Leftover Pizza Is Healthier Than Fresh Thanks to Resistant Starch

Your refrigerator is secretly a forge for fiber. When you cool pizza to below 40 degrees Fahrenheit, something remarkable happens in the crust. The starches in the dough begin forming long chains called resistant starches. These structures resist digestion, which means another word for them is fiber. Even if you reheat the pizza later, these chains stay intact, so your body cannot break them down into sugar—they mostly pass through. This can help reduce blood sugar spikes, making leftover pizza a better choice for people with diabetes or anyone seeking more fiber for gut health. The effect is not limited to pizza. Rice, pasta, potatoes, beans, and lentils all develop resistant starch when cooled. Scientists have studied this phenomenon using electron microscopes to photograph the long starchy fibers forming in cooled rice, and they have conducted human studies where participants ate old rice at 6 A.M. to measure the health effects. Heating then cooling starch changes its properties, much like tempering chocolate or forging stronger steel.