I am dieting, and control my blood glucose through the use of food (instead of medication that I used to have to use).
I have lost 81 pounds and am working on the last nineteen.
Generally speaking, I eat mixed greens (never wasting my calories or food intake on iceberg lettuce) sliced onion, tomato, avocado, some hard cheeses grated in various combinations for a salad.
For protein I eat lean meat (breast of chicken, no skin) some veal, pork loin, beef tenderloin, some fin fish (tuna, snapper, etc. I'm not a huge fan of fin fish) shrimp, clams, mussels, oysters... that sort of thing.
Vegetables are green beans, asparagus, some squashes, etc. Steamed usually.
Grill, or bake/roast instead of frying or sauteeing. Steam the vegetables instead of boiling, or sauteeing (we roast them sometimes too, like asparagus).
Keep it simple, lean, green and use herbs and garlic with some salt and pepper to their best advantages.
If you need a touch of fat, add olive oil (I don't like canola, but you can use that too if you choose) and I do mean a touch. If you need butter, use whipped. I know you'll hear all about those "good for you" spreads like Smart Balance and the like, but there is no way that gunk is going in my mouth.

If it doesn't melt... ick.
That's essentially it. Oh, and snacks are judicious amounts of some nuts, walnuts, pistachios, etc. Cashews tend to spike my blood glucose so I go sparingly with those.
Oh, and I drink water. Lots of water. Black coffee in the am.
Hope that helps a bit.