[exelius]

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.

[dpark]

> 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_...

[rhinoceraptor]

Also, our life expectancy is increased even further due to modern medicine. But that isn't a validation of modern diet and lifestyle, we're just really good at stuff like fixing broken arms and treating infections.

[omegaworks]

>Ketosis does put additional strain on the liver

Do you know what you're talking about? Fructose metabolism and alcohol metabolism also occur in the liver.

Keto reverses non-alcoholic fatty liver disease http://link.springer.com/article/10.1007/s10620-006-9433-5

Many tissues can use ketones directly as fuel. https://en.wikipedia.org/wiki/Ketone_bodies#Uses_in_the_hear...

[bosdev]

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.

[maxerickson]

I link a small study of endurance athletes performance while in ketosis in another comment.