this is spectacular explanation of N=1 experiments with lots of insights
so excellent data match with personal needs and intuitions, paying attention to how quality of life during day, sleep, performance, recovery look like in these month, adjusting for different training and... yess I think a bit of effort and courage to test something extremely new
I remember you telling me about the experiment you started back in February in Gran Canaria when we meet. I am super excited to see how diligent you were with this and the documentation, as well as the ability to share openly so many details about it. Thank you Marco and most likely I will reach out to you for few ideas I have with Kasia, but I need her to buy in. Hope to meet you soon! 🤙🚀 Abrazo fuerte y besos para Alessandra ⛰️🏃♂️🔥
I remember you telling me about the experiment you started back in February in Gran Canaria when we meet. I am super excited to see how diligent you were with this and the documentation, as well as the ability to share openly so many details about it. Thank you Marco and most likely I will reach out to you for few ideas I have with Kasia, but I need her to buy in. Hope to meet you soon! 🤙🚀 Abrazo fuerte y besos para Alessandra ⛰️🏃♂️🔥
I have done my own experimenting with precisely this type of nutrition some years ago (2017-2018). I didn't call it periodisation but "strategic use" of carbs :D. However, I had no access to the advanced measurement devices nor the scientific knowledge you obviously posses. What I was able to measure though, was the increase in fat oxidation while running the same pace after about 4 months of using similar nutrition protocol you describe. This was done in a professional sports lab, so really could see a change. The result was that I was able to sustain a given pace for much longer while consuming roughly the same amount of carbs per hour (about 45g). I ran ultras at the time (UTMB and such) so my goal was to get around the loop as fast as possible while being able to sustain fuelling for around 28-29 hours of racing. I had not much knowledge about HRV at the time so I did not measure it but your insights and the details you go into are fascinating and truly a goldmine for people like me. Thanks again!
Great article, as always. One reflection I had on your gastrointestinal issues: did/have you considered fermented foods as additions to meals and snacks and/or probiotics?
thank you. Definitely something to look into, I appreciate the input. For lower carb days, issues are basically resolved - something eventually I could pin down at least partially to gluten, as I do not have the same issues also when I reintroduce certain types of carbs that do not contain it - but on higher carb days or especially when I have a couple of days in which I have more and maybe I also have more ‘standard lower quality carbs’ (even just bread and pasta), it seems that I can have more problems. Work in progress.
Thank you so much for your work and sharing amazing insights and details. I am by myself aging recreational female athlete and I plan my second MDS next year. I have problems with carbs during training and was "dancing" with different ideas about nutrition. That said while modifying my diet so far I have los 6 kg (~4%fat). Now I am in the process of moving toward complex carbs, eliminating simple from diet. And as a next step I consider further periodization. BUT:) My main fear is about ramping up protein intake. As I have calculated from your data, you have about 2,5 grams per day. Is that OK from longterm health issues and did you check UREA levels in blood? I am very easy on protein and can take like 2,2 grams per kg per day, but try to limit to 2 gr. May be this is not as serious as I think. I have no answer for this so far.
thanks Nadya! I think recommendations for athletes are around 2g/kg, hence that's what we are currently advised to do. My numbers might have some errors (there are just estimates), and there can be days in which the intake is a bit higher, as there are days in which the intake is certainly lower (if I'm having more higher quality carbs or training less, there will be less protein). In my view an important aspect remains always the quality of the diet, the variety of protein sources, etc. - I think that if we make an effort to eat well, whole foods, etc. - it is unlikely that we are creating issues, I think (while there might be studies showing a very high protein intake is not recommended, these are unlikely to be in athletes and probably involve a diet in which protein might come almost exclusively from meat or red meat, as it seems to be common in certain groups). All the best for your training!
Perdonatemi per questo lungo commento, ma leggere e rileggere il vostro blog e ascoltare i podcast stimola davvero la mia piccola mente appassionata di sport!
- Again, congratulations for your dedication, navigating such diet changes in the pursuit of racing goals is purely amazing
- Was there a gradual cut of carbs before December/January or was it more direct process ?
- It would be nice to have the written percentages on the histograms of your macro distribution
- I would also be interested in knowing your energy expenditure at the pace you take for examples in your oxidation rates
- I see that you’re often very low in carbs (<50g) despite training everyday, that’s quite a challenge to go lower 50g of carbs. I guess you must cut off anything starchy and get your carbs from vegetables to stay this low. I will have to start a new love with broccoli if I go this way…
- I see AC back in 2008 having good results with an athlete with still quite a lot of carbs, of course everyone is different, but his strikes me : « I put this athlete on a diet of 400g of CHO/200g of (lean) Protein and 100g of (good) Fat. This represents 3300kcal/day and 48%/24%/28% macronutrient breakdown. Irrespective of whether the diet is eucaloric or not, I have found these percentages to be ideal in the base phase of training. » I have computed my macros this week and I was 39%/21%/39% and I feel like I have plenty of room in terms of fat oxidation (last time I measured I was 0.6 g/min at FatMax…)
- Also DP seems to have some divergent opinion from BS when writing « Remember that exercise duration is the most potent stimulant for fat oxidation; this is above specific macro-nutrient manipulation. » So my remark is that your ability (dedication and lifestyle) to do super long training might also be a key to drive fat oxidation. Do you have data to support that your workout duration distribution has not changed and that weight loss and macronutrients distribution (+strides) were the drivers of your improvement this year ?
