10 ms·

Running 50km after 82h of fasting

132 points by xavivives 11y ago

tacos 11y ago
I'm not sure if this is pseudoscience or anecdata but I'm sure I could find six doctors saying that this is a horrible idea. From the post: "I couldn’t find any publication about ultra distances and significant amount of fasting." This is not a medical study. This is an individual and could be anything from simply dumb and dangerous to body dysmorphia. Not everything can be safely hacked, friends.
- bosdev 11y ago
  The only fundamental difference between this and a 'proper' scientific experiment is the p value. All scientific experiments have cavets, and all have a probability their finding could be erroneous. Of course, no one should write a textbook based on this one guys self-reported experience. But, assuming he is accurately reporting it, it is evidence that this is _possible_ which is a very important thing to discover. Yes, it may only be possible in 0.01% of the population, that is the type of thing which a larger-scale study can evaluate, but whatever they find, it will be an interesting result which would have been less likely if he hadn't shown it could be done.
  - tacos 11y ago
    Nonsense. A proper scientific experiment would have controls and independent results and medical oversight and calibrated measurement equipment and a clear definition of what's attempting to be proved. This is a guy fooling around and blogging for attention. Dangerously so. p=1, no scientific method = anecdata. His conclusions? Pseudoscience. It's dangerous to him personally and it's damaging to society broadly to promote such without caveats. So I'm providing them.
    - bosdev 11y ago
      He has gathered more data than had he not done it, or not blogged about it. You're right that it doesn't meet any scientific criteria for 'fact' yet, but it is data of a sort, and may be a helpful step on the road to the furtherance of science.
      - reality_czech 11y ago
        Wow. I didn't realize "doing random stuff while taking no measurements, and then later writing about it" qualified as "the furtherance of science." A sample size of 1, combined with an attitude of ignorance and machismo, helps explain why "medical remedies" like bleeding people with leeches and giving them liquid mercury to drink endured for hundreds of years despite no actual evidence that they worked or were safe. Reality check: nutritional deficits lead to cognitive deficits. The Atkins diet is known to lead to heart disease, which Atkins himself died from.
  - exelius 11y ago
    A proper medical study also has doctors monitoring for any risks. They would run blood work and check for anything wrong - it's hard for one person to draw conclusions about how healthy this is if he wasn't baselining and monitoring different vital statistics (liver enzymes, etc.) Also, everyone's body is different: he may just be a genetic freak who is able to do this. Especially with heath/body claims, be very wary that one person's results will be able to transfer to anyone else.
- Rick-Butler 11y ago
  Your point is valid, but your wording could have been better (I assume that is the reason for the down votes). He doesn't mention consulting a doctor to explain the health risks before undertaking this. In my opinion, even if you think a medical professional is going to say you are stupid for trying it, you should still consult a medical professional. You need to be aware of the risks and their signs, and when you post something like this on your blog, it should be prefaced with you probably shouldn't try this. What if someone dies trying to recreate his experiment? (I know common sense etc...)
- Facemelters 11y ago
  This is DEFINITELY not a great idea without pre-clearance from a doctor, and even then it's not great for you. I would imagine this places undue stress on many body systems. Your muscles (and brain!) really really want glucose when you're working this hard. AND he was at altitude. Ketosis workouts DO work very well though. I just don't recommend an Ultra while fasting...
TurboHaskal 11y ago
Author looks like he doesn't even lift. Opinion discarded. PS: To the people scouting his blog. Do yourselves a favor and research catecholamines and the role of stress hormones before taking his advice on performing a single meal a day under what happens to be a caloric deficit scenario. Guy has a long way to go in terms of nutrition and sports performance.
- deleted 11y ago
  [deleted]
- maxerickson 11y ago
  The only "conclusion" presented at the link is that the author successfully completed the race after fasting.
- derptacious 11y ago
  Indeed, he should post his testosterone, cortisol, and adrenaline levels and the time of day they were taken. People who act like this is clear-cut are very silly and have little experience in biology and medicine.
- hanniabu 11y ago
  You can't really expect to find people that look like gym rats doing these types of races.
- powera 11y ago
  I think you're just trolling. http://knowyourmeme.com/memes/do-you-even-lift http://knowyourmeme.com/memes/do-you-even-lift
- e_modad 11y ago
  Do you have any books or posts that you'd recommend looking at? There's a huge mountain of information I'm looking at right now. Any specific leads? I'm genuinely asking because I agree with you but didn't know about any link.
PhrosTT 11y ago
I've seen people die running a half marathon. Please don't push your body to the breaking point just for giggles. Work your way up.
- bosdev 11y ago
  I think you have to think about how those people died. Heat exhaustion? An underlying heart condition? I don't think they died of not having enough nutrients, or not eating soon enough before running.
  - PhrosTT 11y ago
    Yes heat. http://articles.chicagotribune.com/2011-06-04/news/ct-met-half-marathon-heat-0605-20110604_1_long-distance-runner-chicago-half-marathon-spray-stations http://articles.chicagotribune.com/2011-06-04/news/ct-met-ha... I'm just saying the whole "Push through the pain" adage is dangerous.
  - dspillett 11y ago
    Sometimes stroke or similar, caused by incorrect hydration by just drinking lots of plain/plain-ish water which leave various useful things in your body too diluted to be useful. Sometimes an exacerbating factor in heat stroke, so not diagnosed as the heat stroke is seen as the only problem and other causes of heat stroke are assumed. See https://en.wikipedia.org/wiki/Water_intoxication https://en.wikipedia.org/wiki/Water_intoxication
- jimrandomh 11y ago
  Actually seen firsthand, or read about it having happened? (These are very different, because they imply much different prevalence.) The author of the article records a short clip describing how he's feeling at each waypoint, and doesn't seem to have pushed himself terribly hard.
- arnold_palmur 11y ago
  I was watching my fiance run and someone died literally right in front of me at the Brooklyn half-marathon in the fall (he was a young guy - I'd say late 20s). He collapsed right at the finish line and they couldn't revive him. The crazy thing is there was no mention of it after the race or anywhere, I tried googling to find out more info. but nothing. The only info. I found was on /r/running people where people who were also in attendance were talking about it. Marathons just seem so unnatural to me.
maxerickson 11y ago
Related: https://news.ycombinator.com/item?id=10919375 https://news.ycombinator.com/item?id=10919375
exelius 11y ago
