> Unless you're taking in real carbohydrates from which to derive your
glucose,
> your body has to transform either the glycerol backbone from the fats you
eat
> or protein from either your diet or muscle to make glucose for your
brain --
> thus gluconeogenesis.

Principally, the hormone glucagon  (and to a lesser extent epinephrine and
cortisol) signals the liver to convert its glycogen stores into blood
glucose before fats or body muscle proteins are broken down.  Glycogen
stores can last many hours.

As glycogen stores diminish, gluconeogenesis may be initiated.

> Unfortunately cortisol also promotes fat storage in the
> belly area -- literature is not too clear why, but one guess is that it
makes
> it easier to retrieve during the next stressful time.

But glucagon (enhanced by cortisol) also signals fat stores for conversion
to glucose; a desired effect for anyone wanting to lose weight.

Rob