wouldn’t get the training adaptations that you would expect. So that would be I think, the downsides of taking carbohydrates all of the time.

Trevor Connor 26:03
Right, so going back, we gave the very brief overview of the signaling molecules and the one that seems to really be blunted by high carbohydrate consumptio is that a NPK?

Asker Jeukendrup 26:16
Yes, that’s one of the key markers for sure. You can also turn it around because AMPK is part of a glycogen molecule. And if you break down glycogen, then this AMPK becomes available. And if you have the glycogen stored, then the AMPK is not available. So if you’re glycogen deplete, you’re going to actually get higher levels of AMPK and that should really drive the training adaptation.

Fasted training techniques with Sondre Sklari

Trevor Connor 27:00
We asked Sondre Skarli, a former elite speedskater and now sports scientists at the Norwegian Olympic Committee, if he uses fasted training techniques with his athletes.

Sondre Sklari 27:10
No, actually, we haven’t done that. I’ve read some studies and articles about it showing some potential positive stuff, but then I think, as for elite athletes, that you don’t look so much at what can I gain in this workout or this workout, you have to look at the big picture, see on how those workouts fits together this week, this month, even this year. And sometimes you can do something that can be maybe good for improving this workout, but it’s not necessarily what’s big in the long term. It’s like having an epic high intensity workout where you really hit the wall, you do suffer harder than you’ve ever done, you do higher volume, you really crush yourself. And you can feel really good about yourself afterwards. But in the long term, maybe it was not the best thing to do because you have to look at the big picture. So I’ve been slightly afraid to do those kind of workouts with my athletes. Then again, I come from a sport with speedskating where we don’t need to focus that much on weight. These are athletes that it’s often 70, 80, 90 kilos guys, so they’re heavier than the cyclists. So we don’t focus too much on it.

Manipulating carbohydrate level to tap into training benefits

Chris Case 28:40
It sounds like for the most part, carbohydrate can be a good thing. But there are times when we want to limit it. I think it’s probably time we dove into that question a little bit. How are the different ways that you can manipulate your carbohydrate level to tap into some of the benefits you might see by training at a lower state.

Asker Jeukendrup 29:07
There are many different ways in which you can do this and studies have done it in different ways. And I think also athletes now use it in different ways. The most common way that I know is that people just go out without a breakfast in the in the morning. So in a way that is a form of carbohydrate restriction that can result in like different training adaptations. And there are quite a few studies that also like showed us that you can get at least some, or more of, of these signaling molecules and a little bit more gene expression of proteins that are related to fat metabolism.

Asker Jeukendrup 29:45
But all you’ve done, if you do that, is you have reduced your liver glycogen because overnight, the brain uses up some of the glycogen that is stored in the liver. Overnight nothing will happen with muscle glycogen because if you’ve eaten well, muscle glycogen stores will be full and they will not change. So you would start, like if you do this before breakfast, you would start with low level glycogen, but high muscle glycogen. And that gives different effects on certain genes.

Asker Jeukendrup 30:24
If you want to manipulate muscle glycogen, that is a little bit more complicated because when you manipulate that – well it’s easy to do you, you just exercise really hard and then after that, you have low muscle glycogen. But you can’t immediately do another session, then that’s the problem.

Asker Jeukendrup 30:45
So the way they address this in research studies was, the very first study was a really nice one, actually, they trained the left leg and the right leg differently. The right leg would train twice in one day. So the first time muscle glycogen was full at the start and the second time a little bit later in that day, muscle glycogen was empty. And then the left leg would train only once a day. So every day, the left leg would train once a day and the right leg would train twice a day, then have a day off. So their total training volume was the same. But what they saw is that the training adaptations in terms of fat metabolism, there were quite a bit greater in the right leg that had trained twice per day, and then had a day off. And that was attributed to the the fact that half the time that like had trained with low muscle glycogen. So when that study was published, my guy immediately commented and said, “well, it’s a bit of an artificial study, because what you’ve done is you’ve trained these two legs in exactly the same way. And that wouldn’t happen in reality.” In reality, if your muscle glycogen is full, you train harder. And if it’s empty, you train less hard. You don’t do the exact same training.