While this may be possible, I would worry about the effects on your liver. Ketosis does put additional strain on the liver, and while it doesn't seem like the side effects of extended ketosis are dangerous, there simply aren't any studies on ultra-endurance exercise during ketosis. And while studies on extended exercise during ketosis would be a good thing, they should be performed by researchers and doctors who know what the risks are and can monitor them appropriately. IMO this is dangerous. Just because our hunter-gatherer ancestors did it doesn't mean it's healthy for us. For all we know, this type of activity could wreck your liver and contribute to dying in your 30s (our ancestors did not have a long life expectancy). So even if it was a survival adaptation, it may have ensured the survival of the herd at the cost of the individual.
- maxerickson 11y ago
  I link a small study of endurance athletes performance while in ketosis in another comment.
- bosdev 11y ago
  Please cite your sources. It's certainly possible that it's dangerous, but there is also a tradition of labeling anything which is different than what was historically done as medically dangerous. There is an equal tradition of pulling the medical dangers of various things out of thin air based on guesswork. It is of course possible, I am very interested in reviewing your sources.
- dpark 11y ago
  > our ancestors did not have a long life expectancy Historical life expectancy was skewed because of high childhood mortality. If you look at modern hunter-gatherers, life expectancy is still in the 30s, but life expectancy at age 15 is 54. This is still short by modern standards but everyone isn't/wasn't dying in their 30s. edit: Forgot link to paper: http://www.unm.edu/~hkaplan/KaplanHillLancasterHurtado_2000_LHEvolution.pdf http://www.unm.edu/~hkaplan/KaplanHillLancasterHurtado_2000_...
  - rhinoceraptor 11y ago
weego 11y ago
The whole blog feels like a confused agenda masquerading as hand-wavey pseudo-science. Do not like. Ketosis is really quite well studied at this point, I don't really think this adds anything to the mix. Also why conflate fasting and ketogenics?
- gherkin0 11y ago
  I agree. This guy seems like the type to latch onto weird fitness ideas, the weirder the better, without really understanding what he's doing. His last experiment on his blog was with some system to only sleep 2 hours a day split up into a bunch of naps. > Also why conflate fasting and ketogenics? Isn't fasting basically a ketogenic diet where you are your own food?
  - civilian 11y ago
    Idk, devil's advocate, polyphasic sleep schedule is definitely something to try if you're curious about things. There's a handful of notable people from history who used polyphasic sleep schedules because they felt that it gave them more energy and waking time each day. https://en.wikipedia.org/wiki/Polyphasic_sleep https://en.wikipedia.org/wiki/Polyphasic_sleep At the very least I think we can get behind the idea of a post-lunch afternoon nap, which is a very limited form of polyphasic sleep.
    - gherkin0 11y ago
      Oh, I totally agree. It's just, like most things, you can take it too far. Only sleeping 20 minutes every 4 hours for a total of 2 hours of sleep per day is too far in my book.
- kaonashi 11y ago
  > Also why conflate fasting and ketogenics? He made the distinction between ketosis, a ketosis-inducing diet and fasting as far as I could tell: > I’m suspicious that there are big differences between nutritional ketosis (induced by reducing the intake of high glycemic index foods) and ketosis induced from fasting. In other runs done in nutritional ketosis I didn’t feel that energetic (but it’s hard to compare since I’ve never done it that far in distance). That’s something I may explore.
jordinl 11y ago
I think the most important factor should not be whether you can do it or not, but if you can perform better in ketosis than those who are not in ketosis.
- lamby 11y ago
  In Ironman and related circles it is conceded that performance is decreased, but the reduced calorie requirements in races often mean better results due to less, err, gut complications.
powera 11y ago
Could all the people without medical knowledge please stop saying that their lack-of-medical-knowledge make them smarter than the guy that actually did this? Your requests for various random chemical levels are stupid. We have done science for thousands of years before blood tests were invented.
- ygjb-dupe 11y ago
  Yeah, we did science for thousands of years, but medical science has had (and still has) to contend with pseudo science and snake oil continuously (for a modern take, see homeopathy). An anecdote about a personal experience in relation to an exercise and diet regime doesn't make a person smart, and asking questions about the experience doesn't denigrate the author of the anecdote. Weight loss and nutrition are the bogey man of the health industry, and anyone claiming a new, better way of doing things is inviting harsh criticism - as long as the idea is under attack and not the person, there is no harm done.
  - dang 11y ago
    > Weight loss and nutrition are the bogey man of the health industry They've become a bogeyman of internet forums too. Throw in weight lifting for the trifecta.
joss82 11y ago
Hacking your own body can lead to health issues obviously. But... This may be the way everybody runs in the future. A bit like Cliff Young[1], a potato farmer that won the Sydney-Melbourne ultra-marathon. [1] https://en.wikipedia.org/wiki/Cliff_Young_(athlete) https://en.wikipedia.org/wiki/Cliff_Young_(athlete)
runjake 11y ago
A couple points: * He ran 50 KM in 7 hours and 45 minutes, which amounts to fast walking. In real terms, he probably ran some but probably walked most of it. * If you're going to do something like this, please do it under the supervision of a medical doctor. A 50km isn't a big deal, virtually anyone who can run a marathon can run a 50k, but people do die during this events. Respect the distance. Edit: Here is his Strava entry for the event: https://www.strava.com/activities/morning-run-436423654?utm_campaign=ride_share&utm_content=4091010&utm_medium=widget&utm_source=lab.xavivives.com https://www.strava.com/activities/morning-run-436423654?utm_... From my sloppy napkin math, it looks like he ran the distance (slowly) and probably stopped a lot and had his device configured to pause the time when he stopped. I don't mean to sound down on the guy, he got out there and did 50km. And he specifically mentions he's no athlete. I am glad he documented his experience. But please don't use this as part of any "Couch to 50K" kind of scheme. Ketosis doesn't work like creatine. Edit 2: A metric/imperial conversion pace chart here: https://www.globe-runners.com/sites/default/program_builder_pdf/Metric%20Pace%20Conversion%20Chart.pdf https://www.globe-runners.com/sites/default/program_builder_... Edit 3: pneumatics' comment, below corrects me: "The time spent moving was 5:49. His pace, excluding the time stopped, was 11:12 min/mi. With the elevation gain, this is most definitely running." This is a pretty good performance for a newbie, IMHO. For those saying it's slow, you've either never ran an ultra on rough terrain, or you've been on the cover of running magazines.
- xavivives 11y ago
  I did ran all the way. Surely it wasn't fast, but take in account that there was 2000+ meters of elevation gain.
  - runjake 11y ago
    I found your Strava data and updated my comment. And pfft 2000m+ elevation gain over 50km. Those are gently rolling hills ;-)
  - bluedino 11y ago
    15/min miles make that more of an 8 hour 'walk'
justsomedood 11y ago
My experience in endurance sports is with cycling, and I have a friend that used a "ketosis" diet to help lose some weight. My understanding of the fat burning process is that it can only happen so fast, so with fat as your fuel source you are only able to support moderate intensity levels. This could explain the 7h 45 min minute time for his 50km run (~31 miles). I know if I am riding at race pace for a couple of hours and don't give myself fuel then I am in trouble, but riding at lower intensities I can go for a much longer time without eating as long as I have water.
