I recently found a great site that is answering some questions for me and part of it explains weight gain. It is:
The doctor here has extensive research into perimenopause (AKA 8-10 years of pure misery for some of us, and can start much younger than at least I thought!). There is tons to read up on at this site and you can discover the weight gain connection to too much estrogen. And, there is hope and treatment options explained extensively!