Asker Jeukendrup 32:23
So then this is when we started to look at sort of whole body exercises, a whole body training, to do a study with a training group and a control group where one of the groups would train every day, and the other group would train twice a day and then have a rest day. In the studies, we may be somewhat surprised at the time, we found pretty much the same thing. And the only difference was that the initial study that looked at right leg versus left leg had also found an effect on performance. And we didn’t see that effect on performance. But we only looked at three week duration of the of the training and aggression.

Trevor Connor 33:11
I read a really interesting review that dived into that issue with some of this research of if you are in a glycogen depleted state versus a glycogen replete state, you are going to train differently. And one of the things they theorized is basically any effective training is going to get you down to a certain threshold of glycogen depletion, that’s then going to activate many of these signaling pathways. And if you are in a replete state where your glycogen is full, you’re going to train harder, you’re going to train longer, but ultimately end up in a similar place.

Asker Jeukendrup 33:47
Exactly, that is also where my mind is. So yeah. Mm hmm.

Trevor Connor 33:52
So you’re feeling about the two days doesn’t seem to have that much of a benefit when you factor that in?

Asker Jeukendrup 34:00
No, I think when you factor that in, the differences become really small, and it’s much more difficult to measure. So I think, if you want to see these effects, you have to make these training sessions pretty extreme. So if you train low fat, then really train low fat. If you train low carb, then make it extreme. But then the challenge there is really to bring in enough recovery time.

Asker Jeukendrup 34:33
There’s the other factor, of course, because if you now have maybe a really effective training session that now requires twice the amount of recovery, have you really, like after a few weeks have you really gained much? Because you’ve also spent a lot less time actually training? There’s still there’s still a lot of questions out there that are unanswer to translate some of these, like theoretical findings that are quite clear to actually practical methods.

Trevor Connor 35:08
One of the first studies that I actually read getting ready for this podcast was one on a two-a-day approach by some researchers who seemed to be supportive of it. The title is “No superior adaptations to carbohydrate periodization in elite endurance athletes.” You know where this is going; they basically said, well, you just haven’t studied it for long enough. So they actually did this. They had two groups of elite athletes. So there’s triathletes and cyclists, one group – I believe their protocols are similar, but as as you said – one group is training every day, the other group was training every other day, but but doing two-a-days, and they did this for four weeks, and they really expected that you’re going to see much better gains in the two day group. At the end of that four weeks, both groups saw improvements, but it was exactly the same.

Asker Jeukendrup 35:54
It’s always difficult with these studies. If you don’t find an effect, it is always really difficult to conclude that there is no effect. There are two quite different things, I think. But what you can say is I think that the difference obviously, were, if they were there, they were fairly small and difficult to pick up. I think that that’s probably been the best conclusion. But I don’t think you can say from these sort of studies that are there is no effect.

Trevor Connor 36:26
Just hard to point out.

Asker Jeukendrup 36:28

High fat, low carbohydrate diets

Trevor Connor 36:30
So before we get to the sleep low approach, I think there’s one other that we need to talk about, which is the high fat, low carbohydrate diet. And so we can talk about it as keto or not keto, but basically eating a diet, that’s very low in carbohydrate. What has been seen in terms of that and performance?

Asker Jeukendrup 36:52
What is clear is that whatever diet you give to humans, l they will adapt to it. Some diets, you adapt very quickly, some diets like a high fat diet, it takes a little bit longer to really adapt to it. But ultimately, you will adapt to it, and you will be able to do similar types of things with a completely different fuel mix, that’s a fact.

Asker Jeukendrup 37:17
Now, if we then look at performance, then there are some things of physiology that do not change whether you’re adapted or not. If intensity is really high, you need glycolysis. That is just physiology, whether you can adapt for as many years as you like, you’re still if the intensity is high enough, you’re still gonna need glycolysis. With high intensity exercise, you’re still gonna need carbohydrate as the main fuel. So, this is why I think a diet or any diet that is the one solution for all problems doesn’t exist. A high carbohydrate diet is not a solution to all problems. A high fat diet or a keto diet is not a solution to all problems. And I think if you want to train your carbohydrate and your fat metabolism, because I think I read a lot about the keto diet and metabolic flexibility, well, you’re actually making your body very inflexible, because your body becomes really good at using fat and really poor at using carbohydrate. Same thing that would happen if you always were on a high carb diet, you’ll become pretty inflexible. We said earlier when you become very dependent on carbohydrates. So the the only way to stay sort of metabolically flexible is to give different challenges to the body at different times. And when it comes to training, we find this very normal, we find it very normal that we don’t train the same every day and we break up the training as much as we can, we give different stimuli. And I think we should do the same with nutrition. Not everyday the same. Some days, high carb, some days low carb and if you really want to get to the effects that we are talking about here, I think you have to really push this to two extremes sometimes, not every day, but sometimes.

