Oatmeal is a great source of whole grain and fiber. Fiber is good for lowering cholesterol, but based on the difference in Glycemic index, it can affect your blood sugar quite differently. Steel-cut oats are the least processed, offering a slow energy release with a low glycemic index, best for people with diabetes. Since it might be a little harder in texture, it needs to be cooked with extra water and for a longer period of time. Cooking in a slow cooker or an instant pot would be easiest. Rolled oats, steamed and flattened, cook faster but have a slightly higher glycemic index. They offer similar nutrition to steel-cut oats. Instant oats are the most processed and cook the fastest but have the highest glycemic index. Even though it seems like a healthy food, but it can spike your blood sugar.