In Mongolia especially in rural area local people eat only meat/fat from horses, sheep and camels and drink heavy fermented horse milk. They do not eat any frui

In Mongolia especially in rural area local people eat only meat/fat from horses, sheep and camels and drink heavy fermented horse milk. They do not eat any fruits or vegetables (it is hard to grow those in a semi-desert). They also avoid fish even when it is plenty in nearby rivers or lakes. Mongolia is on top of the charts regarding death from liver and other cancers and from heart decease. So I very much doubt that keto-diet has a protection against cancer. On the other hand the life expectancy both absolute and conditional at a particular age of Mongolians either matches or within 2-3 years of that of Indians who eat mostly vegetarian diet. So if Mongolian have high prevalence of cancers, then they must have less prevalences of other deceases. So if keto diet has any protection, then it is against those other deceases, but not for cancer and heart ones.