Number one cause of diabetes (II) is visceral (belly) fat. Not fat anywhere else but specifically around the belly. Get rid of belly fat and it will greatly improve insulin sensitivity. You will almost never see a type II diabetic with a flat stomach. Second is lack of exercise or a sedentary lifestyle. It’s well studied and documented that exercise promotes insulin sensitivity and lack of it causes insulin resistance . Start working out and /or going for long brisk walks and it will do wonders to your blood glucose. Just taking care of these two will reverse type II diabetes in most otherwise healthy people.
And for those who aren't familiar with the term "visceral", it means fat wrapped around your internal organs. It is possible to have a relatively flat midsection, and still have visceral fat.
As I understand it, fat builds up around your liver over time. Eventually it starts marbling inside the liver, reducing it's ability to perform it's many functions. Then the fat around your pancreas starts marbling inside THAT organ, reducing it's ability to produce insulin.
For those interested in learning more about the how and why of diabetes, and how to reverse it, I'd recommend two books by Dr. Jason Fung, The Obesity Code, and The Diabetes Code. I'd bet a pile of money that you'll learn more from those books than you will by asking questions of your doctor.