Hi Robin, 
My response, I'm sure, will be one of many. The reason that you could gain
so much weight back so quickly is that you cranked up your insulin
production, especially through the night, which leads to salt retention,
which requires water to keep the salt in suspension. Retained water can
rapidly increase weight. 

There are several different paleo options for weigth loss. On one extreme,
as outlined by Dr. Ezrin, in his book 'Your Fat Can Make You Thin', you can
just eat enough protein to meet your needs, along with some supplements, and
that will get you into ketosis and burning your own body fat for energy.
There is about a 3 day shift into ketosis but after that, it is quite easy
to follow. 

A more common approach is to eat a diet with few carbs, dominated by fats
(60% to 70% by calories) and moderate protein 20% to 30%. 

With either of the above ketogenic diets, you should monitor your potassium
and take potassium supplements if it goes down at all, as that will reduce
your risk of developing kidney stones. You should also  use Ketostix and a
blood glucose monitor and test yourself each morning to ensure that you do
not develop ketoacidosis.  

There is also a paleo paradigm, championed by Ray Audette, the author of
'Neanderthin', whereby you eat only foods that could have been harvested or
killed with the aid of a sharp stick. This includes meats, vegetables, and
berries/fruits year-round. However, since paleo humans were unlikely to get
access to berries and fruits all year, you may be better off eating only
vegetables and meat. 

Professor Loren Cordain, author of 'Paleo Diet' and other books, advocates
fat intake below 30% and his ideas are often offered by posters here. He was
certainly a major factor in getting the word out about Paleo dieting. 

Most of us here at Paleofood advocate free range meats and organic
vegetables. I believe there is a consensus that two of the most
important/harmful neolithic foods that should be avoided are sugar and
grains.  There are almost as many nuances to each of these dietary paradigms
as there are list members so I'm sure I won't have the last word on this
topic. Nonetheless, I think that is a fair overview of the Paleo perspective
on weight loss dieting. 
 
I hope that helps. 
Best Wishes, 
Ron Hoggan