[Aurornis]

If you’ve been regularly eating meals multiple times per day, it will take your body much longer to start functioning well during a fast.

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.

[wslh]

Just yesterday I mentioned here that I train for (olympic) triathlons [1], and in the context of that and this thread I need to eat much more because I lose significant weight AND, I feel much more nervous if I fast, and I am not a nervous person.

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.

[1] https://news.ycombinator.com/item?id=40533944

[mistrial9]

great going and good on you for your health BUT endurance athletics represents only an important but tiny fraction of the lives of adults. General conversation around health, fitness and tuning is easily derailed by outliers and insufficient context!! office workers with weak backs and wrists end up arguing with 20+ hour a week gym people over some aspect of diet, and then they talk past each other.. no problems with the comment but perspective and context are everything when talking health.

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.

[wslh]

I was clear in my comment and in a reference to a previous comment that people are different. I never recommended that you should follow my way of life but I shared some aspects of my healthy life because I considered that I am not doing any exceptional thing, healthy human-wisely.

> 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.

[techcode]

As mentioned video I saw was newer than the news article. In the video I think doctor was talking about events like https://www.lowcarbusa.org/pioneering-ketogenic-management-f...

[techcode]

In another comment I mentioned UK doctors (so folks closer to couch potato than ultra long distance runners) basically saying let's do this.

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...

[_yb2s]

There is a ton of research on this… high intensity exercise requires glycogen and cannot be done at the same level without a high carbohydrate intake. It is possible to walk almost indefinitely in ketosis, but it won’t really work for any kind of athletic competition.

[techcode]

Years ago I saw some YouTube videos featuring sports folks - from marathon runners, to someone row/paddling across the ocean - all of them being long term (basically permanent) on keto.

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.

[_yb2s]

It's pretty fascinating stuff, and totally doable. I stand corrected on the "any athletic event"- what I said doesn't apply to ultra long duration lower intensity events. Endurance will be higher but peak power outputs lower. For endurance focused events like the ones you described, I could see it being an advantage- everyone will run out of glycogen, but those already keto-adapted won't need to suddenly start trying to adapt during the event.

[Attummm]

Contrary to popular belief, fasting actually increases metabolism.

https://www.nature.com/articles/s41598-018-36674-9

[layla5alive]

Temporarily, and then it is dramatically reduced.

Jesus people, please stop with the unequivocal statements about equivocal/nuanced/complex things.

[shlant]

> Temporarily, and then it is dramatically reduced

No change of diet will "dramatically reduce" metabolism. This is entirely unsubstantiated

[_yb2s]

Not true, unlike many other mammals humans can survive a long time without food largely because the liver regulates metabolism in response to calorie intake. The thyroid hormone T3 is the main regulator aka “gas pedal” of cellular metabolism, and conversion of inactive T4 into T3 is done mostly by the liver. Conversion is halted when fasting or severely restricting calories… much to the frustration of dieters. This is why mainstream advice is to not lose weight too fast.

[layla5alive]

Indeed, and there are a few other mammals for which there are mechanisms to reduce ATP generation, reduce VO2, etc., and some which do it much better than humans do. Emperor Penguins, for example.

[Attummm]

Did you read the study? The study is about prolonged fasting, up to 58 hours.

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.

[_yb2s]

You are misunderstanding what that means… it is an up regulation of catabolism- breaking down other molecules and tissues for survival during fasting. Overall metabolic rate is drastically reduced during prolonged fasting, which is good, it preserves nutrients for survival.

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.

[Attummm]

Catabolism is an integral component of metabolism. Both anabolic (growth) and catabolic (breakdown) processes constitute the entirety of metabolic activities.

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.

[_yb2s]

Yes, every chemical reaction in a living system is part of metabolism, but in common speech when we talk about increasing metabolism we are specifically talking about increasing the metabolic rate- e.g. calories burned to generate ATP per an amount of biomass. What is happening in that paper is the opposite of a "metabolic increase" in that context. You are trying to correct people by citing a paper that supports what they were saying, and not what you are saying.

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.