- On your hard workouts days, I feel like you still stay under 250g of carbs, am I right ?
- After the 1st of February I am amazed that you are hovering over 2000 kcal only on lighter days. I know BMR and EE during exercise are hard to « measure » but still, it strucks me…
- Do you plan rest days ? I guess you keep the carbs super low when you do no train ?
- I feel like it’s difficult to get my calories needs if I don’t eat often. Do you think it’s even more ok to eat often when you eat fat and protein as snacks vs carbs ?
- I find super interesting that you keep the fat oxidation abilities when having some carbs before exercising, that’s big news to me.
- About LCHF and "LMHR" people, we have already discussed this... the Keto-CTA study has been quite something on socials (the speed of rising of the plaque is stunning !) and I am highly convinced that the keto crowd is falling into cognitive biais when they don't take actions in front of a big LDL-C or CAC score. Frankly, even just thinking of going on Periodized Nutrition and knowing my ability to produce LDL-C, I would put myself on a statin giving that I would rise drastically saturated fats in my diet. I know you have proven with adding a lot of fibers that we can manage LDL with periodized nutrition but my previous experiments show me that I don't reduce much my LDL with psyllium...
- We all crave for more recipes and menu ;) let’s add a cooking section to the blog ;)
- Eventually graze mille for sharing all your journey with us with such dedication. You add Signal in a noisy world of information.
thank you my friend. My question for you, reading this, is the following: are the things that we like, the ones that make us better? :)
Sometimes they are, or for some people they might be (e.g. eating higher amounts of carbs and training many hours, clearly works for some people), but the fact that it works for them, does it mean that it works for us too? In my case the answer is a clear no. Even the story about volume and long duration exercise overriding dietary choices, as you can imagine I'd love for that to be true, but my data shows the opposite: I train high volume, I stay out entire days, and my fat ox sucks, which is not just "about fat ox" it's about how poorly I perform in long races wrt to the short ones, despite training only for the long ones! I changed because of my interest in improving outcomes that matter (health and performance) not because of a metric, but the metric here was indicative of an issue in my metabolism. Hence something needed to change, and this change, made all the difference, as documented in my long-distance performance (and my health) this year.
If your fat ox is good already, it is unlikely that you need to go through the same, but it is too easy to find someone who speaks to our bias and then take that as the right thing to do :)
Happy to discuss more about all the points above when we chat!
First of all, thank you Marco for sharing such a detailed and transparent account.
It’s rare to see a personal case study so well-documented, with data, reflections, and practical tools.
That said, I’d like to raise a few methodological doubts — as an external reader — and I fully acknowledge that I may have misunderstood some aspects or conditions of your testing protocol.
The reported increase in fat oxidation is one of the most intriguing elements, but it’s difficult to confidently attribute it to a chronic adaptation. The test was performed only once, with no true pre/post comparison using an identical protocol, and in a metabolic state likely influenced by at least 2 days of low-carb intake and possibly slight caloric restriction.
These conditions are known to acutely elevate fat oxidation even in the absence of structural (e.g., mitochondrial) adaptations.
Moreover, the improvements in performance metrics (pace, threshold, running economy) appear largely consistent with the 10 kg weight loss, which alone could explain most of the positive physiological changes.
It’s therefore hard to isolate the specific impact of nutrition periodization, especially given concurrent changes in diet quality, training composition, and overall context.
In short, I consider your self-experiment an excellent starting point and an inspiring framework for further exploration, but I believe more robust conclusions would require controlled studies, with standardized pre/post testing and systematic comparisons against alternative strategies (e.g., consistent high-carb, caloric deficit without periodization, etc.).
Thanks again for your work and for openly sharing this journey — it’s rare to see such a thoughtful balance between data, self-awareness, and curiosity for improvement.
thanks! And of course, I agree with the points brought up, I can only document my process and the data collected.
I would stress that there is no performance improvement wrt when I was the same body composition, for distances up to the half marathon, but I do perform much better where first I was limited by my non-existent fat-oxidation (e.g. 50 km or longer), hence I think we have good indications that the change to periodized nutrition resulted in the expected outcome (very specific to a condition in which carbohydrate stores are running out, which is not the case for shorter distances). Keep in mind that when looking at running economy and metabolic flexibility I am comparing to myself when I was the same body composition as now, and running my best times, hence the comparison is not impacted by weight/body composition.
