[haspok]

> As you know, carbs are precisely we need when going the distance.

This is completely false. You deplete your carb stores after a few hours (depending on pace etc), and then YOU ARE RUNNING ON KETONES, whether you like it or not. You physically cannot eat and digest enough carbs to sustain your pace for any longer period of time.

Carb depletion can be a real shock for the first time. What happens is that your body is not accustomed to burning fat for energy, and so it just doesn't know what to do.

But if you prepare it will learn how to do it, and do it rather efficiently. Unless you are a pro athlete (in which case you have your own dietician anyway) you will benefit from going keto for long distance endurance sports. Yes, your sprints will be slower, but in exchange you will simply not be hungry, or feel loss of energy (actually, a marathon is not really that long distance, if you are fast enough you won't even deplete your carb stores!).

It takes a few days, maybe a week or two to switch to keto. You can speed up the process by fasting, it will not leave your body any doubt about what is going to happen :) You will feel very weak at first, but this will pass, and then you are in long distance nirvana. You just need to watch out for proper hydration (not too much, not too little) and mineral replenishment. You can even do your sport fasted, it won't make any difference! Highly recommended for those having digestive issues.

As a matter of fact, I'd rather say it is highly irresponsible of anyone doing endurance sports NOT on keto. But as many other things, this is not taught at school, and people have to experiment for themselves to find out what works for them.

[wartijn_]

> This is completely false

No it isn't. The comment to stop eating carbs was aimed at someone who is trying to do a half marathon in less that 2 hours. Like you say yourself this is way to short to deplete your carbs, so to just stop eating carbs seems like exactly the "bad advice that needs a lot of heavy caveats" that the parent poster was talking about.

[haspok]

There are other reasons for going keto even for a half-marathon - and who knows, maybe the full distance is next.

You don't have to worry about timing your meals, or "carb-loading" which is misunderstood and yet done by so many beginners just because they read about it and they disrupt / overload their digestive system, and causes more problems than has benefits (if any - guess how I know that).

I cannot really explain the feeling of not feeling exhausted after a few hours of "exercise" to someone who has not experienced it. Yes, your muscles are sore, yes you are thirsty (an unwanted side-effect of keto - you need to manage hydration!), yet your head is clear, your mind is fresh and you are ready to pounce. You feel like Duracell Bunny.

Is your experience different? I'd be happy to hear about it - maybe it doesn't work so well for everyone?

[scott_w]

You can't even explain your position to me and I ran 23km on Saturday without feeling depleted at all. I regularly bike over 100km without being depleted. I race middle distance triathlons and the only time I run out of energy is when I stop eating carbs.

You're talking absolute nonsense.

[rojeee]

I think OP is referring to people with poor metabolic flexibility. If not fat adapted, then you have enough glycogen for roughly 1600 calories worth of running at which point you bonk and can’t continue. If you are metabolically flexible then you substantially reduce the amount of glycogen you use at the same effort as someone who is not fat adapted. If you are very fat adapted then you can basically continue indefinitely at sub aerobic threshold pace as long as your muscles are strong enough to support you. I also have a low carb diet. It works very well for me. I was metabolically tested and burn roughly 2g of fat per minute at aerobic threshold which is pretty insane. It gets lower as you increase pace as body switches over to glycogen and then anaerobic respiration. People on high carb diets won’t get anywhere near close to that. My Aerobic threshold is >85% of VO2max (anaerobic 95%) and I can keep that up for hours even when apparently glycogen depleted (as restricted carbs in the preceding days). My running has improved immensely since going low carb - run faster with less effort and recover much faster.

Obvs if I’m racing then I use carbs.

[scott_w]

I think that’s different. There are people who can do what you say, eating less carbs, but mostly they’ve been doing that their entire lives. It’s not something you can build a training and fuelling strategy from.

Dylan Johnson does a great dive into fasted training on YouTube, which I’d highly recommend.

[rojeee]

Thanks for the recommendation - will have a listen today.

[rojeee]

I might add that if I’m racing or doing high intensity work, then clearly I take carbs like everyone else.

[banDeveloper]

> You deplete your carb stores after a few hours (depending on pace etc), and then YOU ARE RUNNING ON KETONES, whether you like it or not. You physically cannot eat and digest enough carbs to sustain your pace for any longer period of time.

What do you mean, this is precisely why all professional runners and cyclists consume gels. Not only is it possible to not deplete your carb stores, it's actually pretty easy to keep them from depleting.

