Is this the Nail in the Fat Adaption Coffin - NOT

Gravel Worlds 2022

It is always interesting when a new paper comes out - especially when it reveals confirmation bias whichmost of the time is the case.  By the way we all have them - confirmation biases that is - the thing is to recognize them so you can check them at the door when making conclusions from papers and studies.

Such is the case with a recent study (https://www.mdpi.com/2072-6643/16/2/318) entitled: A Five-Week Periodized Carbohydrate Diet Does Not Improve Maximal Lactate Steady-State Exercise Capacity and Substrate Oxidation in Well-Trained Cyclists compared to a High-Carbohydrate Diet

Of course the tile spurred many of those who are largely carb-centric to claim this was the nail in the preverbal coffin of those who put forward a different paradigm.  Sort of interesting that this one paper leads to so many articles such that the public starts to think there is some ground breaking findings but it is simply a number of authors espousing their biases were indeed correct based on a single study.  A study by the way that I think these purveyors of the death of fat adaptation - Using Fat as Fuel -  incorrectly interpret. Here are some examples:

GCN - admittedly they do little the is actually scientific but is more entertainment based:  
Velo - Nothing new for them as if anyone writes anything that may be used to dispel fat adaption they are all over it:   
Trail Runner Magazine - The author admits at least that this study made him feel good- glad he fell affirmed - about his bias: 

So what is in this study - well for one I will give my take but please read it for yourselves.  I find too often people tend to not look into the studies themselves and thus take for gospel whatever they are told.  

This is a quick take from the abstract/study and my observations:
“There is a growing interest in studies involving carbohydrate (CHO) manipulation and subsequent adaptations to endurance training. This study aimed to analyze whether a periodized carbohydrate feeding strategy based on a daily training session has any advantages compared to a high-carbohydrate diet in well-trained cyclists.”

So right off the bat you see this is not about fat adaption or even low carb but about how manipulating carbs might, or might not “increase” performance.  I can tell you very few of us that think Fat Adaption is a great tool for health and performance say that one will go faster, jump higher, etc on a low carb diet.  Most simply say you do not need a high carb diet to do so.  Then there are some, like we at Vespa/OFM, that do say that to better ones “performance” one needs to use carbs strategically as required for a given effort - thus using the fuel required for a given effort and that with training you can up the effort that canoe covers by fat but there is a limit - just higher than most will say.  Also, keep in mind most that endorse a fat adapted diet also are not simply looking at how one performs today but also about health in general for the future.

Next there is the set up for the study - First the Who:
“Seventeen male cyclists classified as highly trained [22] volunteered to participate in this study. All participants were training 15 to 20 h per week and competing in the U23 national-level cycling categories before the study. Participants undertook the study in early November after a two-week post-season break and were informed about the tests to be performed. All participants signed an informed consent form before participating in the study, which was approved by the local Research Ethics Committee (CEISH 113/2019).”

Now while I find it interesting to know what the more elite athletes do and how they train the vast majority that will read most articles that reference this study and their conclusions do not fit most of those in the study.  So, in this case these are highly trained - not the average rider/athlete.  Then you find they are under 23 so they are fit young guys - who in general have not jacked up their metabolism yet and can get by with any number of errors nutritionally.  Also, they in general do not worry about the future as most of us do, or should, and if you are older have less time to correct errors.  Thus, while many use this article to make some general conclusions just seeing who this study was about does not align with a very, very large part of the population.

The Study Protocol:
“Seventeen trained cyclists (VO2peak = 70.8 ± 6.5 mL·kg−1·min−1) were divided into two groups, a periodized (PCHO) group and a high-carbohydrate (HCHO) group. Both groups performed the same training sessions for five weeks. In the PCHO group, 13 training sessions were performed with low carbohydrate availability. In the HCHO group, all sessions were completed following previous carbohydrate intake to ensure high pre-exercise glycogen levels. In both groups, there was an increase in the maximal lactate steady state (MLSS) (PCHO: 244.1 ± 29.9 W to 253.2 ± 28.4 W; p = 0.008; HCHO: 235.8 ± 21.4 W to 246.9 ± 16.7 W; p = 0.012) but not in the time to exhaustion at MLSS intensity.”

OK, a lot here but what I can tell you carb-periodization is not fat adaption and the fact this was done over only 5 weeks and done as it was will not allow the lower/periodized carb group to get their bodies to use fat as it was designed to do and the most efficiently.  This is where I see a major flaw - not in the study per se as it is what they were looking at - in how many read this study.  The study was to see if the manipulation of carbs would lead to “BETTER” performance not to see if being fat adapted or lower carb or using carbs strategically would work but if a particular way of using carbs would improve performance.

So what were the general conclusion in the paper:
“Both groups increased the percentage of muscle mass (PCHO: p = 0.021; HCHO: p = 0.042) and decreased the percent body fat (PCHO: p = 0.021; HCHO: p = 0.012). We found no differences in carbohydrate or lipid oxidation, heart rate, and post-exercise lactate concentration. Periodizing the CHO intake in well-trained cyclists during a 5-week intervention did not elicit superior results to an energy intake-matched high-carbohydrate diet in any of the measured outcomes.”

The bottom line “Periodization” of carbs did not increase performance but also, as the study said, it did not hinder performance.  This is key and overlooked, by accident or on purpose, by many I saw that commented on this.  If there was no difference then why do high carb as you don’t need to based on this study at least.

Here are some of my take aways from this study and then I will follow up with some general observations:

1. If there was no difference then to look at it the another way the carbs did not add anything
2. The fact High Carb people went down in carbs some amount and still performed says the fat did some work.  Imagine if they really worked at fat adaption
3. These are young fit guys so a change to lower carb - even just periodized - will limit the future issues due to high sugar intake with no detriment in performance
4. The study really says little about fat adaption and only deals with high carb athlete cutting back on carbs in a particular way
5. This study does not deal with the long term effects of high carb and that you can still perform on relatively less carbs with no performance hits but long term benefits

Let me here say that those that wanted to use this to say it is time to “Take the High Carb Way or the Highway” and use this study as a proof of that did not get the study.  But I also want to say that most of those that want to dismiss fat adaption simply, and incorrectly, often look at Keto as the only way to do fat adaption.  However, we at Vespa/OFM, and there are others but not many, see the need for carbs for performance but just not the quantity that is being pushed today.  I often see articles that have to give a nod to fat burning for “less strenuous” activities since it is basic science that fat is the best fuel to burn for lower intensities.  I have even seen some articles that say that Zone 2 can be done on fat and even that many do most activity at Zone 2 but then ignore this and go to how they need to up the carbs used.  Think about this for a moment - putting the elite athlete, who is often younger, aside for a moment - even in most marathons and ultras you will be running or riding at Zone 2 for most of it and thus fat would be your best fuel.  By fat here I am not saying taking in fat exogenously but using your endogenous fat that you have copious quantities of even if you are thin and with a lower body fat percentage.  Thus you can burn fat and conserver cabs till you really need them.  Again, this does not mean you will not need carbs but will need far less and thus getting less GI distress and minimizing to netting bonking.

Check out the OFM blogs for more info and remember to read the studies that you are presented for and try and see they really say.  

  Click on images for more information and if you want more info on OFM check out this post: 

• What is OFM (Optimized Fat Metabolism)