This being said, as you say, this is just my experience, not something that everyone needs to do, especially if their fat-ox is within normal ranges (mine wasn't, hence I might be benefiting more than others) or if they target shorter events.
I'll do plenty of additional testing in the future as I am setting up a lab with a metabolic cart, and I have many questions still to answer :)
Thank you again — your openness and transparency are always truly valuable.
I still have a few doubts, simply because I believe we’re dealing with a field that is inherently complex to interpret.
That said, I deeply appreciate the fact that you’re continuing to test yourself with more precise and replicable tools — it’s the best way to turn personal experience into something useful for others.
In a way, I even envy you for it.
Congratulations once again on your work and the clarity with which you’re pursuing your journey.
thanks Jeff! During hard workouts I normally have a gel mid-session, e.g. if I'm doing a 4 x 2000m, I'd have one after the first two reps, and similarly for other hard sessions. An alternative could be one after the warmup, but normally I fuel them well also with breakfast, hence I tend to eat only during. This has not changed wrt before periodized nutrition. For long, hard runs, e.g. 30-40 km with segments at marathon or 50 km pace, I do fuel a bit differently, and while before I was trying to get to eat 1 gel every 6 km, now I try to get to 1 every 8-9 km, so lowering a bit the frequency and seeing how I do (this is more experimental).
thanks Adam! The deficit was intentional and unrelated to reducing CHO intake, I just thought I needed to get back where I was 2 years prior to this (I had lost much of the weight already before shifting to lower CHO, simply eating high CHO but with a caloric deficit). Maybe it is easier to lose weight on a certain diet, but in my experience it was a similar process to when I did the same years before (also high CHO but caloric deficit, I lost the same weight in the same time I did this year) - so in my experience both macronutrient distributions led to the same outcome in terms of body composition, and the deficit was the only thing that mattered (again, just in my experience, not in general). Here I documented the weight loss because it was part of the process I went through, but I think the interesting part is the macronutrient change and what that brings in terms of fat oxidation, as only the macronutrient change and periodization of CHO led to a huge change in fat ox (while before, even when losing much weight and reducing body fat, I still had fat ox of "zero", as I was eating high carb, and apparently my body works this way - not everyone that eats lots of carbs has poor fat ox, as genetics is always another key factor). I hope this answers your question!
Sure does, thanks for the quick reply. So if I were to start this and want to maintain weight, I just adjust fats and proteins to match my calorie requirements day to day? Depending on training intensity, etc
yes, it has been a few months now that I've been stable in weight (February to today) and the way I think about it from a practical point of view is to start with protein, and then depending on training, add either more carbs (hard day or long day) or else (easy day). I shared recently 2 podcasts that you can find on my feed, where I tried to discuss a bit more also these more practical aspects, should you be interested.
Hi Marco. Very interesting article and insights...as usual with your post. Any suggestion to make an accurate indirect calorimetry test in Italy? Thanks
thanks a lot Antonello! Unfortunately my 'trusted lab' is in Amsterdam, but in theory any exercise science lab that offers testing should be fine, as long as they provide you with the breath-by-breath VO2 and VCO2 data (something important to check before booking the test). Maybe via some private personal trainer or medical center that offers these services in your area.
Fantastic N=1 study and awesome to hear about improvement in blood biomarkers. I completely agree that, especially for folks with genetic predispositions towards high cholesterol (and associated issues), following a low-carb diet without considerations of saturated fats and fiber intake can yield poor markers. And thank you for linking to Dr. Williden's podcast on the subject- I have found her to be a wealth of knowledge regarding nutrition and metabolic flexibility in general. Really trying to get the athletes I work with to buck the trend of "i'm an athlete so I can eat whatever I want" mentality. Thanks for sharing!
Hey Marco! How do you come up with the amount of calories you need each day? Are you wearing/recommending a certain device for that? True calorie needs obviously can not be measured but only estimated, so I was wondering how you assess them? Especially on rest days you might need much more than your watch etc might say, right? Greetings from Innsbruck!
hi Tobias! no device, during the caloric deficit phase I wasn't tracking anything for weeks (not intake nor expenditure), but going by feel. Similarly now I also go by feel and do not track anything. Once we stop eating just because food is around, and overeating at every meal, it's easy to get in tune with our body as it gives you the right cues (i.e. "hunger"). As you say, intake and expenditure estimates are all very inaccurate and I only used a rough estimate for the period in which I tracked manually, which mostly was to learn more about the macros (hence the input I logged in the excel file for a few weeks) and to collect some data for this report. For that purpose, I simply used estimated calories from training and estimated basal metabolic rates from formulas (for expenditure) and the macros from the food I was logging (as intake). The error can be huge, and I would discourage to attempt to track expenditure (people can get quite obsessive, tracking every step they take, which defeats the purpose of getting more in tune with their bodies... !), but again, on my end I wasn't using this for anything practical, at the end of the day you have a tool you can use to see the outcome metric (i.e. check your weight with a scale), and therefore over weeks it was easy to see if I was in deficit or stable. I wasn't trying to hit a deficit of 1000 kcals at the beginning: I simply knew that to drop the weight I had to be hungry at times, which is what I had done also in the past, and when I did the math weeks later, I saw that I was around that number (based on kg lost / week). Now I have been the same weight from February to May, which I do measure a few times per week, as some feedback is useful to keep us on track, but I have not tracked any of my expenditure or intake in months. I think there is something to manually logging intake, we learn a lot from that, but expenditure tracking is mostly inaccurate and can lead people to focus on the numbers as opposed to the body's cues / becoming more aware, which is what I think matters the most. The same argument can be made for the scale, but I think there is a difference between "getting some feedback / output at certain time intervals" and "tracking every second obsessively", it's the same difference I see between a morning HRV measurement (useful) and continuous HRV tracking (total nonsense). I hope this somewhat answers your question!
