Metabolic Pathways

Huh - WTH are you talking about?

The classic 2 x 20 has only 5 minutes in between. Anything more than that is just cooling down for no real reason, requiring you to work harder to get going again during the 2nd effort.

Even during VO2max training lots of rest is unnecessary, if not counterproductive.

Probably should target more like 90-130g/hr or higher, if you can muster it. Cooler temps required for higher than that.

Yes, you can, and more importantly, should. Limiting fat and fiber ensures max carb absorption and hydration is possible. Limiting protein helps too. This is very strongly evident in the scientific literature.

As a fun anecdote, my wife recently rode 310 miles and 20k elevation in 25 hrs, and consumed roughly ~1700g carbs, no fat, no fiber, and no protein, throughout. She’d have consumed closer to 2000-2400g carbs but we assumed she’d be done in 20 hrs. Mechanical issues ensued.


Also yup! Especially second sentence.


Doesn’t the amount of Carb required depend not only on how fat adapted the person is but also on his absolute power numbers. Bigger watts=More carbs

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No. Can Fat Adaptation Make You Faster?

TLDR: Don’t get “fat-adapted” via your diet. Do it via training more. Fat adaptation caused by limiting carb intake is a surefire way to reduce performance.
Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers - PMC (many others like this)

Even chronically low-carb folks can handle 90g/hr, in the vast majority of cases and I suspect up to maybe 100g/hr. Just need to nail sugar ratios to close 1:1 gluc:fruc.

Even averaging 150W merits maximizing carb intake for optimal performance (lowest RPE and HR for a given power). Thus, the vast majority of riders reading here will benefit from maximum carb intake rates.

The benefits from maximizing carb intake will probably be greater for those who sustain larger power outputs because they’re effectively running a bigger carb deficit throughout their training sessions.


How did I know that link would be to the race-walkers study? 3 weeks to adapt to diet is a joke – designed to fail (perhaps not intentionally, but here we are).

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Ah, yes, the old “it takes longer to adapt” deflection. :roll_eyes:


If the shoe fits…

I’m not going to claim it eventually leads to better performance, but the claim it leads to worse is dubious.

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There are numerous studies showing that low CHO diets impair performance during high intensity exercise, even when followed for months. The only reason the idea is still around us to the cult following that has developed around the people pushing it (e.g., Cordain, Phinney).


I think it does lead to marginally worse performance for even long aerobic efforts, when compared to chronically LFHC, and even close-to-optimal carb fueling during test protocols. Certainly, if carb restriction is part of the intra-test protocol, then a fat adapted group may close that gap.

I suspect the reason many folks anecdotally find that LCHF works well for them is that it manages their sub-optimal carb-fueling problems for them by greatly reducing the chance of hypoglycemia when they invariably consume too few carbs intra-workout or intra-race.

Here’s the authors’ rebuttal piece to your specific claim that a longer duration of LCHF dieting was needed. It appears that may not be true. Same author, 3 yrs later. BURKE 2020, Crisis of Confidence Averted, Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible.pdf (2.0 MB)

It’s a pretty sweet comprehensive piece! 31 pages with awesome figures/tables.

From the article:

For your reference to verify her claims.

Is it weird to anyone else that all the folks promoting fat adaptation / keto are constantly publishing their work in only one journal??

Even in lower-intensity exercise, efficiency of energy production is often reduced.


There’s no point debating with “keto bros”. They’re a cult. No amount of evidence is ever going to change their minds. See also anti vaxers, flat earthers, COVID deniers.

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i haven’t read everything in here, but since a good month i use Lumen to measure my metabolism and the results are not bad, mean very helpfull how your body acts, any of you heard about it or use it?

i am a bit nerdish and interested in science like this! :nerd_face:

So you are likening anyone who chooses not to stuff themselves with carbs at every available opportunity with those fringe groups. Interesting.

No, that’s not what I’m saying.


I looked at one of these but decided against getting one but have have an open mind on it. How do you use it and what benefits do you get from it, if you don’t mind me asking?

Since we have a bunch of smart folks on this thread, and we all love food, curious is anyone is involved with, or is tracking developments in the microbiome / personalized diet / glycemic control research space?

This Cell paper spawned a good deal of interest and at least one company (Day Two) attempting to personalize diets:

The senior authors put out an approachable review paper last year:

There is a brief discussion of ketogenic diet in setting of epilepsy and seizure. Humans and mouse models.

If anyone reading happens to live in Israel, the same group has a project going on to study larger numbers of people:

While we are on this topic, have you heard of Dan Plews and any of his research?
I know he won Kona Age group in 2019, and a proponent on periodized LCHF diet but have not had a chance to read thru his work.


From the article I wrote and linked to previously (Can Fat Adaptation Make You Faster?), summary of my view on that:

When you carb up again, fat-adaptation is quickly lost. Fat adaptation is highly transient. When you start “carbing up” again, you lose the adaptation, regardless of training volume and intensity. The combo of these points means that you either have to be training with reduced intensity and reduced carb-burning machinery in the race prep, or you have to erase your fat adaptation to reap the full benefits of higher carb feeding leading into your race.

Periodized LCHF is still certainly an intriguing idea from a research perspective.

To date, it It has a LONG way to go.

I have seen no applied evidence that it works, to my knowledge, though I have a couple of colleagues who I think are of high intellect and conduct strong research, who think there might be something there and will probably be investigating it in the next decade or so. Tim Podlogar is a good one to follow on twitter/instagram.

Duly noted. Perhaps I still need to heed this lesson.

I am not implying I think anyone here is a cult-follower for full clarity.

I would like to hear that re: Lumen too. Full bias disclosure: I’m skeptical.

Re: Cell Article, linked to by @ DarthShivious, here are their conflict of interest disclosures:
2 out of 3 authors financially benefit from future users of DayTwo. Find an article where the authors aren’t direct investors in the subject

That would be like me publishing a journal article investigating my RP Endurance Macro Calculator (EMC) and finding out that it yields positive results. Surprise! :rofl: