Our bodies must make adjustments when moving from one major food type to another.  As an example, when eating carbs our cells can use the glucose directly for energy in a simple fermentive process very similar to the way yeast and bacteria use glucose.  However, when eating mostly fat for energy our cells must go through a much more complex process of converting fatty acids into energy and this requires mitochondria in the cells to make the conversion.

In our modern culture most of us have spent our lives eating mostly carbs so our cells only have the minimum number of mitochondria necessary to carry out specialized functions for the cell but not enough to efficiently metabolize fatty acids to provide all the energy the cells need from fat alone.  The cells must create more mitochondria to efficiently use the fat as a primary energy source and this takes time as mitochondria are very much like small living cells within our larger living cells.
 

Hi Lex! Yes, I'm reading here, too <g>.
I was surprised when I read this, for that seems to be the explanation of what dr Atkins called "the golden shot", i.e. that the first time you start LC, it work MUCH better than the second, the third and so on time...

It would explain a LOT to me, like why I don't lose weight quicker now, I simply have too many of those mitochondria left from my previous LC and ZC adventures...!  It doens't matter, I will still stay ZC and mostly pemmican, too, but I like understanding these things. Thanks!!!  (Or have I got hold of the wrong end of the stick here..?)