Marcia asked about...
> you may notice a lack of energy at first...

Someone else here will have to tell you the "orthodox" answer to this;
but, I'll tell you what I experienced. ...   Although I felt immediately
better, I found that the transition IS work for the body at the very
first (couple of weeks?)-- adjusting to new typical intake and
eliminating products and by-products of the old way of eating.
Particularly, I had a much harder time staying hydrated through the
transition, because my system was all of a sudden MUCH more efficient at
eliminating water (no more swollen ankles!).  I had to work at making
sure I got enough of both electrolytes and water.   I read somewhere that
dehydration is the most common cause of fatigue (other than overwork!).

What I did (probably not pure paleo but it works for me) is to make up
two liter batches of  my own "oral rehydration formula"  which is kind of
a light lemonade:  2 liters water, 1/2 tsp salt,  juice of 1 lemon, bit
(very little) of honey or maple syrup, shake well.  I try to get a batch
a day down.  I try to do this again whenever energy lags.  It makes a big
difference.   After I heard that Tibetans and Nepalese put both salt and
ghee (clarified butter) in their tea, I tried another trick.  Sometimes
when my energy flags I'll throw a little dash of salt in a big mug or two
of weak tea.

Of course, if your intake is less than what you need, you will also run
out of energy, obviously.