Back in January of this year I made a significant artimetical error which, combined with the massive confirmation bias from which I suffer, led to the incorrect conclusion that fats require less O2 per ATP than glucose. This is incorrect. They require about 5% more. There are a lot of implications from this in my head and for subsequent posts on the blog. I’ll be working at tidying up follow on-posts but the initial incorrect post is still there to stand as a warning.
Sorry folks, shouldn’t have made the mistake and certainly should have spotted it without help.
With thanks to Mateusz re reworking the arithmetic.
Peter
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13 comments:
Ta
Peter
From the post in question:
"In the comments after a previous post it became pretty obvious that several LC eating folks noted a significant improvement in their ability to breath-hold while running their metabolism on fat rather than on glucose. "
I too noticed this in late summer, when I went swimming for the first time in over a year. I was able to hold my breath and swim the length of the pool (about 32 feet) under water almost as though I had done it all summer. Not a huge athletic feat, but I was surprised.
So the phenomenon still needs an explanation.
Maybe the more fair comparison would be evaluating the O2 per unit ATP hydrolisis yielded by glucose + fatty acids at a certain proportion against a mixture of glucose + fatty acids + ketone bodies, which would better resemble a physiological milieu under carbohydrate or fat burning metabolism....
Breath holding is related to CO2/ATP rather than O2, I have not worked that through the calculation but maybe that decreases under fat burning conditions anyway.
We all make errors. What differs is what one does after the error.
Thanks for setting it straight.
In addition, ATP/O2 would matter most during hypoxia. In that regard, it is expected some metabolic adaptation occur during as result. Some time ago you pointed out uncoupling would be suppressed as result of low ATP
http://high-fat-nutrition.blogspot.com.es/2014/09/uncoupling-control-in-defence-of-ffas.html
(see my comments on that post). Phosphocreatine could help during the first 10 seconds or so (the more you have, the better), after which you either upregulate ketone bodies use (if any, once again the more you have during an ischemic episode, the better) or glucose metabolism (any suggestion on the possible mechanisms suppressing insulin resistance under hypoxia are welcomed). Ketones yield more ATP/O2 -> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3231554/
Hi Bob, the need to breathe is controlled by CO2 pp, not hypoxia. The CO2 differentials between glucose and fat per ATP generated are roughly correct. Hypoxia only becomes a respiratory drive at levels well below what the average person can achieve by swimming underwater. This effect (of reduced CO2) will be real.
karl, ta. Slightly upset here!
Guilliermo, it becomes very difficult to extricate adaptation to fat oxidation with the direct effect of ketones. The push seems to be that the bulk of the effect comes from the ketones but increasing efficiency of ox phos might occur due to mitochondrial biogenesis over a number of weeks in studies studies like Phinney's...
Peter
Just adding to the other comments reporting decreased need to breathe: I too noticed a big decrease while fat-burning. I'd breathe maybe 3 or 4 times per minute with lower amplitude while before that, it would have been 6 or 7 times a minute. I monitor my breathing periodically because I have a condition which can induce renal acidosis (RTA4). Is the decrease just from lower basal metabolism ?
Also: anyone else also notice a lower need for hydration ?
Another random aside, but I've heard you speak in the past about how it's odd that ketogenic diets increase the requirement for sodium, and how it might have something to do with cured meats and people who can tolerate higher sodium being selected for at some point in the past. This makes sense to me, as it would have been our primary means of preservation for a long, long time.
I actually bought some Armour Dried Beef, which has such a high sodium content the vendor actually recommends you wash some of the salt off before using it for cooking. Eating it gave me a sense of just how much salt you have to use to actually genuinely preserve meat, and its a pretty insane amount, roughly 1500 mg for 30g beef. It contains some non-sodium preservatives as well, so people probably used even more historically. I eat like 1-2 servings of it and easily meet my sodium quota for the day.
I also find it interesting that Tibetans who drink Po Cha, aka yak butter tea, add so much salt to the tea that it ends up tasting like sea water to the uninitiated. This makes sense, as drinking a lot of liquid would tend to make you hyponatremic, especially with the added diuretic of the tea, and it probably also helps a lot when it is very cold. Either way, it seems like people who ate a lot of fat or meat, especially in colder climates, would generally be getting a lot of sodium.
jesrad,
I've been puzzled about somewhat reduced thirst for awhile.
Rattus - not only colder climates. People in the more tropical or hotter parts of Australia eat salted prunes as a snack (ugh) or take salt tablets to replace losses from sweat.
Bob, Jesrad - hflc feels calm after the insane thirst of hyperglycaemia.
A Chinese takeaway with rice makes me extremely thirsty wheras Jerky or other salty foods do not. Fast carbs probably take that water and turn it into adiposity? It seems odd on the face of it since carbs are inherently -hydrates.
Another opportunity for some back of the envelope calcs?
That's why we pay you the big money Peter, to cover the cost of envelopes.
:))))
bob, Rattus,
This is all interesting, my condition also causes sodium-wasting, and primal LCHF made the hypovolemic/hyperkalemic crises noticeably more frequent and severe.
I think the reduced thirst could be from less water consumption per ATP produced in the FA oxydation cycles compared to glucose, IIRC beta-oxydation is water-neutral whereas the latter isn't. But it might also be just temporary, as losing sodium makes one slowly get dehydrated without feeling thirsty. I've noticed several people making the transition from HC to LC would sometimes have orthostatic drops in blood pressure. Could be dehydration, or maybe they were "flushing" a lot of potassium from intracellular as they expend glycogen reserves, and their body was still adjusting.
I think I posted a reply to dev.null just now; just to suggest that it is starchy carbs that can drive thirst perhaps via blood sugar peaks.
On the O2 front, I find that taking several deep breaths increases my peripheral temp or the sense of it. Living on air ...
Peter, beta-oxidation requiring more oxygen isn't necessarily a bad thing...
People will look at it as fats being less efficient, but from my viewpoint it seems better to have more oxygen going towards metabolism than hanging around.
I guess what I'm saying is that oxygen is corrosive and harmful, but a necessary evil... and that carbohydrate leaves more oxygen unused, which could be Bad.
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