Thank you for taking your time to answer my question!
To be completely honest, this is exactly what I was hoping to hear from you. I struggle with disordered eating and want to get away from counting calories, because I know how inaccurate it is and because it really ruined my relationship with food, sports and life in the past...
Listening to the body is definitely a skill that needs to be trained. It is not easy, but I am trying my best to fight the ED and relearn to get in touch with my intuition.
It helps me a lot to know that you agree that it is neither sustainable nor necessary to be counting everything we eat. Focusing on macros and quality nutrition, together with adequately fueling our workouts and listening to our bodies are the things that really matter the most.
Thanks again for your answer!! I actually even started a list with people/athletes who I respect or look up to that don't count calories, and I am glad I can put you up on it as well :D
Marco, this was a thorough, non-dogmatic write up. I’m operating under the assumption that you’re only counting net carbohydrates in the above numbers, correct?
thank you Skyler, much appreciated. In these plots I was only counting carbohydrates (regardless of fiber), hence total carbohydrates are reported. Later I shifted to counting net carbohydrates, but this is not included in the reports above (e.g. if I had beans or farro or chia seeds, I counted the total carbohydrates for those foods and logged them). Does this answer your question?
Yes, thank you. I cycle my carbs but end up with a lot of fiber, hence my question.
My background is largely strength/power/fitness (MS Exercise & Sport Science) but I find it interesting that individuals from that side of the world have long used this approach, specifically individuals like John Bernardo PhD.
While the idea of “needing” carbs around training matters “more” for stage events, putting starchy carbs around higher effort workouts, as is often the case in the S&C world, makes so much sense. If you’re an ultra distance athlete training low intensity most of the time, shouldn’t you be protecting your carbs as a function of your relatively high fat max day to day? What do you need massive carbs for on a recovery day?
Those are rhetorical questions at the end. Thank you again!
I have some experience with periods of caloric deficit in my past, and what I found in most cases was a suppression of lactate values at submax intensity which suggests a better fuel economy (didn’t have the possibility to measure fat ox).
Normally what I see after going back to a normal diet is that the values go back to normal.
How much of your results do you think might be due to the caloric deficit compared to the lower carb approach?
What I understood from the literature on lower carb approaches is that once you go back to normal diets the fat ox tends to go back to normal values again, so you would need to protract the diet up until race day. Wouldn’t it be risky (higher immuno-suppression exc)? If doing so, you think one/two days of higher carbs before race would be enough to top up glycogen levels without compromising the fatox values reached with the dietary intervention?
Yes, diet is key. The change in fat ox is entirely due to the diet in this case (I know this because I went through the exact same in the past, losing the same weight, performing similarly, but eating high-carb - just with a high deficit - and my fat ox was near 0). Metablism shifts because of the macro distribution, not because of the weight loss or caloric deficit.
I agree that I need to keep up the diet, otherwise I would revert back to poor fat ox. That's okay, as I think the periodized approach is better also for health (it's the chronic high carb and sugar intake that causes higher inflammation, etc.).
Regardiing timing of the dietary change, unfortunately typically it takes 6-8 weeks to shift metabolism, hence a few days would not do the job and I do need to keep this up until race day. Just to reiterate, I do eat carbs, I just periodize the intake, so typically I have 2 days or 2 days and a half in a week that are higher carb and about 5 days low carb. The exact amounts will depend on the type of training (intensity and duration).
I'm sure others (like yourself) have a much better fat ox than me even on a high carb diet, but for me unfortunately that is not the case, hence I need to periodize a bit more strictly :)
Thank you again and all the best for your training!
this is spectacular explanation of N=1 experiments with lots of insights
so excellent data match with personal needs and intuitions, paying attention to how quality of life during day, sleep, performance, recovery look like in these month, adjusting for different training and... yess I think a bit of effort and courage to test something extremely new
chapeau @marco :))))))))
Grazie Ilaria! Really appreciate the kind words from you 🙏
I trust in N= 1 experiments with integration of data, intuitions and feelings!!! A must read
Awesome case study! Thanks Marco
Thank you!
I remember you telling me about the experiment you started back in February in Gran Canaria when we meet. I am super excited to see how diligent you were with this and the documentation, as well as the ability to share openly so many details about it. Thank you Marco and most likely I will reach out to you for few ideas I have with Kasia, but I need her to buy in. Hope to meet you soon! 🤙🚀 Abrazo fuerte y besos para Alessandra ⛰️🏃♂️🔥
I remember you telling me about the experiment you started back in February in Gran Canaria when we meet. I am super excited to see how diligent you were with this and the documentation, as well as the ability to share openly so many details about it. Thank you Marco and most likely I will reach out to you for few ideas I have with Kasia, but I need her to buy in. Hope to meet you soon! 🤙🚀 Abrazo fuerte y besos para Alessandra ⛰️🏃♂️🔥
anytime my friend! Great memories from those days
Absolute goldmine. Thank you
thank you Marian!
I have done my own experimenting with precisely this type of nutrition some years ago (2017-2018). I didn't call it periodisation but "strategic use" of carbs :D. However, I had no access to the advanced measurement devices nor the scientific knowledge you obviously posses. What I was able to measure though, was the increase in fat oxidation while running the same pace after about 4 months of using similar nutrition protocol you describe. This was done in a professional sports lab, so really could see a change. The result was that I was able to sustain a given pace for much longer while consuming roughly the same amount of carbs per hour (about 45g). I ran ultras at the time (UTMB and such) so my goal was to get around the loop as fast as possible while being able to sustain fuelling for around 28-29 hours of racing. I had not much knowledge about HRV at the time so I did not measure it but your insights and the details you go into are fascinating and truly a goldmine for people like me. Thanks again!
great to hear Marian, this is very similar to my experience, thank you so much for taking the time!
Great article, as always. One reflection I had on your gastrointestinal issues: did/have you considered fermented foods as additions to meals and snacks and/or probiotics?
thank you. Definitely something to look into, I appreciate the input. For lower carb days, issues are basically resolved - something eventually I could pin down at least partially to gluten, as I do not have the same issues also when I reintroduce certain types of carbs that do not contain it - but on higher carb days or especially when I have a couple of days in which I have more and maybe I also have more ‘standard lower quality carbs’ (even just bread and pasta), it seems that I can have more problems. Work in progress.
Thank you so much for your work and sharing amazing insights and details. I am by myself aging recreational female athlete and I plan my second MDS next year. I have problems with carbs during training and was "dancing" with different ideas about nutrition. That said while modifying my diet so far I have los 6 kg (~4%fat). Now I am in the process of moving toward complex carbs, eliminating simple from diet. And as a next step I consider further periodization. BUT:) My main fear is about ramping up protein intake. As I have calculated from your data, you have about 2,5 grams per day. Is that OK from longterm health issues and did you check UREA levels in blood? I am very easy on protein and can take like 2,2 grams per kg per day, but try to limit to 2 gr. May be this is not as serious as I think. I have no answer for this so far.
thanks Nadya! I think recommendations for athletes are around 2g/kg, hence that's what we are currently advised to do. My numbers might have some errors (there are just estimates), and there can be days in which the intake is a bit higher, as there are days in which the intake is certainly lower (if I'm having more higher quality carbs or training less, there will be less protein). In my view an important aspect remains always the quality of the diet, the variety of protein sources, etc. - I think that if we make an effort to eat well, whole foods, etc. - it is unlikely that we are creating issues, I think (while there might be studies showing a very high protein intake is not recommended, these are unlikely to be in athletes and probably involve a diet in which protein might come almost exclusively from meat or red meat, as it seems to be common in certain groups). All the best for your training!
Ciao Marco,
Perdonatemi per questo lungo commento, ma leggere e rileggere il vostro blog e ascoltare i podcast stimola davvero la mia piccola mente appassionata di sport!
- Again, congratulations for your dedication, navigating such diet changes in the pursuit of racing goals is purely amazing
- Was there a gradual cut of carbs before December/January or was it more direct process ?
- It would be nice to have the written percentages on the histograms of your macro distribution
- I would also be interested in knowing your energy expenditure at the pace you take for examples in your oxidation rates
- I see that you’re often very low in carbs (<50g) despite training everyday, that’s quite a challenge to go lower 50g of carbs. I guess you must cut off anything starchy and get your carbs from vegetables to stay this low. I will have to start a new love with broccoli if I go this way…
- I see AC back in 2008 having good results with an athlete with still quite a lot of carbs, of course everyone is different, but his strikes me : « I put this athlete on a diet of 400g of CHO/200g of (lean) Protein and 100g of (good) Fat. This represents 3300kcal/day and 48%/24%/28% macronutrient breakdown. Irrespective of whether the diet is eucaloric or not, I have found these percentages to be ideal in the base phase of training. » I have computed my macros this week and I was 39%/21%/39% and I feel like I have plenty of room in terms of fat oxidation (last time I measured I was 0.6 g/min at FatMax…)
- Also DP seems to have some divergent opinion from BS when writing « Remember that exercise duration is the most potent stimulant for fat oxidation; this is above specific macro-nutrient manipulation. » So my remark is that your ability (dedication and lifestyle) to do super long training might also be a key to drive fat oxidation. Do you have data to support that your workout duration distribution has not changed and that weight loss and macronutrients distribution (+strides) were the drivers of your improvement this year ?