jessep 11y ago
I applaud the author's spirit of mad science and adventure. As someone with a lot of doctor friends and family, I think it is pretty clear most doctors are not familiar with the relevant research and by default give a cautionary response which merely parrots back the status quo fears, but they're even more risk averse due to malpractice concerns. In terms of getting your blood work done, sure, I'll agree that seems interesting. My father, a doctor, used to be afraid of low carb/ketosis diets, because "bacon, cheese". Years later he read the relevant information and completely switched camps. Finally, self experimentation can be dangerous, sure. But that doesn't mean it isn't valuable and interesting. Do you think people should never do potentially dangerous things in pursuit of adventure, knowledge, truth?
- tacos 11y ago
  Do what you want privately but the value proposition changes when you publish your self-experimentation world-wide. More so when you promote it. And yet more still if and when you try to profit from it. There are clear and common ethical standards here and the blog post comes in well under them.
  - jimrandomh 11y ago
    This is a blog post on the author's personal blog. It doesn't even have ads on it. I really don't see a legitimate objection here. Just take the data for what it is - a report of something one specific person was able to do, which other peoples' physiology might or might not be able to handle, plus some speculation about our distant evolutionary history.
    - tacos 11y ago
      > This is a blog post on the author's personal blog No, the context is now reframed as a post on a highly-influential site, this one. The author is now commenting here, which is great. But "Don't try something like this without at least talking to a doctor, I probably should have" has yet to appear on the post. Therefore I reserve the right to state my objection.
IgorPartola 11y ago
I just started training for my first marathon, and am trying to do some reading on the subject. Hal Higdon's position is I guess what you might call "traditional": your muscles use glycogen as the preferred energy source. Around mile 20 is when most people deplete their glycogen and start burning fat as the primary source of energy, but this is much less efficient, resulting in a performance drop. If this is indeed true, then I guess it means that if your goal is top performance, then carbs are your friend. If your goal is fat loss, then low-carb diet plus long endurance exercise is for you. Does that seem right?
- brianwawok 11y ago
  I think you are conflating two things. Losing weight you do outside of races. Eat less, exercise more - you lose weight. Now during an actual race - do you want to burn sugar or fat? Your body has a TON more fat, even a skinny guy has 50k calories of fat he can burn.. whereas the same guy only has 2k calories of sugar to burn. However burning fat is less efficient, so you are unlikely to set a speed record doing it. An ironman is a 8-16 hour race that burns 5,6,10k calories, and all the successful people I know do it via eating a lot of sugar during the race. In theory you COULD do it off fat, but no one has won a race (that I am aware) doing that, so it seems to not work as well in practice.
  - IgorPartola 11y ago
    OK that makes sense. So then what's the point of doing the fasting + racing thing? Seems like it'll just be very slow and difficult for you to do it.
    - brianwawok 11y ago
      Well in theory you run out of sugar calories after 2000 calories, but you have 50-100k fat calories. If he trains a lot in a fasted state, in theory he would have a much larger bank of energy to draw from. Many animals, for example dogs, mostly burn fat. On the other hand, burning fat is less effecient, so your peak output is lower.
ErikAugust 11y ago
He did it in 7:45. They don't stop the race timer because you stopped. That's towards the back of the pack for a trail 50K with that kind of elevation profile. It'd be better as an experiment if we measured the author's VO2Max, his 1 mile run time on a track, and then ran the 50K on a track. Measure ketone levels, etc.
- xavivives 11y ago
  My resources are limited. But given the chance I won't mind repeating it.
mrits 11y ago
Congrats on not dying I guess. As someone who has been around elite athletes my whole life an article like this doesn't phase me at all. A bad diet can throw the best athlete off her game. On the other hand, Michael Jordan can win the NBA finals on nothing but water and flu in his stomach. There are a lot of factors on what it takes to get through a 50K. I think a lot of us runners could do it starving ourselves, but we'd just feel very bad the whole race.
xavivives 11y ago
I did not see a doctor. Not before, not after. The truth is that even if I had seen one I wouldn't take in account her opinion anyway. The current standards for nutrition are based on a diet rich in carbohydrates. Any response from a doctor (at least the ones I have access to) will discourage this event. It just doesn't fit on their models. Plus they have to play safe. I appreciate all the people who are concern about my health. I'm doing fantastically well. Thanks. I do believe that ketosis is the "default" state for the human being. I have plenty of reasons for that and I'll try to explore more arguments in other posts. Its a very broad subject and I wanted to narrow the scope. I didn't do this experiment out of nowhere. I've been running in ketosis for long time and I know myself pretty well. I've been reading and educating on the subject. I'm not completely stupid. I know the risks and I know there is a lot we don't know about. But if I've done it its because previous runs and experiments gave me the enough confidence. This post doesn't suppose to be a scientific study, not to give any medical advice (I'm taking note from your comments and I'll add a warning). Its just my experience based on what I thing should be a more commmon approach, to focus more on the fundamentals than on a micro view.
- OldSchoolJohnny 11y ago
  Personally I've come around to your point of view. Every week I play a very intense sport consisting of a lot of quick short sprints back and forth for hours and I've self experimented with going the full carb loading route and also the full ketosis for weeks route and repeated a few times over the years. When I play after the low almost no carb eating way I have far more stamina, much greater than people half my age who are playing with me. However I also find it takes a bit longer to warm up and get my wind under low carb but only by a few minutes. I highly encourage anyone to try this out for themselves the difference can be startling.
- vskarine 11y ago
  here is scientific explanation for some of this: http://www.pponline.co.uk/encyc/strength-and-endurance-training-how-athletes-can-maximise-their-performance-42126 http://www.pponline.co.uk/encyc/strength-and-endurance-train... and http://www.pponline.co.uk/encyc/strength-and-endurance-training-can-both-the-elements-be-mastered-at-once-40846# http://www.pponline.co.uk/encyc/strength-and-endurance-train...
petke 11y ago
Ketosis sounds nice and all but it makes ones breath stink bad. I think id rather be fat.
- mahouse 11y ago
  I think the vinegar-scented sweat is even worse...
mmaunder 11y ago
