That said, I think the mental performance benefits of fasting have been excessively hyped. I wouldn’t expect a chess player who has been fasting for multiple days to have better mental clarity. The body goes into energy preservation mode when food becomes scarce for days. That includes reduced energy expenditure for the brain.
If I am not training I have the capacity to easily fast, not issue at all with fasting, not because I follow any intermittent fasting diet, just it is the way it is. Only sample=1 but I never observed any special enhanced cognition doing that while I observe an enhanced cognition function with very basic things like sleeping well.
One more thing, I also find an improvement in cognition more with running than with swimming or biking. There are many studies about that but I give my personal experience not trying to give any conclusion for everyone. YMMV.
Most people in good health can practice some version of fasting with some common sense. Zero people with good health can train for "olympic triathalons" starting next week.. so a peek (peak?) at the life of a triathlete is interesting and perhaps commendable, but really needs calling out as an outlier in a general discussion.
> Zero people with good health can train for "olympic triathalons" starting next week..
Completely wrong. There are many paths to train for an olympic triathlon that doesn't start running, biking, and swimming and having the correct mindset, endurance, and physical state. It is like saying that a normal kid cannot learn certain things at elementary school. I am not a professional but an amateur.
Photo resembles guy I saw talking in a video about it (video was newer though) - otherwise it's first Google hit for "UK doctors diabetes keto running" and I'm yet to read through the article https://www.diabetes.co.uk/blog/2018/08/gp-type-1-diabetes-r...
And also recently some UK doctors (some of them with diabetes - I mix the types so not sure which one) decided to prove a point by going low carb/keto, while doing long runs daily (about half marathon a day), to be sure they've definitely used up all the potentially stored glycogen.
Jesus people, please stop with the unequivocal statements about equivocal/nuanced/complex things.
They observed that metabolism Increased during fasting.
> During human fasting, metabolic markers, including butyrates, carnitines, and branched-chain amino acids, are upregulated for energy substitution through gluconeogenesis and use of stored lipids.
58 hours is not a long fast in terms of total adaptability to fasting- humans can fast much longer, sometimes for months, and the biggest down regulation of metabolism usually happens later than this.
The study that I linked examines a fasting period of 58 hours. Fasting for 58 hours is considered a form of prolonged fasting. Prolonged fasting refers to an extended period without consuming food, typically lasting more than 24 hours.
I am an academic PI whose lab studies metabolism... however I use common speech when talking online so people know what I mean, I would only use more specific terminology when talking with other metabolism researchers. In many cases the common terms and academic jargon are strictly at odds, but even a researcher wouldn't say "increases metabolism" when talking about fasting adaptations, they would talk about increased metabolic flux through specific pathways and/or changes in metabolite concentrations.
The 58 hours is another example of the same- it isn't long enough to observe many of the adaptations to fasting, especially the pronounced fall in T3 and resulting decrease in metabolic rate. The fact that 58 hours would be called "prolonged" in a journal article is not relevant to the point I was making.
Let's go over some excerpts that will answer your questions.
* Metabolism increases during fasting.
> Thus diverse, pronounced metabolite increases result from greatly activated catabolism and anabolism stimulated by fasting.
* The hormone t3 produced by the thyroid is used to control metabolism. In this study they instead looked at markers for actual metabolism.
> We performed non-targeted, accurate semiquantitative metabolomic analysis of human whole blood, plasma, and red blood cells during 34–58 hr fasting of four volunteers. During this period, 44 of ~130 metabolites increased 1.5~60-fold. Consistently fourteen were previously reported. However, we identified another 30 elevated metabolites, implicating hitherto unrecognized metabolic mechanisms induced by fasting.
* The study also mentioned prolonged fasting. Which is earlier stated longer then 24 hours.
> Quantification of blood metabolites from 4 volunteers during prolonged fasting. (a) Experimental procedures employed to study metabolomic changes during human fasting for 58 hr.
> In biochemistry, a metabolite is an intermediate or end product of metabolism.
* Metabolomics[1]
> Metabolomics is the scientific study of chemical processes involving metabolites, the small molecule substrates, intermediates, and products of cell metabolism.
[0]https://en.m.wikipedia.org/wiki/Metabolite [1]https://en.m.wikipedia.org/wiki/Metabolomics
Researchers sometimes try to mitigate this limitation by measuring lactate levels in the blood, which can provide some insight into anaerobic metabolism, particularly in muscles. However, blood lactate levels primarily reflect anaerobic glycolysis and do not fully account for other anaerobic processes involving fatty acids and creatine phosphate. There are formulas to estimate these processes, but they are still approximations.
Metabolomics, on the other hand, looks directly into the cells and is not limited to only aerobic processes or anaerobic lactate production. Instead, it can identify and quantify a wide range of metabolites, which are the intermediates and end products of metabolic reactions. Thus, metabolic rate measurements provide an estimate of energy expenditure but do not directly assess the complex metabolic processes occurring within cells, whereas metabolomics offers a more direct and detailed view of cellular metabolism.
As such, the study published in Nature is within the field of metabolism and uses the latest technology to study metabolism directly. Therefor it constitutes our latest understanding of metabolism during fasting.
No change of diet will "dramatically reduce" metabolism. This is entirely unsubstantiated