Brain works just with ketones.

 A how am shared, by brain assimilating a needing in glucose its  an   conditional  needing , based on fuels sources, getting from food. Diets, suppressing  a manufacturing   ketones , as any diets ,where are more 30 perc. of energy entering from population are proteins and carbohydrates , are force brain assume on glucose as for fuel.

Researches are shown, that in a few peoples used a right ketogenne diet with 10-12 carbohydrates  less are ability using for satisfaction till 70 perc. of energy  needing for brain. Other energy needing of brain satiating  for gluconeogenesis calculation.

 Thus, our brain can to satisfaction an own and all needing energy  with liver, using an early stocked glucose, process gluconeogenesis or ketones, not depending on that you are eating carbohydrates or not. And when our organism adapting to a very low carbohydrate diet or not carbohydrate, brain uses a big part for energy from ketones, and liver manufactures a right glucose a what a need, that covering remaining part. A level of glucose in blood staying stable , and brain getting all needed fuel, and if you are eating carbohydrates. This  is a big meaning by evolution vision pint.And , hunters-collectors are often without meal stayed within a few hours or days, using that getting meal.Ability  using a combination of ketones and glucose for brain feeding probably has been a key to surviving. And on the full starving or ketogennne as without carbohydrate diet are glycogen sources giving 100-200 gr of glucose /day from a best balanced ketogenic diet its will understand,why  a    dietic  ketosis or limiting carbohydrates is good enduring in different hard situations and conditions.

 A not carbohydrate diet is eating food with 100 gr of carbohydrates, are fish, meat, clean animal and vegetable fats.For example, a carnivorous diet is diet meat-eating or diet by carnivorous, when human nothing eating, just eating meat and fats is carbohydrate free. Ketogenic diet or keto-diet is a not avoiding on 100 perc are carbohydrates, thus manufacturing ketones starting , when quantities of carbohydrates using for a day, are less  on 20-50 gr, and its to varies  from a human to human.