I've played with ketosis. You can verify your body is in a state of ketosis using "keto sticks" that you pee on. They change color and prove that your body is outputting ketones. That's also what causes your breath to smell like something died (my wife's comment). One of the leading thinkers on this is Tim Noakes who has written some excellent literature on the subject and is a keen runner. He became famous for "Lore of Running" which is a tome of a book but is an excellent primer for any runner serious about nutrition and metabolic processes. Noakes has more recently joined the low carb/low GI movement and has some pretty radical thinking in the area. I would also echo some other commenters here that Ketosis is IMHO not a healthy state and can have quite far reaching health consequences. One of the by products of ketosis is acetone which is what makes your breath smell - so there are some fairly radical changes in your body's chemical functioning as it goes into starvation and survival mode. I tend to gravitate away from radical experiments like this and more towards what the leading edge professional athletes are doing, minus the steroids. They have plenty of motivation to innovate in the field in a sustainable way.
- omegaworks 11y ago
  >I would also echo some other commenters here that Ketosis is IMHO not a healthy state and can have quite far reaching health consequences. Are you a doctor? Are you qualified in any way to be giving health recommendations? No? Parroting the crowd doesn't help people. Especially people with insulin sensitivities that could absolutely be helped by a low carbohydrate diet.[0] 0: [pdf link] http://download.springer.com/static/pdf/335/art%253A10.1186%252F1743-7075-5-36.pdf?originUrl=http%3A%2F%2Fnutritionandmetabolism.biomedcentral.com%2Farticle%2F10.1186%2F1743-7075-5-36&token2=exp=1453230799~acl=%2Fstatic%2Fpdf%2F335%2Fart%25253A10.1186%25252F1743-7075-5-36.pdf*~hmac=172c78145b30e0ebe1bf1985636da0eadc1d5f12ffd5aaf8a5164a15d7e87b5f http://download.springer.com/static/pdf/335/art%253A10.1186%...
- skrause 11y ago
  > so there are some fairly radical changes in your body's chemical functioning as it goes into starvation and survival mode. Ketosis is not a "starvation mode", it's just one of the normal ways your body provides energy. During most of human history people didn't have plenty of carbs available all day long, so ketosis was most likely the normal state and not an exception. "Starvation mode" because of eating less is generally just a myth and an excuse for people why their diet failed.
folli 11y ago
For a community of 'hackers' (which I assume should embrace trying out new things and questioning traditional values), the majority of these comments sound very negative and not constructive.
acconrad 11y ago
Funny that this gets upvoted so high and a more reasonable article that was posted in the same day (https://news.ycombinator.com/item?id=10931349 https://news.ycombinator.com/item?id=10931349) did not. I've done ketosis, high carb, and moderate carb, and the fact is that while ketosis can work for some, it can be damaging to others. I tried keto for a while and it raised my fasting blood glucose levels to pre-diabetic levels. As soon as I went back to a moderate carb intake, my blood glucose was back to near-ideal. Obviously you should take further tests (HbA1C) to be absolutely sure if you're at risk, but it's not all smiles and rainbows for keto, you really need to make sure your body can actually adapt properly to the changes that are going on in your body as a result of the diet that promotes keto.
- terio 11y ago
  I've had a similar experience. I researched that and found that in those conditions having a fasting glucose that is higher than the "normal" range is not a problem, just an adaptation. I had HbA1C done several times and the results came back perfect.
- nswanberg 11y ago
  More people find articles discussing what is possible more interesting than a summary article. Xavi was interested in ketosis, read about the subject, saw that runners like Tim Olsen had done well on a paleo-type diet and wondered about long-distance running in ketosis, followed through on the experiment, and wrote it up. To me that is the ideal thing to post here.
matt_wulfeck 11y ago
I'd like to add my own data points for low-carb/ketosis and exercise. In the beginning it was very hard and I felt extremely lethargic (typically 3 to 4 days after switching to < 30g carbs a day). My exercise at the time was 2 miles on the treadmill and 20 minutes of full body weight lifting (squats, etc). The worse I ever felt was during that time (3-4 days in). After that I would slowly improve and within a few weeks could almost reach my normal max, though never exceeded them. The bonus part was that I was melting off pounds of fat. This was just my experience. I found that salty drinks (such as chicken stock) helped a lot when first beginning low carb to prevent the lethargic feeling ~3 days in.
merpnderp 11y ago
I know the 4 months I went on low/no carbs, I had never felt better, had more energy, or lost weight faster. I lost 43lbs, saw my cholesterol and triglycerides go from marginal to perfect, and ate as much as I wanted. Course then my gallbladder stopped pumping and I haven't tried it again, although I don't see why I couldn't.
JeremyNT 11y ago
Certainly an interesting experiment. As somebody who only engages in "moderate" endurance activities (bicycle rides ~100 miles) I can relate the difference diet makes for me on long activities. Endurance athletes speak of a thing called the "bonk"[0] - a point beyond which continued activity becomes much more difficult. This state is due to the exhaustion of glycogen stores in the body. I've encountered this only a few times, but it's a really interesting phenomenon. In times I do not prepare well enough, I just run out of "energy." Everything gets harder, and I don't recover from it. It's not the case that I cannot continue, but continued exertion feels much more difficult. I feel mental fatigue as well, and I have felt "light headed" in this state. This is why it is recommended to consume carbohydrates when engaging in endurance activities. It's not that you can't continue on ketosis, it's that you continue in a very suboptimal manner, and in something like cycling (where you are moving quite quickly) a sensation of light-headedness can be exceptionally dangerous. Incidentally, the rate of depletion of glycogen stores is relative to the intensity of the activity. Operating further below the aerobic threshold will allow one to deplete the glycogen stores more slowly. If the OP is in good shape, this probably played a role in his success, as he might be running at a less intense pace than he would be capable of were he consuming carbohydrates. [0] https://en.wikipedia.org/wiki/Hitting_the_wall https://en.wikipedia.org/wiki/Hitting_the_wall
sshbio 11y ago
«And they were hunting because didn’t have food in the first place…» I laughed at this one.
cafard 11y ago
Not something I would try, or would have tried at what I suppose is his age. I will say a runner in training can get into ketosis with no need for fasting--visiting the downwind side of marathon finish chutes would probably convince you of this. I did "hit the wall" a couple of times, but my diet leading up to the race was no different from that before other races. In one case it was inadequate training. In a couple of others it was setting out at too fast a pace. Now, that is not to say that I felt good in the others--I felt awful but bearably awful.
kazinator 11y ago
I once tried just 16 miles after just 36 hours of fasting. It was interesting. I don't remember a whole lot, other than that it was a serene kind of experience. I was in quite a different mental state from the run-of-the mill run.

