If you do a pubmed search, you shouldn’t have trouble finding scientific studies on diet an insulin resistance. In general, a low-carb diet increases insulin resistance. A high-calorie diet will also increase insulin resistance because of increase fat stores. On the other hand, a hypocaloric (low-calorie) diet increases insulin sensitivity, and so does exercise, especially cardiovascular exercise, which rapidly uses up glycogen stores.
I believe starch can be good for insulin sensitivity as long as one isn’t eating so much as to gain fat.