Trevor Connor 39:27
I’m actually really glad to hear you say that because I agree. I don’t think for performance, a keto type approach, in the long term, is beneficial. But I also do think we we went a little too far with the “endurance athletes should be getting every carbohydrate they can possibly find in their system and you should be eating 700 grams per day” – I don’t think that’s necessarily beneficial either.

Asker Jeukendrup 39:54
No, no, it’s not. Of course of the two methods, it is probably the lower risk method that’s for sure, but I still don’t think that there is one diet that is suitable for all situations.

Dangers of fasted training with Dr. Brian Carson

Trevor Connor 40:11
We asked Dr. Brian Carson a leading expert on the effects of exercising in a fasted state, if he could see any potential dangers with fasted training.

Dr. Brian Carson 40:21
I think Dr. Holly’s group have some good publications and I think James Morton, who’s a practitioner at the coalface is involved in that research also, and he’s dealing with elite cyclists on an day to day basis. And so I wouldn’t have any major concerns about it, the evidence is strong, and it makes sense in that the hard session will be completed in a property fueled state. And so to maximize the the intention of that particular session, to be able to exercise at the right intensity at the right race speeds, and to be able to complete that session successfully. Then the recovery from that is maybe sub optimal from a carbohydrate perspective, as you outlined, perhaps you know there’s some protein and fats and maybe a low level of carbohydrate in the post exercise meal conducted that evening, the athlete sleeps overnight or sleeps low, and comes into the exercise session the following morning low in a fasted condition, low carbohydrate overnight and then exercises. But the intensity, and know this has been the case in those particular studies, the intensity is much lower, and probably below 60% Vo2max so you’re not potentially exposing the athlete to any dangers associated with maybe having low energy availability or low carbohydrate availability at that point in time and for that particular session, and it will be important to recover optimally from that session. So imagine the post exercise meal there would be high in carbohydrate, but it seems like a sensible strategy and have some good grounding in science.

Train-high, sleep-low approach

Chris Case 42:12
I’m not sure if this is one of the extreme approaches you are mentioning there Dr. Jukendrup but let’s get into the train-high, sleep-low approach. First let’s just describe tha,t talk about what that actually entails.

Asker Jeukendrup 42:28
Yeah, I think even here there are different versions of this, but typically you would have a normal day, you would not train until late in the evening, then you would not have a meal after that, you would go to bed, you would sleep, you’d wake up in the morning, and your breakfast would be very late. You would first train the next morning. So essentially, what we’ve done here is you put the training stress the day before, you make sure that all these signaling molecules are elevated, you make sure that there is no carbohydrate to blunt them and you make sure that these elevated signaling molecules actually can do their work for as long as possible by extending the next meal, making sure that the breakfast follows after the next training.

Asker Jeukendrup 43:28
So essentially, this is an extreme way, I think, to maximize these signaling responses. I should first say that this is not a method that I would use. But it does prove the principle for me that if you make it extreme enough, you’re going to get some pretty significant changes and signaling and protein synthesis and in training adaptations. Those studies are the only ones that really consistently show that this sort of approach can improve performance. And maybe that is just because it’s extreme enough to actually see these effects. The reason that I wouldn’t use it is, and this is personally or with my athletes, is that it’s maybe a little bit too extreme for me. I see that the risk of really disturbing sleep for me is pretty great and to risk of them needing so much recovery time is another one. I’m not convinced how practical this method is but it does really show to me that if you make these challenges, or the changes in your carbohydrate intake, if you if you really make them extreme you you are going to see some of these effects.

Trevor Connor 44:54
Really glad to hear you say that because that was going to be the first question I had for you. I have certainly had a few times where I’ve exercised late, not as much intentionally just because of other factors wasn’t able to eat or could only eat very little, and I know I can’t sleep that night.

