The Feb 22 and 29th issue of Time magazine has several articles on longevity. One entitled "It's the Little Things" dances around the concept of fasting and ketogenic diets. Valter Longo of the USC Longevity Institute studied fasting. But there was no mention of ketosis. It now seems clear that the main reason fasting can prevent cancer is that cancer cells cannot metabolize ketones. A fasting diet puts a person into ketosis, and there is not enough blood sugar for cancer cells to survive. Cancer starves to death in ketosis. If there are large tumors it's probably too late for ketosis to help. If there are small tumors ketosis may be an effective weapon. If there are not yet tumors then ketosis may prevent cancer.
Why are scientists and doctors ignoring the ketogenic diet as a weapon against cancer? Here is a study of the use of ketosis for advanced cancer patients. But it's not clear if they proved the patients were in ketosis with blood testing. Trusting people to be honest about their diet is not scientific.