Starchy foods like pasta and potatoes contain a linear type of starch that we digest easily, causing a high glucose load and insulin response after a meal (high GI). When these two foods (rice and lentils too) are cooked then cooled, the starch reconfigures (a process called retrogradation) into a less digestible crystalline form called ‘resistant starch’ (RS) with a lower GI. RS passes through our small intestine, into the large, and feeds our gut bacteria which makes them happy. We absorb fewer glucose molecules at a time and thus have a lower insulin spike. Raw oats and (cooked) cannellini beans also contain a lot of RS. Here is a well researched webpage with deeper detail.
I have included recipes for a yummy potato/pasta/rice/lentil salad, a bean salad HERE and a very quick no-cook Oatmeal-nut-dried fruit-chocolate cookie bite HERE. (these are darn good, if I must say so say myself.)