Asker Jeukendrup 45:10
Yeah, it’s a common observation also with athletes that for whatever reason have to train late, there’s a lot of sports for various reasons, they have to train late, and usually they struggle to fall asleep. And I’m not sure if that’s really beneficial to the overall training response.

Trevor Connor 45:31
Now, I know there’s been some studies exploring those issues and looking at, well, what happens if you take a protein drink afterwards, at least you get some food in your system, but you’re still not consuming any carbohydrates? What’s your feeling about that?

Asker Jeukendrup 45:48
Yeah, and I think that that’s generally what studies have done, because like, given people absolutely nothing, I don’t think that would really help, I think the quality of the next training session would be so low that it becomes less meaningful. So most studies have done some feeding that just have avoided carbohydrate and I think it just depends a little bit on how much protein you give because protein also gives an insulin response so may blunt some of these effects. But the most important factor is to make sure that you don’t get the carbohydrate.

Asker Jeukendrup 46:32
I should make one other point about this sort of sleep low approach, because I see that some people associate that with a low carb approach, but it’s not really. It’s just, again, in those studies, the carbohydrate intake is the same in both conditions. So what are they? They train the normal way, or whether they use this more extreme approach, but the timing of the carbohydrate intake is different. So where the training is in the evening, the carbohydrate intake would be front loaded in that day. And if that training was performed in the afternoon, then they would have a meal after the training. But the overall carbohydrate intake would be the same induced to conditions.

Are there effective methods of carbohydrate manipulation

Trevor Connor 47:22
The question I have for you, we started by talking about nutritional periodization, and the values of it. We just talked about some of these carbohydrate manipulation strategies, and I didn’t hear a resounding “This is amazing! Why isn’t everybody doing this?” So I really want to throw that back to you and say, are there approaches that you do feel is effective? Or is this just a case of we still need to do research, as you pointed out, this research is very hard to do. Where do you stand on all this?

Asker Jeukendrup 48:01
Yeah. So, first of all, I would like to say that I do think that there is merit in this idea. But I also think that we don’t know enough, we don’t have enough research, to really come up with a clear recommendation that will work for everyone. It’s still a little bit sort of art at this moment while we’re figuring out the signs. So we have enough science, I think, to say this is a direction that that will work. But how we get this to work as effectively as possible that is still a big question mark.

Asker Jeukendrup 48:42
Then the second point I want to make is that we talk about this now as there is one approach for everyone. And I know for certain that people, if you give them the same sort of train low approach, they respond very differently in terms of how well they tolerate it, but also how much recovery time they need after it. And yeah, whether they feel good by doing it or not. So I think rather than having one sort of approach for everyone, maybe this is where we need to work much more on an individual level. And maybe there are people where we shouldn’t consider this at all, because it just doesn’t feel right for them and they just need too much recovery time. This is certainly something from working with professional cyclists that I have seen; there are riders that tolerate this sort of training really well and it’s almost like the more extreme you make it for them, the better they respond. And then there are other riders where this is the opposite and they really just cannot do it. This is another interesting topic for research because what makes those riders different? And maybe that will also give us clues to how to optimize these things, how to optimize it for different riders.

Chris Case 50:12
I got to think that pro riders also are an entirely different category then the majority of amateur riders. There’s significant differences there. And so the responses you would expect to be drastically different as well there.

Asker Jeukendrup 50:28
Yeah, absolutely. So, yeah. Also, you have to question whether these sort of methods are necessary for the vast majority of riders, right? These these methods are pretty sort of extreme and maybe a slightly less extreme approach is already enough for most people. But if we really want to find sort of the last little bits, I think these are tools that we should use and explore.

Jim Rutberg’s caution against carbohydrate manipulation

Trevor Connor 51:06
Jim Ruthberg, co-author of numerous cycling books, including “The Time Crunched Cyclists” and “Ride Inside”, had these words of caution when we asked him about the benefits of carbohydrate manipulation.

Jim Rutberg 51:18
One of the books that I was a co author of, “The Time Crunched Cyclists”, one of the things we were always concerned with was training the fundamentals versus training things that were more nuanced. And because people who have very little training time, they have a huge capacity, or usually have a huge capacity, for improvement within the fundamentals. And if they focus in on some of the very nuanced components of nutrition, or some other marginal gains type efforts, they’re often foregoing the larger gains that they can get simply by training, with higher quality in every workout that they do. So I guess my concern within nutrition, the carbohydrate availability manipulation, is would they be better off doing a higher power, higher effort, more high quality training session in that morning workout, then trying to accomplish something that is essentially going to be a fat oxidation manipulation? So the person who has the greatest capacity to benefit from the fundamentals, I’d say train with as much carbohydrate or as much energy availability as you can have, during those periods when you get to train.

