hi Deb,
I confess that I don't have SPII yet, so perhaps Dr. S. has addressed this elsewhere in her book. Just wanted to point out that yes, certain cells in the body lack mitochondria, which are necessary in order to use ketones in the Krebs (citric acid) cycle for energy. These cells require glucose instead.
I notice she uses the starvation model as her example
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The only time that your brain, red blood and kidney cells use fats for energy is when you have not eaten in over seventy-two hours. At that point these cells can switch to using ketones (a breakdown product of fats) for energy.
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In the case of a ketogenic diet, eg Atkins, or that used to treat epilepsy in young children, the person is consuming adequate protein in addition to the fat, and generally a minimal amount of carbohydrate too .. eg 20 grams. But even in the absence of any carbs from the diet, the liver will produce necessary glucose from proteins .. this is called
gluconeogenesis. If the person is starving, then the liver will break down proteins from the body itself .. starting with recycled dead cells, etc, then muscle tissue. If adequate protein is consumed in the diet, then that is what will be used instead. So, even in the case of starvation, the body is never running 100% on ketones; there will always be a nominal amount of glucose being produced to supply those cells that need it.
It's a very long article, but if anyone has the time and is interested, this whole process is explained very well in Chuck Forsberg's
Adiposity 101.
Doreen