132 points by xavivives 11y ago

tacos 11y ago

I'm not sure if this is pseudoscience or anecdata but I'm sure I could find six doctors saying that this is a horrible idea. From the post: "I couldn’t find any publication about ultra distances and significant amount of fasting." This is not a medical study. This is an individual and could be anything from simply dumb and dangerous to body dysmorphia. Not everything can be safely hacked, friends.

bosdev 11y ago
The only fundamental difference between this and a 'proper' scientific experiment is the p value. All scientific experiments have cavets, and all have a probability their finding could be erroneous. Of course, no one should write a textbook based on this one guys self-reported experience. But, assuming he is accurately reporting it, it is evidence that this is _possible_ which is a very important thing to discover. Yes, it may only be possible in 0.01% of the population, that is the type of thing which a larger-scale study can evaluate, but whatever they find, it will be an interesting result which would have been less likely if he hadn't shown it could be done.
- tacos 11y ago
  Nonsense. A proper scientific experiment would have controls and independent results and medical oversight and calibrated measurement equipment and a clear definition of what's attempting to be proved. This is a guy fooling around and blogging for attention. Dangerously so. p=1, no scientific method = anecdata. His conclusions? Pseudoscience. It's dangerous to him personally and it's damaging to society broadly to promote such without caveats. So I'm providing them.
  - bosdev 11y ago
    He has gathered more data than had he not done it, or not blogged about it. You're right that it doesn't meet any scientific criteria for 'fact' yet, but it is data of a sort, and may be a helpful step on the road to the furtherance of science.
    - reality_czech 11y ago
      Wow. I didn't realize "doing random stuff while taking no measurements, and then later writing about it" qualified as "the furtherance of science." A sample size of 1, combined with an attitude of ignorance and machismo, helps explain why "medical remedies" like bleeding people with leeches and giving them liquid mercury to drink endured for hundreds of years despite no actual evidence that they worked or were safe. Reality check: nutritional deficits lead to cognitive deficits. The Atkins diet is known to lead to heart disease, which Atkins himself died from.
- exelius 11y ago
  A proper medical study also has doctors monitoring for any risks. They would run blood work and check for anything wrong - it's hard for one person to draw conclusions about how healthy this is if he wasn't baselining and monitoring different vital statistics (liver enzymes, etc.) Also, everyone's body is different: he may just be a genetic freak who is able to do this. Especially with heath/body claims, be very wary that one person's results will be able to transfer to anyone else.
Rick-Butler 11y ago
Your point is valid, but your wording could have been better (I assume that is the reason for the down votes). He doesn't mention consulting a doctor to explain the health risks before undertaking this. In my opinion, even if you think a medical professional is going to say you are stupid for trying it, you should still consult a medical professional. You need to be aware of the risks and their signs, and when you post something like this on your blog, it should be prefaced with you probably shouldn't try this. What if someone dies trying to recreate his experiment? (I know common sense etc...)
Facemelters 11y ago
This is DEFINITELY not a great idea without pre-clearance from a doctor, and even then it's not great for you. I would imagine this places undue stress on many body systems. Your muscles (and brain!) really really want glucose when you're working this hard. AND he was at altitude. Ketosis workouts DO work very well though. I just don't recommend an Ultra while fasting...

TurboHaskal 11y ago

Author looks like he doesn't even lift. Opinion discarded. PS: To the people scouting his blog. Do yourselves a favor and research catecholamines and the role of stress hormones before taking his advice on performing a single meal a day under what happens to be a caloric deficit scenario. Guy has a long way to go in terms of nutrition and sports performance.

deleted 11y ago
[deleted]
maxerickson 11y ago
The only "conclusion" presented at the link is that the author successfully completed the race after fasting.
derptacious 11y ago
Indeed, he should post his testosterone, cortisol, and adrenaline levels and the time of day they were taken. People who act like this is clear-cut are very silly and have little experience in biology and medicine.
hanniabu 11y ago
You can't really expect to find people that look like gym rats doing these types of races.
powera 11y ago
I think you're just trolling. http://knowyourmeme.com/memes/do-you-even-lift http://knowyourmeme.com/memes/do-you-even-lift
e_modad 11y ago
Do you have any books or posts that you'd recommend looking at? There's a huge mountain of information I'm looking at right now. Any specific leads? I'm genuinely asking because I agree with you but didn't know about any link.

PhrosTT 11y ago

I've seen people die running a half marathon. Please don't push your body to the breaking point just for giggles. Work your way up.

bosdev 11y ago
I think you have to think about how those people died. Heat exhaustion? An underlying heart condition? I don't think they died of not having enough nutrients, or not eating soon enough before running.
- PhrosTT 11y ago
  Yes heat. http://articles.chicagotribune.com/2011-06-04/news/ct-met-half-marathon-heat-0605-20110604_1_long-distance-runner-chicago-half-marathon-spray-stations http://articles.chicagotribune.com/2011-06-04/news/ct-met-ha... I'm just saying the whole "Push through the pain" adage is dangerous.
- dspillett 11y ago
  Sometimes stroke or similar, caused by incorrect hydration by just drinking lots of plain/plain-ish water which leave various useful things in your body too diluted to be useful. Sometimes an exacerbating factor in heat stroke, so not diagnosed as the heat stroke is seen as the only problem and other causes of heat stroke are assumed. See https://en.wikipedia.org/wiki/Water_intoxication https://en.wikipedia.org/wiki/Water_intoxication
jimrandomh 11y ago
Actually seen firsthand, or read about it having happened? (These are very different, because they imply much different prevalence.) The author of the article records a short clip describing how he's feeling at each waypoint, and doesn't seem to have pushed himself terribly hard.
arnold_palmur 11y ago
I was watching my fiance run and someone died literally right in front of me at the Brooklyn half-marathon in the fall (he was a young guy - I'd say late 20s). He collapsed right at the finish line and they couldn't revive him. The crazy thing is there was no mention of it after the race or anywhere, I tried googling to find out more info. but nothing. The only info. I found was on /r/running people where people who were also in attendance were talking about it. Marathons just seem so unnatural to me.

