Beans & lentils have about 5-10g of resistant starch per cup cooked, depending on the kind.
So check out this excellent 3.5-minute video by Dr Michael Greger that doesn't mention resistant starch, but that's what it is he's talking about. Watch how beans not only blunt a BG spike as part of a meal side-by-side with a high-GI carb meal, but persists to blunt BG spikes in subsequent meals or even sugar water, even into the next day.
Incidentally, I have confirmation from some N=1s out there that a ketogenic dieter can remain in ketosis and have zero BG spike consuming up to 30 grams of resistant starch (Bob's Red Mill Potato Starch) per day either along with a Z/VLC meal, or all by itself stirred in water. Accordingly, LCers are just plain ignorant and wrong about Resistant STARCH! (deploy garlic necklaces and crucifixes).
I should be posting on that and other N=1 stuff soon.