I'm not an exercise freak, nor am I a dietician, but I was in a similar state when I was finishing my first book. I had packed on 20 pounds I didn't need.
I cut out ALL bread, pasta, as well as starches and sugars that came from anything but raw, natural fruit. Then I started walking four or five miles a day along with weightlifting at home. I lost the 20 pounds in two months.
My brother in law, a physician, confirmed what I guess I already knew: my body learned how to use fat for energy again rather than relying on the carbs, while the exercise increased my overall metabolic rate.
This is some of the best, clear advice I have ever read on SF about weight loss and getting fit.