maxerickson 11y ago

Related: https://news.ycombinator.com/item?id=10919375 https://news.ycombinator.com/item?id=10919375

exelius 11y ago

While this may be possible, I would worry about the effects on your liver. Ketosis does put additional strain on the liver, and while it doesn't seem like the side effects of extended ketosis are dangerous, there simply aren't any studies on ultra-endurance exercise during ketosis. And while studies on extended exercise during ketosis would be a good thing, they should be performed by researchers and doctors who know what the risks are and can monitor them appropriately. IMO this is dangerous. Just because our hunter-gatherer ancestors did it doesn't mean it's healthy for us. For all we know, this type of activity could wreck your liver and contribute to dying in your 30s (our ancestors did not have a long life expectancy). So even if it was a survival adaptation, it may have ensured the survival of the herd at the cost of the individual.

maxerickson 11y ago
I link a small study of endurance athletes performance while in ketosis in another comment.
bosdev 11y ago
Please cite your sources. It's certainly possible that it's dangerous, but there is also a tradition of labeling anything which is different than what was historically done as medically dangerous. There is an equal tradition of pulling the medical dangers of various things out of thin air based on guesswork. It is of course possible, I am very interested in reviewing your sources.
dpark 11y ago
> our ancestors did not have a long life expectancy Historical life expectancy was skewed because of high childhood mortality. If you look at modern hunter-gatherers, life expectancy is still in the 30s, but life expectancy at age 15 is 54. This is still short by modern standards but everyone isn't/wasn't dying in their 30s. edit: Forgot link to paper: http://www.unm.edu/~hkaplan/KaplanHillLancasterHurtado_2000_LHEvolution.pdf http://www.unm.edu/~hkaplan/KaplanHillLancasterHurtado_2000_...
- rhinoceraptor 11y ago

weego 11y ago

The whole blog feels like a confused agenda masquerading as hand-wavey pseudo-science. Do not like. Ketosis is really quite well studied at this point, I don't really think this adds anything to the mix. Also why conflate fasting and ketogenics?

gherkin0 11y ago
I agree. This guy seems like the type to latch onto weird fitness ideas, the weirder the better, without really understanding what he's doing. His last experiment on his blog was with some system to only sleep 2 hours a day split up into a bunch of naps. > Also why conflate fasting and ketogenics? Isn't fasting basically a ketogenic diet where you are your own food?
- civilian 11y ago
  Idk, devil's advocate, polyphasic sleep schedule is definitely something to try if you're curious about things. There's a handful of notable people from history who used polyphasic sleep schedules because they felt that it gave them more energy and waking time each day. https://en.wikipedia.org/wiki/Polyphasic_sleep https://en.wikipedia.org/wiki/Polyphasic_sleep At the very least I think we can get behind the idea of a post-lunch afternoon nap, which is a very limited form of polyphasic sleep.
  - gherkin0 11y ago
    Oh, I totally agree. It's just, like most things, you can take it too far. Only sleeping 20 minutes every 4 hours for a total of 2 hours of sleep per day is too far in my book.
kaonashi 11y ago
> Also why conflate fasting and ketogenics? He made the distinction between ketosis, a ketosis-inducing diet and fasting as far as I could tell: > I’m suspicious that there are big differences between nutritional ketosis (induced by reducing the intake of high glycemic index foods) and ketosis induced from fasting. In other runs done in nutritional ketosis I didn’t feel that energetic (but it’s hard to compare since I’ve never done it that far in distance). That’s something I may explore.

jordinl 11y ago

I think the most important factor should not be whether you can do it or not, but if you can perform better in ketosis than those who are not in ketosis.

lamby 11y ago
In Ironman and related circles it is conceded that performance is decreased, but the reduced calorie requirements in races often mean better results due to less, err, gut complications.

powera 11y ago

Could all the people without medical knowledge please stop saying that their lack-of-medical-knowledge make them smarter than the guy that actually did this? Your requests for various random chemical levels are stupid. We have done science for thousands of years before blood tests were invented.

ygjb-dupe 11y ago
Yeah, we did science for thousands of years, but medical science has had (and still has) to contend with pseudo science and snake oil continuously (for a modern take, see homeopathy). An anecdote about a personal experience in relation to an exercise and diet regime doesn't make a person smart, and asking questions about the experience doesn't denigrate the author of the anecdote. Weight loss and nutrition are the bogey man of the health industry, and anyone claiming a new, better way of doing things is inviting harsh criticism - as long as the idea is under attack and not the person, there is no harm done.
- dang 11y ago
  > Weight loss and nutrition are the bogey man of the health industry They've become a bogeyman of internet forums too. Throw in weight lifting for the trifecta.

joss82 11y ago

Hacking your own body can lead to health issues obviously. But... This may be the way everybody runs in the future. A bit like Cliff Young[1], a potato farmer that won the Sydney-Melbourne ultra-marathon. [1] https://en.wikipedia.org/wiki/Cliff_Young_(athlete) https://en.wikipedia.org/wiki/Cliff_Young_(athlete)

runjake 11y ago

A couple points: * He ran 50 KM in 7 hours and 45 minutes, which amounts to fast walking. In real terms, he probably ran some but probably walked most of it. * If you're going to do something like this, please do it under the supervision of a medical doctor. A 50km isn't a big deal, virtually anyone who can run a marathon can run a 50k, but people do die during this events. Respect the distance. Edit: Here is his Strava entry for the event: https://www.strava.com/activities/morning-run-436423654?utm_campaign=ride_share&utm_content=4091010&utm_medium=widget&utm_source=lab.xavivives.com https://www.strava.com/activities/morning-run-436423654?utm_... From my sloppy napkin math, it looks like he ran the distance (slowly) and probably stopped a lot and had his device configured to pause the time when he stopped. I don't mean to sound down on the guy, he got out there and did 50km. And he specifically mentions he's no athlete. I am glad he documented his experience. But please don't use this as part of any "Couch to 50K" kind of scheme. Ketosis doesn't work like creatine. Edit 2: A metric/imperial conversion pace chart here: https://www.globe-runners.com/sites/default/program_builder_pdf/Metric%20Pace%20Conversion%20Chart.pdf https://www.globe-runners.com/sites/default/program_builder_... Edit 3: pneumatics' comment, below corrects me: "The time spent moving was 5:49. His pace, excluding the time stopped, was 11:12 min/mi. With the elevation gain, this is most definitely running." This is a pretty good performance for a newbie, IMHO. For those saying it's slow, you've either never ran an ultra on rough terrain, or you've been on the cover of running magazines.