- On your hard workouts days, I feel like you still stay under 250g of carbs, am I right ?
- After the 1st of February I am amazed that you are hovering over 2000 kcal only on lighter days. I know BMR and EE during exercise are hard to « measure » but still, it strucks me…
- Do you plan rest days ? I guess you keep the carbs super low when you do no train ?
- I feel like it’s difficult to get my calories needs if I don’t eat often. Do you think it’s even more ok to eat often when you eat fat and protein as snacks vs carbs ?
- I find super interesting that you keep the fat oxidation abilities when having some carbs before exercising, that’s big news to me.
- About LCHF and "LMHR" people, we have already discussed this... the Keto-CTA study has been quite something on socials (the speed of rising of the plaque is stunning !) and I am highly convinced that the keto crowd is falling into cognitive biais when they don't take actions in front of a big LDL-C or CAC score. Frankly, even just thinking of going on Periodized Nutrition and knowing my ability to produce LDL-C, I would put myself on a statin giving that I would rise drastically saturated fats in my diet. I know you have proven with adding a lot of fibers that we can manage LDL with periodized nutrition but my previous experiments show me that I don't reduce much my LDL with psyllium...
- We all crave for more recipes and menu ;) let’s add a cooking section to the blog ;)
- Eventually graze mille for sharing all your journey with us with such dedication. You add Signal in a noisy world of information.
thank you my friend. My question for you, reading this, is the following: are the things that we like, the ones that make us better? :)
Sometimes they are, or for some people they might be (e.g. eating higher amounts of carbs and training many hours, clearly works for some people), but the fact that it works for them, does it mean that it works for us too? In my case the answer is a clear no. Even the story about volume and long duration exercise overriding dietary choices, as you can imagine I'd love for that to be true, but my data shows the opposite: I train high volume, I stay out entire days, and my fat ox sucks, which is not just "about fat ox" it's about how poorly I perform in long races wrt to the short ones, despite training only for the long ones! I changed because of my interest in improving outcomes that matter (health and performance) not because of a metric, but the metric here was indicative of an issue in my metabolism. Hence something needed to change, and this change, made all the difference, as documented in my long-distance performance (and my health) this year.
If your fat ox is good already, it is unlikely that you need to go through the same, but it is too easy to find someone who speaks to our bias and then take that as the right thing to do :)
Happy to discuss more about all the points above when we chat!
So much to explore then…
First of all, thank you Marco for sharing such a detailed and transparent account.
It’s rare to see a personal case study so well-documented, with data, reflections, and practical tools.
That said, I’d like to raise a few methodological doubts — as an external reader — and I fully acknowledge that I may have misunderstood some aspects or conditions of your testing protocol.
The reported increase in fat oxidation is one of the most intriguing elements, but it’s difficult to confidently attribute it to a chronic adaptation. The test was performed only once, with no true pre/post comparison using an identical protocol, and in a metabolic state likely influenced by at least 2 days of low-carb intake and possibly slight caloric restriction.
These conditions are known to acutely elevate fat oxidation even in the absence of structural (e.g., mitochondrial) adaptations.
Moreover, the improvements in performance metrics (pace, threshold, running economy) appear largely consistent with the 10 kg weight loss, which alone could explain most of the positive physiological changes.
It’s therefore hard to isolate the specific impact of nutrition periodization, especially given concurrent changes in diet quality, training composition, and overall context.
In short, I consider your self-experiment an excellent starting point and an inspiring framework for further exploration, but I believe more robust conclusions would require controlled studies, with standardized pre/post testing and systematic comparisons against alternative strategies (e.g., consistent high-carb, caloric deficit without periodization, etc.).
Thanks again for your work and for openly sharing this journey — it’s rare to see such a thoughtful balance between data, self-awareness, and curiosity for improvement.
thanks! And of course, I agree with the points brought up, I can only document my process and the data collected.
I would stress that there is no performance improvement wrt when I was the same body composition, for distances up to the half marathon, but I do perform much better where first I was limited by my non-existent fat-oxidation (e.g. 50 km or longer), hence I think we have good indications that the change to periodized nutrition resulted in the expected outcome (very specific to a condition in which carbohydrate stores are running out, which is not the case for shorter distances). Keep in mind that when looking at running economy and metabolic flexibility I am comparing to myself when I was the same body composition as now, and running my best times, hence the comparison is not impacted by weight/body composition.
This being said, as you say, this is just my experience, not something that everyone needs to do, especially if their fat-ox is within normal ranges (mine wasn't, hence I might be benefiting more than others) or if they target shorter events.
