Diabetes Nutrition: General Principles
Why There's No "One Diabetes Diet"
Leading sources (including the American Diabetes Association, as cited by Wikipedia) state that there is no consensus that any single type of diet is superior to others for managing diabetes. For people who are overweight or have obesity, the factor most often cited as having the biggest impact on glucose control and insulin needs is reducing body fat mass — even more so than the specific choice of diet.
Carb Counting
This is a method used by some people who depend on insulin: eating a relatively consistent amount of carbohydrates at each meal is described as a way to make glucose control easier. That said, the ADA does not set a single universally recommended carbohydrate amount for everyone with diabetes — the approach is individualized.
Glycemic Index
The glycemic index (GI) ranks carbohydrate-containing foods by their effect on blood glucose levels. Meta-analyses cited by Wikipedia link low-GI diets to better glucose control and fewer episodes of hypoglycemia, though the ADA doesn't make a firm recommendation on GI, citing "mixed clinical benefit" — meaning the evidence exists but isn't considered strong enough for a universal rule.
Among the carbohydrate foods sources describe as preferable: vegetables, legumes, fruit, dairy, and whole grains; fiber, especially soluble fiber, is generally described as a desirable part of the diet. Heavily refined foods and sugary drinks, on the other hand, are described as categories to avoid.
The Plate Method
The Mayo Clinic describes three alternative approaches used by people with diabetes, without favoring any one of them: carb counting, the glycemic-index method, and the so-called "plate method" — a visual guide in which half the plate is filled with non-starchy vegetables, a quarter with protein, a quarter with whole grains or starchy vegetables, a small portion with "healthy" fats, plus a piece of fruit or a dairy serving and water or an unsweetened drink.