xavivives 11y ago
I did ran all the way. Surely it wasn't fast, but take in account that there was 2000+ meters of elevation gain.
- runjake 11y ago
  I found your Strava data and updated my comment. And pfft 2000m+ elevation gain over 50km. Those are gently rolling hills ;-)
- bluedino 11y ago
  15/min miles make that more of an 8 hour 'walk'

justsomedood 11y ago

My experience in endurance sports is with cycling, and I have a friend that used a "ketosis" diet to help lose some weight. My understanding of the fat burning process is that it can only happen so fast, so with fat as your fuel source you are only able to support moderate intensity levels. This could explain the 7h 45 min minute time for his 50km run (~31 miles). I know if I am riding at race pace for a couple of hours and don't give myself fuel then I am in trouble, but riding at lower intensities I can go for a much longer time without eating as long as I have water.

jessep 11y ago

I applaud the author's spirit of mad science and adventure. As someone with a lot of doctor friends and family, I think it is pretty clear most doctors are not familiar with the relevant research and by default give a cautionary response which merely parrots back the status quo fears, but they're even more risk averse due to malpractice concerns. In terms of getting your blood work done, sure, I'll agree that seems interesting. My father, a doctor, used to be afraid of low carb/ketosis diets, because "bacon, cheese". Years later he read the relevant information and completely switched camps. Finally, self experimentation can be dangerous, sure. But that doesn't mean it isn't valuable and interesting. Do you think people should never do potentially dangerous things in pursuit of adventure, knowledge, truth?

tacos 11y ago
Do what you want privately but the value proposition changes when you publish your self-experimentation world-wide. More so when you promote it. And yet more still if and when you try to profit from it. There are clear and common ethical standards here and the blog post comes in well under them.
- jimrandomh 11y ago
  This is a blog post on the author's personal blog. It doesn't even have ads on it. I really don't see a legitimate objection here. Just take the data for what it is - a report of something one specific person was able to do, which other peoples' physiology might or might not be able to handle, plus some speculation about our distant evolutionary history.
  - tacos 11y ago
    > This is a blog post on the author's personal blog No, the context is now reframed as a post on a highly-influential site, this one. The author is now commenting here, which is great. But "Don't try something like this without at least talking to a doctor, I probably should have" has yet to appear on the post. Therefore I reserve the right to state my objection.

IgorPartola 11y ago

I just started training for my first marathon, and am trying to do some reading on the subject. Hal Higdon's position is I guess what you might call "traditional": your muscles use glycogen as the preferred energy source. Around mile 20 is when most people deplete their glycogen and start burning fat as the primary source of energy, but this is much less efficient, resulting in a performance drop. If this is indeed true, then I guess it means that if your goal is top performance, then carbs are your friend. If your goal is fat loss, then low-carb diet plus long endurance exercise is for you. Does that seem right?

brianwawok 11y ago
I think you are conflating two things. Losing weight you do outside of races. Eat less, exercise more - you lose weight. Now during an actual race - do you want to burn sugar or fat? Your body has a TON more fat, even a skinny guy has 50k calories of fat he can burn.. whereas the same guy only has 2k calories of sugar to burn. However burning fat is less efficient, so you are unlikely to set a speed record doing it. An ironman is a 8-16 hour race that burns 5,6,10k calories, and all the successful people I know do it via eating a lot of sugar during the race. In theory you COULD do it off fat, but no one has won a race (that I am aware) doing that, so it seems to not work as well in practice.
- IgorPartola 11y ago
  OK that makes sense. So then what's the point of doing the fasting + racing thing? Seems like it'll just be very slow and difficult for you to do it.
  - brianwawok 11y ago
    Well in theory you run out of sugar calories after 2000 calories, but you have 50-100k fat calories. If he trains a lot in a fasted state, in theory he would have a much larger bank of energy to draw from. Many animals, for example dogs, mostly burn fat. On the other hand, burning fat is less effecient, so your peak output is lower.

ErikAugust 11y ago

He did it in 7:45. They don't stop the race timer because you stopped. That's towards the back of the pack for a trail 50K with that kind of elevation profile. It'd be better as an experiment if we measured the author's VO2Max, his 1 mile run time on a track, and then ran the 50K on a track. Measure ketone levels, etc.

xavivives 11y ago
My resources are limited. But given the chance I won't mind repeating it.

mrits 11y ago

Congrats on not dying I guess. As someone who has been around elite athletes my whole life an article like this doesn't phase me at all. A bad diet can throw the best athlete off her game. On the other hand, Michael Jordan can win the NBA finals on nothing but water and flu in his stomach. There are a lot of factors on what it takes to get through a 50K. I think a lot of us runners could do it starving ourselves, but we'd just feel very bad the whole race.

xavivives 11y ago

I did not see a doctor. Not before, not after. The truth is that even if I had seen one I wouldn't take in account her opinion anyway. The current standards for nutrition are based on a diet rich in carbohydrates. Any response from a doctor (at least the ones I have access to) will discourage this event. It just doesn't fit on their models. Plus they have to play safe. I appreciate all the people who are concern about my health. I'm doing fantastically well. Thanks. I do believe that ketosis is the "default" state for the human being. I have plenty of reasons for that and I'll try to explore more arguments in other posts. Its a very broad subject and I wanted to narrow the scope. I didn't do this experiment out of nowhere. I've been running in ketosis for long time and I know myself pretty well. I've been reading and educating on the subject. I'm not completely stupid. I know the risks and I know there is a lot we don't know about. But if I've done it its because previous runs and experiments gave me the enough confidence. This post doesn't suppose to be a scientific study, not to give any medical advice (I'm taking note from your comments and I'll add a warning). Its just my experience based on what I thing should be a more commmon approach, to focus more on the fundamentals than on a micro view.

OldSchoolJohnny 11y ago
Personally I've come around to your point of view. Every week I play a very intense sport consisting of a lot of quick short sprints back and forth for hours and I've self experimented with going the full carb loading route and also the full ketosis for weeks route and repeated a few times over the years. When I play after the low almost no carb eating way I have far more stamina, much greater than people half my age who are playing with me. However I also find it takes a bit longer to warm up and get my wind under low carb but only by a few minutes. I highly encourage anyone to try this out for themselves the difference can be startling.
vskarine 11y ago
here is scientific explanation for some of this: http://www.pponline.co.uk/encyc/strength-and-endurance-training-how-athletes-can-maximise-their-performance-42126 http://www.pponline.co.uk/encyc/strength-and-endurance-train... and http://www.pponline.co.uk/encyc/strength-and-endurance-training-can-both-the-elements-be-mastered-at-once-40846# http://www.pponline.co.uk/encyc/strength-and-endurance-train...

petke 11y ago

Ketosis sounds nice and all but it makes ones breath stink bad. I think id rather be fat.

mahouse 11y ago
I think the vinegar-scented sweat is even worse...

