Your diet will depend upon your physique, i.e. overweight etc., and other health factors. I've been a Type 2 diabetic for 35 years (early onset due to family history). Exercise as much as you can, get down to as close to your ideal weight as possible. I was about 25 lbs overweight and only normally active when I was diagnosed. I had a great wife who helped motivate me to do more.
I can't stress this enough, exercise seriously. Within 2 years I was jogging 5 miles DAILY just around the neighborhood mostly. I'm not much of a swimmer but that is better as it exercises more of your body. My wife would do 100 + laps a day. We both hit the gym 3-4 times a week. By the time I was 50 I was in the best shape of my life, and I was a serious backpacker in my younger days.
You will be surprised how much of a habit it becomes and how if you miss a day in your routine you actually miss it and want to do it. The best advice I can give you is to take it seriously. It's a life long commitment and it isn't as bad as you might think. I'm a senior now but look 15-20 yrs younger than I am and I'm telling you it has actually changed my life for the better.
Life is full of challenges, and if you face this one and take it seriously, you will find side benefits you never really thought of before. I have life long friends who just let themselves hit walls in their life and their downfall has been tragic. They are surviving, nothing more. 90% of it is in your head man, you can either beat it or let it beat you. The fact you are asking here is a good thing.
If you don't have an exercising partner my suggestion is to find one. It makes it more fun and easier to stay with it.