Regular rolled oats are, on the whole, far healthier for you than quick oats. The difference lies in their different glycemic indices.
Steel-cut oats and regular rolled oats are each relatively low on the glycemic index compared to quick or instant oats, which have a much higher spot on the glycemic index.
This means that eating quick oats can lead to a bigger spike in your body’s blood sugar level compared to when eating rolled oats. And while this is bad news for diabetics in particular, it’s not such good news for everyone else either.