> What happens is that your body is not accustomed to burning fat for energy, and so it just doesn't know what to do.

Vast majority of professional cyclists and runners spend majority of their time training in low-instensity zones, where fats are the main source of energy. How then, would they not be accustomed to burning fat for energy?

That's not what happens anyway, the "bonk" is because your body was relying on turning carbs into energy, but the carb stores have depleted. If you try to keep the same effort, your body will be unable to provide sufficient energy to keep you going and you will "bonk". If you were to lower your effort enough for fats to be able to provide sufficient energy, you'd be fine. Anyway, the solution is to consume more carbs, to keep the stores from depleting and no to remove that fuel source entirely.

> Yes, your sprints will be slower, but in exchange you will simply not be hungry, or feel loss of energy.

Sure you won't feel a loss of energy, because you've never had that energy in the first place. I don't understand why you would remove a major fuel source entirely, is there any science behind this?

[haspok]

Pros are pros, but you are not one (are you?), you don't have the experience, the time, the regeneration, the genes, the attitude, the money. So you might as well ignore most of what they do, because you are not one of them.

> Sure you won't feel a loss of energy, because you've never had that energy in the first place. I don't understand why you would remove a major fuel source entirely.

That's a bold statement. Have you ever tried it? Did you have energy?

Imagine that you don't bonk, no matter if you eat or not, and you can still keep roughly the same level of intensity for the entirety of your session, however long it might be. As a matter of fact, you feel just as fresh mentally at the end as at the start. That's why.

[banDeveloper]

Which part do you think applies exclusively to the pros though, I think it applies to everybody. I only used the pros as an example, since they are incentivised to perform at their best and therefore are most likely to apply the best fueling strategies.

> Have you ever tried it?

I have not tried it. Can you provide some sources explaining how it gives any more energy than metabolizing fat does?

> Imagine that you don't bonk, no matter if you eat or not, and you can still keep roughly the same level of intensity for the entirety of your session, however long it might be. As a matter of fact, you feel just as fresh mentally at the end as at the start. That's why.

You don't need to be ketogenic for that though, you just gotta keep it slow. One of my very last outdoor rides last year was like that. 100km ride where I kept it strictly in zone 2. It felt easy and I had a blast. Can't say I felt just as fresh as at the start though.

[scott_w]

To paraphrase a basketball player:

As a trained amateur, I'm much closer to a pro athlete than an untrained person is to me.

And yes, I don't bonk during long runs/rides/etc. because I do the same thing pros do and eat carbs.

[kashyapc]

There is so much misleading "advice" in the above comment that it's not even worth refuting. I just want to warn to others lurking here to be cautious with it.

From the little I know (which is nothing!), going the "keto" route needs a specialist advice[1]. Diet is a charged topic; it would do us good to stay grounded. It's tempting to dole out uninformed advice on the internet. Please resist.

The point you raised at the end is more sensible: people might want to (responsibly and carefully!) try things and see what works for their bodies.

PS: In the past, I wrote here[2] the training routine that worked for me. It also has a link to a "retro" of my previous half-m.

[1] https://www.health.harvard.edu/staying-healthy/should-you-tr...

[2] https://news.ycombinator.com/item?id=33607869

[haspok]

> It's tempting to dole out uninformed advice on the internet.

...says he, and then links to a page of advice on the internet. The "Keto Diet Risks" section on that page is such an epic, "that it's not even worth refuting".

>> Fuzzy thinking and mood swings. "The brain needs sugar from healthy carbohydrates to function. Low-carb diets may cause confusion and irritability,"

This shows that whoever wrote this has never even tried proper keto. Because the brain does not need sugar (otherwise you would die after a few days of fasting), and fuzzy thinking is only for the first couple of days until your body adjusts and your brain gets enough fuel again.

It is in fact quite evil, because if someone starts keto or fasting and feels "confused and irritated" at first, they might just stop doing it out of fear of the unknown. Luckily in our modern society were are past such diseases as type-2 diabetes, right? So nobody should bother checking out something that might actually help with that.

But let me ask about your personal experience with keto or fasting. Did you try either? Did it work for you? I could link a hundred web posts about the benefits of keto, and another hundred about the dangers of it. In fact, anybody could google this for themselves, so I don't find this "I read this and that about something" contributing much to any discussion.

[kashyapc]

[Hi, I am not trying to be confrontational.]

> [...] and then links to a page of advice on the internet [...]

There's a world of difference between an armchair internet-dietitian (no, I'm not implying you are one) and a registered dietitian that is the "director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital" (the author of the said article). It's not appeal to authority—we have to start somewhere. That doesn't mean the said page is 100% accurate.

