I didn't gain weight until after fibro and I found it hard to exercise. I also have multiple other health problems. I have two friends with fibro, both healthy in other respects. One is skinny as a rail, and the other is overweight.
I think many people with fibro tend to be overweight because A)It is difficult to exercise due to the fibro itself, B) Many fibro medications cause weight gain, and/or C) Other illnesses tend to run concurrently with fibro, and they often make it more difficult to exercise.
Just my opinion, but I think if an unhealthy lifestyle was the catalyst to everyone's fibro, then more Americans would be afflicted. I know plenty of people whom I would consider to have a much unhealthier lifestyle than I, and they don't have fibro (that I know of). It is so frustrating to have a chronic health condition with no definitive cause or cure.
Not to hijack, but what I find interesting is the number of people who have had spinal problems prior to a fibro diagnosis. I was diagnosed after my second back surgery, and I've always wondered if there is a connection. I also wonder if having another chronic pain condition (back, arthritis, migraines, etc.) screws up the pain processing centers in the brain.