Future research on carbohydrate manipulation

Trevor Connor 52:52
So what do you think is left to figure out in the research to help, as you said, it’s an individual thing, it’s gonna be very effective for some people, and not effective for other people, but we still need to do the research to figure out, okay, for this type of person, here’s a good approach for this type of person. That’s a bad approach. What do we still need to research?

Asker Jeukendrup 53:14
Yeah, so I think that’s identifyin – I mean, this would be really novel because there’s nothing in the literature, as far as I know, about individual responses to these types of training, or low carb training, for example. And so it would be really good to sort of characterize people and see, is there anything different? Because I think you can easily distinguish people in people who respond well, people who don’t. But what is different about those people? Those are questions that I would love to get answers to.

Asker Jeukendrup 53:50
I would also like to see more studies along the lines of the one we did that was like a little bit shorter, really short on these performance effects. So if people could do studies that go like to 7, 8, 9, 10 weeks even and then I would love to see what what are the actual performance effects? Rather than just looking at signaling, just looking at fat metabolism, what does it actually translate into? But as I said, those are super challenging studies.

Trevor Connor 54:26
And Chris also brought up a good point that I saw in several studies of addressing elite versus amateur athletes. And it seems like some of these strategies you actually see, even though this is an extreme that you would generally say only try this with somebody who’s really serious, it seems like you saw less benefit in elite and there were a couple explanations: One being that potentially these pathways AMPK, PGC one alpha, they’ve pretty much maximized the benefits from those. So ramping up that gene expression isn’t going to do much for them. Another explanation I saw was when they did glycogen analysis in elite athletes doing some of these carbohydrate manipulation studies, it was actually harder to get their glycogen levels down. Their ability to actually create, so gluconeogenesis, their ability to create carbohydrates was so good, they were actually keeping their glycogen levels pretty good. What’s your feeling on that?

Asker Jeukendrup 55:34
No, I exactly, 100% agree, apart from maybe the terminology. And then this is something that may be an interesting point to make because I come across this all the time. So we talked about the elite and then non elite, but really what we should be talking about is trained versus less trained. When we talk about elite, what we mean is these are the people who are training 30 hours a week, and they are super well conditioned. But I do know quite a few sort of, maybe we would classify them as recreational or maybe competitive athletes, they’re certainly not elite because they they don’t have the power outputs and they’re not at the same performance level. But they’re still training 25 hours a week, or maybe even 30 hours a week. And I think that is the more important factor. If we’re talking about someone who may be very talented and actually be like really close to the elite level, but is only training 10 hours a week, I think those are the people that can benefit from almost anything because they’ve never trained very much. And maybe the smallest intervention can have a very large effect, but if you’re already training 25 hours a week, it’s really hard to find something that gives you another 2%. So, in terms of terminology, I would always base it not so much on the performance level of athletes, but more on how much they actually train. How much they have conditioned their body.

Trevor Connor 57:20
Yeah. And also bring up somebody who’s training 25 hours a week and you’re pulling nutritional strategies that can impact recovery, you’re really playing with fire?

Asker Jeukendrup 57:30

Alternative periodization strategies of nutrition

Chris Case 57:32
All right, well, let’s close out by discussing any other periodisation strategies when it comes to nutrition that are out there. Are there things being developed? Do you see things that people are trying that might not even be in the literature yet that shows some promise?

Asker Jeukendrup 57:49
Yeah, there are. I mean, there are a number of different ways. People are trying to use supplements as well to support training adaptations longer term. And there are some studies, for example, with longer term bicarbonate use, fairly promising studies. But I don’t think it’s ready to roll out yet to the masses. So interesting ideas, but nothing that I would I would start to use.

What Dr. Asker Jeukendrup does with his athletes

Chris Case 58:27
Well, I guess the the question I’d like to ask is you talked about what you wouldn’t do with your athletes, what is it that you do with all these great athletes that you’re working with? Especially on the jJumbo-Visma WorldTour team, to get them where they’re at? And I know they’re very, very well trained athletes so this might not apply to our audience. But I’m just curious, if you’re willing to share, hopefully, they’re not proprietary or secretive in any way, you can share.