> But let me ask about your personal experience with keto or fasting [...]

No, I did not try Keto. Yes, I've done fasting before; and yes, it was beneficial. Personally, I'm disciplined with food; almost like a machine, I can happily maintain a healthy diet, without having to "negotiate with myself".

Please note, I'm not denying there are no benefits to Keto or fasting at all. I even recently listened to an episode on Keto on Huberman Lab Podcast to educate myself on it. I don't have personal experience of it, so I refrain to talk about it. Much less use data-points-of-one as a generalization.

[infamousclyde]

> Unless you are a pro athlete (in which case you have your own dietician anyway)

Why not train like a professional athlete and just eat a balanced diet, like their dieticians recommend? My partner has represented my country in the Olympics in a long distance track event and none of her support staff have ever advocated for keto as a responsible diet for her training needs.

I mean, the science says fat is less energy-available than a simple source of carbohydrates. It seems like a pretty easy choice if you want to hit target speeds during your workouts and become faster over time.

[haspok]

> Why not train like a professional athlete and just eat a balanced diet...

Because professional athletes are anything but "balanced". Professional sport is about abusing your body as much as you can possibly get away with, and then some more. For a normal person following a pro's training plans or diet could be the worst thing they could do to their body.

> science says fat is less energy-available than a simple source of carbohydrates

Yes, keto is not a panacea. If you do keto, you will most probably not be the fastest you can be. But you will be unstoppable. If you do carbs, your peak performance should be higher, but for a shorter time. Choose one.

I think what pros (eg. pro cyclists) do is that they try to find the best of both worlds - they train a LOT in lower intensity zones so they get very good at fat burning without actually reaching keto, but they then supplement it with the right type and amount of carbs during races so that they don't lose sprint power. But this is only my theory, I have never been a pro, and never been close to these circles.

[infamousclyde]

> Because professional athletes are anything but "balanced"

I'm sorry, how much money do you think professional runners make that it affords them some crazy diet that the general public can't tolerate? Not even professional runners for that matter-- college runners, or even high schoolers. My partner and all of her colleagues that compete at the international level in Canada have part-time jobs. My partner is in grad school full-time at the moment, too. They aren't "abusing their body" as much as possible, they just do a lot of base mileage, two key workouts a week, and recover and eat properly-- and they've done that for years. That's the secret.

I eat with, and cook for my girlfriend, and I am a brutally normal guy in the military. We just use standard ingredients and try to cook things from scratch. We have pizza and/or go out to eat about once every two weeks or so. This isn't purely anecdotal, it's completely reasonable to run a 120km/wk and maintain a normal life-- that's most elite runners on the field, and I make that assessment as a guy who has been in these circles through my partner.

I would disagree with your assessment of "unstoppable" versus "fastest". You can certainly have both with carbohydrates. Moreover, given the parent comment wanted to get faster, I would probably not reach for keto under your recommendation.

[sasawpg]

> I think what pros (eg. pro cyclists) do is that they try to find the best of both worlds - they train a LOT in lower intensity zones so they get very good at fat burning without actually reaching keto, but they then supplement it with the right type and amount of carbs during races so that they don't lose sprint power. But this is only my theory, I have never been a pro, and never been close to these circles.

You couldn't be further from the truth, especially in a race scenario, not to mention a stage race or a grand tour. Professional (and most well versed) cyclist will pile on carbs in the days leading up to a race, eat a pile the morning of the race and then continue to eat and drink a massive quantity of carbs. It has everything with them being able to replenish what's lost during a race lasting several hours, it is not at all sprint specific. They'll easily aim at 100+ grams of carbs per hour.

I would consider myself a well versed and well trained amateur cyclist. Depending on length of training session and intensity of efforts, I'll aim for 50-100g/hr. In a race my goal is 80-100g/hr from the second the race starts. I've done well enough in multiple 6-9+ hour races and training sessions.

[sdwr]

I want to back this up!

For a while I was carb-reliant, would bring fruit with me to my workouts, felt like I couldn't do more than 30 min of hard effort without fueling.

Made a conscious effort to "go keto", ate more protein and fat, was hungry for 1.5 weeks, but a switch flipped and I can pretty much go forever now. I'm not strict about it anymore, but it definitely unlocked something for me.

I think my sense of exhaustion was coupled with the amount of easy sugar from carbs in my body.. taking the carbs away for a bit broke that dependency.