I'll do plenty of additional testing in the future as I am setting up a lab with a metabolic cart, and I have many questions still to answer :)
Thanks again for reading and for your thoughts!
Thank you again — your openness and transparency are always truly valuable.
I still have a few doubts, simply because I believe we’re dealing with a field that is inherently complex to interpret.
That said, I deeply appreciate the fact that you’re continuing to test yourself with more precise and replicable tools — it’s the best way to turn personal experience into something useful for others.
In a way, I even envy you for it.
Congratulations once again on your work and the clarity with which you’re pursuing your journey.
All the best,
Lorenzo
Hey Marco, great article, thank you. Can you talk about how you fuel during workouts that have intensity?
thanks Jeff! During hard workouts I normally have a gel mid-session, e.g. if I'm doing a 4 x 2000m, I'd have one after the first two reps, and similarly for other hard sessions. An alternative could be one after the warmup, but normally I fuel them well also with breakfast, hence I tend to eat only during. This has not changed wrt before periodized nutrition. For long, hard runs, e.g. 30-40 km with segments at marathon or 50 km pace, I do fuel a bit differently, and while before I was trying to get to eat 1 gel every 6 km, now I try to get to 1 every 8-9 km, so lowering a bit the frequency and seeing how I do (this is more experimental).
Was the calorie deficit intentional to lose weight? Or was it a consequence of reducing CHO intake?
This is fascinating and I will be trying this out on myself, as I have access to a full metabolic cart at work.
thanks Adam! The deficit was intentional and unrelated to reducing CHO intake, I just thought I needed to get back where I was 2 years prior to this (I had lost much of the weight already before shifting to lower CHO, simply eating high CHO but with a caloric deficit). Maybe it is easier to lose weight on a certain diet, but in my experience it was a similar process to when I did the same years before (also high CHO but caloric deficit, I lost the same weight in the same time I did this year) - so in my experience both macronutrient distributions led to the same outcome in terms of body composition, and the deficit was the only thing that mattered (again, just in my experience, not in general). Here I documented the weight loss because it was part of the process I went through, but I think the interesting part is the macronutrient change and what that brings in terms of fat oxidation, as only the macronutrient change and periodization of CHO led to a huge change in fat ox (while before, even when losing much weight and reducing body fat, I still had fat ox of "zero", as I was eating high carb, and apparently my body works this way - not everyone that eats lots of carbs has poor fat ox, as genetics is always another key factor). I hope this answers your question!
Thanks again Marco! Much appreciated
Sure does, thanks for the quick reply. So if I were to start this and want to maintain weight, I just adjust fats and proteins to match my calorie requirements day to day? Depending on training intensity, etc
yes, it has been a few months now that I've been stable in weight (February to today) and the way I think about it from a practical point of view is to start with protein, and then depending on training, add either more carbs (hard day or long day) or else (easy day). I shared recently 2 podcasts that you can find on my feed, where I tried to discuss a bit more also these more practical aspects, should you be interested.
Hi Marco. Very interesting article and insights...as usual with your post. Any suggestion to make an accurate indirect calorimetry test in Italy? Thanks
thanks a lot Antonello! Unfortunately my 'trusted lab' is in Amsterdam, but in theory any exercise science lab that offers testing should be fine, as long as they provide you with the breath-by-breath VO2 and VCO2 data (something important to check before booking the test). Maybe via some private personal trainer or medical center that offers these services in your area.
Fantastic N=1 study and awesome to hear about improvement in blood biomarkers. I completely agree that, especially for folks with genetic predispositions towards high cholesterol (and associated issues), following a low-carb diet without considerations of saturated fats and fiber intake can yield poor markers. And thank you for linking to Dr. Williden's podcast on the subject- I have found her to be a wealth of knowledge regarding nutrition and metabolic flexibility in general. Really trying to get the athletes I work with to buck the trend of "i'm an athlete so I can eat whatever I want" mentality. Thanks for sharing!
thank you Mikki!
Hey Marco! How do you come up with the amount of calories you need each day? Are you wearing/recommending a certain device for that? True calorie needs obviously can not be measured but only estimated, so I was wondering how you assess them? Especially on rest days you might need much more than your watch etc might say, right? Greetings from Innsbruck!
