Not to cut you guys from a very interesting discussion but we've kinda moved away from the initial question without really finding an answer.
It seems that neither fasting nor a ketogenic diet can ''cure'' cancer once it's diagnosable.
A ketogenic diet may significantly slow down tumor growth in some type of cancers; brain,prostate... however it seems and based on anecdotal reports that fasting does not induce the same benefits as the tumor growth accelerates once the fast is over.
Hypothetically one could fast long enough to kill the cancer cells however we don't know how long it would take ; 10,30,60 days?
If I was facing cancer I'd personally go on a fast from the moment I get diagnosed under a doctor's watch unless it's one of the cancers that feed almost exclusively on glucose; I'd simply switch to a fully ketogenic diet.
It's true that a 60 day keto diet is much easier to implement than a 60 day water fast. Anyhow I think this is an interesting area of research; the treatment of cancer as a metabolism related disease.
My take home message is that one should limit his consumption of carbs to the bare necessities (green veggies, nuts and the beneficial fruits) and in case one is fighting cancer in the hypothesis were an extened fast is impossible one should go on a ketogenic diet with as low protein as possible without inducing muscle wastage.
Sorry for my tangential questions. I am indeed interested in a prostate cancer treatment via ketosis. My relative has prostate cancer and I am also trying to figure out whether it's better to suggest he eat more to support his immune system or to induce ketotic metabolism. He's taking hormonal ejections of some kind.
Are you saying that a ketogenic diet is more effective than fasting outright for someone who has already been diagnosed with prostate cancer?
A fast will be superior to a ketogenic diet for all types of cancer there's no doubt in my mind that if one were to fast long enough and kill all the cancer cells you'd be ''cured''. However this is impractical for many reasons; the health of a cancer patient, the unknown duration of the fast (does it take 30,60,90 days? more? we simply don't know the studies haven't been done)...
A keto diet works very well for some cancers (checkout the first page of this thread where this is discussed further) and is implementable on the long term; a person diagnosed with a brain tumor could fast for a week prior to chemo/radiation and implement a ketogenic diet for the rest of his life en théorie, idem for someone who's been diagnosed with prostate cancer.