I did some research and came up with this:

How does the liver convert the food you eat into fuels?
The protein, complex carbohydrates, and fat that you eat -- and the protein, carbohydrate, and fat in your body -- can all be used to fuel your body functions. But first, the liver converts them into chemicals the body's tissues can use as fuel, as follows:

The liver converts the carbohydrates into a simple sugar, glucose, which can fuel most body functions.
It converts any excess protein you eat, over and above what you need to replace the proteins in your body, into glucose as well.
It converts the fats into chemicals called ketone bodies.
Once these conversions are made, the liver exports the glucose and ketone bodies into the blood stream for distribution to the tissues for use as fuel. Found at http://www.nutrition.cornell.edu/nu...st/ketosis.html

Please note that this website does not endorse a low carb diet.
I'm sure I read about it elsewhere (maybe on the ASDL-C newsgroup?) but it escapes me now.
HTH!
Michelle