hi Tobias! no device, during the caloric deficit phase I wasn't tracking anything for weeks (not intake nor expenditure), but going by feel. Similarly now I also go by feel and do not track anything. Once we stop eating just because food is around, and overeating at every meal, it's easy to get in tune with our body as it gives you the right cues (i.e. "hunger"). As you say, intake and expenditure estimates are all very inaccurate and I only used a rough estimate for the period in which I tracked manually, which mostly was to learn more about the macros (hence the input I logged in the excel file for a few weeks) and to collect some data for this report. For that purpose, I simply used estimated calories from training and estimated basal metabolic rates from formulas (for expenditure) and the macros from the food I was logging (as intake). The error can be huge, and I would discourage to attempt to track expenditure (people can get quite obsessive, tracking every step they take, which defeats the purpose of getting more in tune with their bodies... !), but again, on my end I wasn't using this for anything practical, at the end of the day you have a tool you can use to see the outcome metric (i.e. check your weight with a scale), and therefore over weeks it was easy to see if I was in deficit or stable. I wasn't trying to hit a deficit of 1000 kcals at the beginning: I simply knew that to drop the weight I had to be hungry at times, which is what I had done also in the past, and when I did the math weeks later, I saw that I was around that number (based on kg lost / week). Now I have been the same weight from February to May, which I do measure a few times per week, as some feedback is useful to keep us on track, but I have not tracked any of my expenditure or intake in months. I think there is something to manually logging intake, we learn a lot from that, but expenditure tracking is mostly inaccurate and can lead people to focus on the numbers as opposed to the body's cues / becoming more aware, which is what I think matters the most. The same argument can be made for the scale, but I think there is a difference between "getting some feedback / output at certain time intervals" and "tracking every second obsessively", it's the same difference I see between a morning HRV measurement (useful) and continuous HRV tracking (total nonsense). I hope this somewhat answers your question!
Thank you for taking your time to answer my question!
To be completely honest, this is exactly what I was hoping to hear from you. I struggle with disordered eating and want to get away from counting calories, because I know how inaccurate it is and because it really ruined my relationship with food, sports and life in the past...
Listening to the body is definitely a skill that needs to be trained. It is not easy, but I am trying my best to fight the ED and relearn to get in touch with my intuition.
It helps me a lot to know that you agree that it is neither sustainable nor necessary to be counting everything we eat. Focusing on macros and quality nutrition, together with adequately fueling our workouts and listening to our bodies are the things that really matter the most.
Thanks again for your answer!! I actually even started a list with people/athletes who I respect or look up to that don't count calories, and I am glad I can put you up on it as well :D
thank you Tobias! Wishing you all the best
Marco, this was a thorough, non-dogmatic write up. I’m operating under the assumption that you’re only counting net carbohydrates in the above numbers, correct?
thank you Skyler, much appreciated. In these plots I was only counting carbohydrates (regardless of fiber), hence total carbohydrates are reported. Later I shifted to counting net carbohydrates, but this is not included in the reports above (e.g. if I had beans or farro or chia seeds, I counted the total carbohydrates for those foods and logged them). Does this answer your question?
Yes, thank you. I cycle my carbs but end up with a lot of fiber, hence my question.
My background is largely strength/power/fitness (MS Exercise & Sport Science) but I find it interesting that individuals from that side of the world have long used this approach, specifically individuals like John Bernardo PhD.
While the idea of “needing” carbs around training matters “more” for stage events, putting starchy carbs around higher effort workouts, as is often the case in the S&C world, makes so much sense. If you’re an ultra distance athlete training low intensity most of the time, shouldn’t you be protecting your carbs as a function of your relatively high fat max day to day? What do you need massive carbs for on a recovery day?
Those are rhetorical questions at the end. Thank you again!
Hello Marco, really interesting article.
I have some experience with periods of caloric deficit in my past, and what I found in most cases was a suppression of lactate values at submax intensity which suggests a better fuel economy (didn’t have the possibility to measure fat ox).
Normally what I see after going back to a normal diet is that the values go back to normal.
How much of your results do you think might be due to the caloric deficit compared to the lower carb approach?
What I understood from the literature on lower carb approaches is that once you go back to normal diets the fat ox tends to go back to normal values again, so you would need to protract the diet up until race day. Wouldn’t it be risky (higher immuno-suppression exc)? If doing so, you think one/two days of higher carbs before race would be enough to top up glycogen levels without compromising the fatox values reached with the dietary intervention?
Thanks!
ciao Mattia!
Yes, diet is key. The change in fat ox is entirely due to the diet in this case (I know this because I went through the exact same in the past, losing the same weight, performing similarly, but eating high-carb - just with a high deficit - and my fat ox was near 0). Metablism shifts because of the macro distribution, not because of the weight loss or caloric deficit.
I agree that I need to keep up the diet, otherwise I would revert back to poor fat ox. That's okay, as I think the periodized approach is better also for health (it's the chronic high carb and sugar intake that causes higher inflammation, etc.).
Regardiing timing of the dietary change, unfortunately typically it takes 6-8 weeks to shift metabolism, hence a few days would not do the job and I do need to keep this up until race day. Just to reiterate, I do eat carbs, I just periodize the intake, so typically I have 2 days or 2 days and a half in a week that are higher carb and about 5 days low carb. The exact amounts will depend on the type of training (intensity and duration).
I'm sure others (like yourself) have a much better fat ox than me even on a high carb diet, but for me unfortunately that is not the case, hence I need to periodize a bit more strictly :)
Thank you again and all the best for your training!