Asker Jeukendrup 58:58
Oh, no, no, I can definitely. So I think these approaches with train low, they are certainly being used, and they are used in certain phases of the season. So this is another thing that maybe we didn’t talk about. But when you’re trying to condition the body, and when you can make the biggest changes, this time of the year, or around sort of the December, January for professional cyclists, these are the times where they basically go from their lowest back to where they should be. So the improvements are relatively large. And this is where these techniques can really help and support. So training without breakfasts is a very common method. Training twice a day, a little bit less common, but it does happen as well. But there is also a very individual approach where like we don’t use all of these methods for all of the riders. There’s certainly some riders that do really well and over the years we’ve learned who responds really well and who doesn’t. So we individualize this approach very much. And so those are definitely things that we do.

Finding a nutrition periodization that works for you

Chris Case 1:00:18
For somebody out there listening that wants to try and find what might work for them, Does it come down to trying something, doing it for a long enough period of time and taking meticulous notes about how they respond? Is that what you would recommend for them? Or is there more to it than that?

Asker Jeukendrup 1:00:37
No, I think it is that and what I would recommend is, if you’ve never tried this, then go go out on a bike without without a breakfast. But don’t go on a really easy ride, which is like what a lot of people do, don’t go on an easy ride because an easy ride, you can tolerate anything. It’s it’s not challenging enough. So you need almost a threshold ride and do that in a fasted state before breakfast, and you’ll come back the first time and you’ll be shattered even. And maybe it was a short training session that didn’t work so well. If you repeat that one the week after, I almost guarantee that it will be better. And if you do it repeated again a week later, just do this once a week, you will see in just a few weeks time how much you improve.

Asker Jeukendrup 1:01:38
I’m sure it’s not all physiological adaptations that are happening here but it is a really interesting thing, little tasks that everyone can do, and I promise that you get some very interesting results from it.

Asker Jeukendrup 1:01:55
At the same time, what I would do is make one training session a week about the opposite. And make sure that you take in what you would take in a race, like pretty high carbohydrate intake, we sometimes recommend 90 grams or even more of carbohydrate per hour. Well, let’s try that on maybe the Saturday ride and make every Saturday ride about training high, training high carbohydrate. So those are two things that that I think people can try.

Joe Friel and carbohydrate manipulation variation in individuals

Trevor Connor 1:02:33
When it comes to attempting carbohydrate manipulation, take caution is the advice from renowned cycling coach Joe Friel. He cites differences in the evolution of digestive adaptation is one of the reasons people respond so differently when training in a low carbohydrate or a high carbohydrate state.

Joe Friel 1:02:52
It’s kind of sort of thing an athlete needs to get into gradually over time and not sort of the thing and introduce it the athlete does without having prepared for this in many ways, one way is simply to see what happens when we do an easy workout or a short workout after such a long, fast. Everybody’s different when it comes to the way their body responds to nutrition. If you’re working with an athlete who’s a American Indian descent, their way of dealing with their bodies operating differently than somebody who was from Northern Europe, in terms of carbohydrates; simply because, first, Northern Europe, their ancestors, you can go back many, many generations of eating high carbohydrate diets. They may have adapted to a very nicely, whereas the American Indian, Aborigines, Western African, and so forth, folks who are descended from those places are much less likely to have been involved in a high carbohydrate diet. So consequently, when you change the diet of a person, you’ve got to be very careful with doing it because we’re not all going to react the same way.

Joe Friel 1:04:12
And then there are the fact that some people eat high carbohydrate diets and other people eat high fat diet just as their normal way of eating. And that’s going to have an impact on this also. So it’s rather a complex situation to make a decision like this. But the thing to do with it from a coach’s perspective, or an athletes perspective, is to be very cautious at first so you don’t rush into something like this and immediately go out and do a four hour ride on an empty stomach having not had any intake since the night before have nothing with you on that ride, you’re just not going to be able to do that. You need to move into this very gradually over a long period of time, and begin to wean your body away from having carbohydrate intake right before a workout even during the workout. So it’s rather tricky and wouldn’t suggest most people try it unless they know something about what they’re getting into.

