I lost a lot of weight (especially relative to body percentage) leading up to and following leaving STBXAH. I went from 118 to 98 over about 4 months. I also had/have terrible insomnia. Now that we've been apart, no contact, and almost finally divorced (divorce will be final next month), I am finally starting to sleep better. I have always been an avid exerciser, but in the months after I moved out, I found that I had a hard time doing anything: eating, moving, breathing, just getting off the couch in any capacity. I started getting a little bit worried when I dropped under 100 lbs, and I definitely think I was depressed.
But it gets better! In January, I returned to exercise, and it was sooooo cathartic! I love exercise more than ever, and I find that the endorphins have really helped get me out of my funk. Also, hard exercise requires me to eat more so that I'll have the energy to get through my workouts. My sleep is slowly getting more regular, and I definitely think the exercise has helped with that. Plus, I joined a gym near my house, and the classes that I go to have allowed me to start making some new friends, so it's been good for getting a life.
Finally, I also committed to a new year's resolution of "getting a life." I joined a book club, met a couple of great girlfriends (whom I credit with literally getting me off of my couch), and I am consciously going out and doing all of the things that I love that I forgot about/wasn't allowed to do when I was in the madness of living with STBXAH.
My weight has somewhat stabilized at 102, which is thin, but a bit healthier. The more important thing is that I've finally stopped losing weight, and I feel like I have some control over my body/health now. It's definitely a mind-body connection, and it's nearly impossible to be physically healthy when you are emotionally unhealthy. But the good news is that you can and will heal! I'm not completely there yet, but my optimism is back, and I feel like my real self is also back.