In my case, it turns out that my grandfather, who died when I was much younger, had diabetes, as did an uncle (also deceased). Understand what actually constitutes a healthy diet and lifestyle. It turns out that a serving of oatmeal is only one cup cooked, or about half my typical bowlful. We tend to "walk it off" and "play through the pain" rather then actually dealing with it in a constructive fashion.
Despite not eating sweets (other than the ice cream), I had way too much sugar in my diet. Even "whole grain" foods are quickly converted into sugar by the body. But, like me, they have large gaps in their understanding (and perhaps an even larger gaps in what they are actually doing)