This deserves mention. An industry-funded study that doesn't entirely find what the industry would like. Whole grain oat flakes reduce blood glucose and insulin responses, but thin or instant oats do not. Funded by PepsiCo, owner of Quaker Oats.

https://www.foodpolitics.com/2021/02/industry-funded-study-of-the-week-a-rare-exception-to-the-rule/