And, even fruits and vegetables are limited because they, too, contain carbs.
And it may be this particular evolutionary adaptation which perhaps emerged to keep said noggin fed when food was scarce that also enables the brain benefiting effects of the ketogenic diet.
Two other things to keep in mind are fasting, and your training plan during the first month.
I bought these Ketone Testing Strips and they seem to be getting the job done for testing the level of ketones my body is producing.