Trevor Connor 1:05:10
I also like the fact that you brought up timing is really important. Certainly in January is when I myself and with my athletes, I’ll say experiment with some things. This is the time of year when you’re out for a long ride and just noodling along. You’re gonna experiment a little bit with under consuming. I would never recommend this two weeks before a key race.

Chris Case 1:05:32
Yeah. I guess that is another question that comes to my mind. For those who are really sort of into the experimentation of training and all of that, and we have touched upon it here and there, maybe it’s a little bit amorphous and individualized. What can people expect come race day if they’ve done this? What does this mean for them if they’ve gone through this, if they’ve tolerated it? If they see “improvements” and how they respond for what you’ve just describe in threshold interval session, in a fasted state, or before breakfast? What happens in a race? What are the performance gains here that they might expect to see?

Asker Jeukendrup 1:06:25
Yeah, I think in a race, it’s really difficult to probably notice any difference because a race always feels hard, right? You go as hard as you can. So the way it feels is always going to be very similar whatever you’ve done. What changes is the speed at which things happen. So the performance changes, the way you feel not necessarily that much. With a training high and going in the other direction. I think that’s a little bit easier to answer because then you will be able to tolerate more. You will also have the confidence if you have done this in training many times you’ll have the confidence that you can tolerate more carbohydrate, and that that will in the end be beneficial because you can fuel your body better.

Take home messages

Chris Case 1:07:21
Well, we like to close out every episode of Fast Talk with our one minute take homes. We’ll start with you, Dr. Jeukendrup, in a minute, if you can, what is the most important message here for people to take home?

Asker Jeukendrup 1:07:36
Yeah, I think the most important message is that there is not one diet that fits all purposes. That’s what I would like to start with. So neither high carb nor high fat, that’s not a solution, I think the solution is in being or making your body metabolically flexible, which means sometimes high carb, sometimes low carb, and I think there are definitely some opportunities by training low carb in different ways, making the training quite extreme in a similar way that training really hard is going to give you more effect than than training at a moderate pace. And those would be the main take home messages. Plus maybe the fact that it is extremely individual and we know very little about what makes people so different.

Chris Case 1:08:35
Trevor, what would you add?

Trevor Connor 1:08:37
Really my big take home is I was very happy to hear you say this stuff is interesting, but there is no miracle cure here. And as a matter of fact, a lot of these strategies you wouldn’t use. We’ve been asked about it, so I know we have listeners who are hearing about these things and wanting to experiment with it and I get worried about somebody who has a family, has a job, getting on the trainer at 10 o’clock at night destroying themselves and then going to sleep, getting up at 5am to do their glycogen depleted ride and go I’m gonna have my best season ever! No; you could just as easily be completely overtrained by February. I like that you say there’s potential here. There are things that we can do. I hope you agree that’s still the main message is focus on eating well, training right, eating healthy, these are the best things you can do.

Asker Jeukendrup 1:09:31
I couldn’t agree more.

Chris Case 1:09:33
Yep, that’s what I would close with as well. We’ve spoken so many times on the show about it’s not about one macronutrient, it’s not about one type of diet, it’s about that blend of a lot of things. But all in all, eating really well, healthy, good foods is first and foremost what’s going to make you the best athlete and then these other things are potential bonus for certain people. But I would take a prudent approach; if it’s not for you don’t bother with it. If you’re into experimentation, probably take baby steps don’t just go full bore. So that’s what I would leave with.

Chris Case 1:10:17
Well, it’s been a pleasure. Dr. Jeukendrup, thank you again for coming on Fast Talk.

Asker Jeukendrup 1:10:21
Well, thank you. It was a pleasure.

Trevor Connor 1:10:23
Thank you.

Chris Case 1:10:27
That was another episode of Fast Talk. Subscribe to Fast Talk wherever you prefer to find your favorite podcasts. Be sure to leave us a rating and a review. The thoughts and opinions expressed on Fast Talk are those of the individual. As always, we love your feedback. Join the conversation at to discuss each and every episode. Become a member of Fast Talk Laboratories at and become a part of our education and coaching community. For Dr. Asker Jeukendrup, Dr. Brian Carson, Joe Friel, Jim Rutberg, Sondre Skarli, and Trevor Connor I’m Chris Case. Thanks for listening.