Because PCOS is a syndrome, there are many different aspects to it. It is most certainly NOT a "disease".
It's an area of research that I concentrated on when I was in the health care field, and one of the things that makes a common thread is the role of insulin resistance. One of the ways to help with insulin resistance, which can actually be quite effective, and that you have control of, is diet and exercise.
Here's a decent article that I just found:
PCOS and DIET by Martha McKittrick
Good luck. Educating yourself is your best tool.