mmaunder 11y ago

I've played with ketosis. You can verify your body is in a state of ketosis using "keto sticks" that you pee on. They change color and prove that your body is outputting ketones. That's also what causes your breath to smell like something died (my wife's comment). One of the leading thinkers on this is Tim Noakes who has written some excellent literature on the subject and is a keen runner. He became famous for "Lore of Running" which is a tome of a book but is an excellent primer for any runner serious about nutrition and metabolic processes. Noakes has more recently joined the low carb/low GI movement and has some pretty radical thinking in the area. I would also echo some other commenters here that Ketosis is IMHO not a healthy state and can have quite far reaching health consequences. One of the by products of ketosis is acetone which is what makes your breath smell - so there are some fairly radical changes in your body's chemical functioning as it goes into starvation and survival mode. I tend to gravitate away from radical experiments like this and more towards what the leading edge professional athletes are doing, minus the steroids. They have plenty of motivation to innovate in the field in a sustainable way.

omegaworks 11y ago
>I would also echo some other commenters here that Ketosis is IMHO not a healthy state and can have quite far reaching health consequences. Are you a doctor? Are you qualified in any way to be giving health recommendations? No? Parroting the crowd doesn't help people. Especially people with insulin sensitivities that could absolutely be helped by a low carbohydrate diet.[0] 0: [pdf link] http://download.springer.com/static/pdf/335/art%253A10.1186%252F1743-7075-5-36.pdf?originUrl=http%3A%2F%2Fnutritionandmetabolism.biomedcentral.com%2Farticle%2F10.1186%2F1743-7075-5-36&token2=exp=1453230799~acl=%2Fstatic%2Fpdf%2F335%2Fart%25253A10.1186%25252F1743-7075-5-36.pdf*~hmac=172c78145b30e0ebe1bf1985636da0eadc1d5f12ffd5aaf8a5164a15d7e87b5f http://download.springer.com/static/pdf/335/art%253A10.1186%...
skrause 11y ago
> so there are some fairly radical changes in your body's chemical functioning as it goes into starvation and survival mode. Ketosis is not a "starvation mode", it's just one of the normal ways your body provides energy. During most of human history people didn't have plenty of carbs available all day long, so ketosis was most likely the normal state and not an exception. "Starvation mode" because of eating less is generally just a myth and an excuse for people why their diet failed.

folli 11y ago

For a community of 'hackers' (which I assume should embrace trying out new things and questioning traditional values), the majority of these comments sound very negative and not constructive.

acconrad 11y ago

Funny that this gets upvoted so high and a more reasonable article that was posted in the same day (https://news.ycombinator.com/item?id=10931349 https://news.ycombinator.com/item?id=10931349) did not. I've done ketosis, high carb, and moderate carb, and the fact is that while ketosis can work for some, it can be damaging to others. I tried keto for a while and it raised my fasting blood glucose levels to pre-diabetic levels. As soon as I went back to a moderate carb intake, my blood glucose was back to near-ideal. Obviously you should take further tests (HbA1C) to be absolutely sure if you're at risk, but it's not all smiles and rainbows for keto, you really need to make sure your body can actually adapt properly to the changes that are going on in your body as a result of the diet that promotes keto.

terio 11y ago
I've had a similar experience. I researched that and found that in those conditions having a fasting glucose that is higher than the "normal" range is not a problem, just an adaptation. I had HbA1C done several times and the results came back perfect.
nswanberg 11y ago
More people find articles discussing what is possible more interesting than a summary article. Xavi was interested in ketosis, read about the subject, saw that runners like Tim Olsen had done well on a paleo-type diet and wondered about long-distance running in ketosis, followed through on the experiment, and wrote it up. To me that is the ideal thing to post here.

matt_wulfeck 11y ago

I'd like to add my own data points for low-carb/ketosis and exercise. In the beginning it was very hard and I felt extremely lethargic (typically 3 to 4 days after switching to < 30g carbs a day). My exercise at the time was 2 miles on the treadmill and 20 minutes of full body weight lifting (squats, etc). The worse I ever felt was during that time (3-4 days in). After that I would slowly improve and within a few weeks could almost reach my normal max, though never exceeded them. The bonus part was that I was melting off pounds of fat. This was just my experience. I found that salty drinks (such as chicken stock) helped a lot when first beginning low carb to prevent the lethargic feeling ~3 days in.

merpnderp 11y ago

I know the 4 months I went on low/no carbs, I had never felt better, had more energy, or lost weight faster. I lost 43lbs, saw my cholesterol and triglycerides go from marginal to perfect, and ate as much as I wanted. Course then my gallbladder stopped pumping and I haven't tried it again, although I don't see why I couldn't.

JeremyNT 11y ago

Certainly an interesting experiment. As somebody who only engages in "moderate" endurance activities (bicycle rides ~100 miles) I can relate the difference diet makes for me on long activities. Endurance athletes speak of a thing called the "bonk"[0] - a point beyond which continued activity becomes much more difficult. This state is due to the exhaustion of glycogen stores in the body. I've encountered this only a few times, but it's a really interesting phenomenon. In times I do not prepare well enough, I just run out of "energy." Everything gets harder, and I don't recover from it. It's not the case that I cannot continue, but continued exertion feels much more difficult. I feel mental fatigue as well, and I have felt "light headed" in this state. This is why it is recommended to consume carbohydrates when engaging in endurance activities. It's not that you can't continue on ketosis, it's that you continue in a very suboptimal manner, and in something like cycling (where you are moving quite quickly) a sensation of light-headedness can be exceptionally dangerous. Incidentally, the rate of depletion of glycogen stores is relative to the intensity of the activity. Operating further below the aerobic threshold will allow one to deplete the glycogen stores more slowly. If the OP is in good shape, this probably played a role in his success, as he might be running at a less intense pace than he would be capable of were he consuming carbohydrates. [0] https://en.wikipedia.org/wiki/Hitting_the_wall https://en.wikipedia.org/wiki/Hitting_the_wall

sshbio 11y ago

«And they were hunting because didn’t have food in the first place…» I laughed at this one.

cafard 11y ago

Not something I would try, or would have tried at what I suppose is his age. I will say a runner in training can get into ketosis with no need for fasting--visiting the downwind side of marathon finish chutes would probably convince you of this. I did "hit the wall" a couple of times, but my diet leading up to the race was no different from that before other races. In one case it was inadequate training. In a couple of others it was setting out at too fast a pace. Now, that is not to say that I felt good in the others--I felt awful but bearably awful.

kazinator 11y ago

I once tried just 16 miles after just 36 hours of fasting. It was interesting. I don't remember a whole lot, other than that it was a serene kind of experience. I was in quite a different mental state from the run-of-the mill run.