Why Reheated Pizza May Be Less Fattening

Leftover pizza and pasta may be better for your waistline than the fresh version. (rob_rob2001)
Leftover pizza and pasta may be better for your waistline than the fresh version. (rob_rob2001)

Do you like leftover pizza or pasta for breakfast? If so, science may offer a reason to indulge.

Starchy foods like pasta, pizza, bread, and potatoes can spike your blood sugar and are easy for your body to convert to fat. These comfort foods can cause problems for diabetics and are typically limited if you’re dieting to lose weight. Yet, you may be able to use food chemistry to change how your body digests these foods simply by refrigerating them.

How Starch Works

A starch is a polysaccharide (type of carbohydrate) used for energy storage in plants. When you eat starch, digestive enzymes readily break it into simple sugars, which raise your blood sugar (glucose) and may be converted into fat to supply your body with energy. Your body releases a flood of insulin to bring the level of glucose in your blood back to normal. The swift rise and fall of blood sugar can lead you to feel hungry, even though you just ate, and can lead to health problems. So, many dietitians recommend choosing foods rich in fiber, which is an insoluble carbohydrate that does not cause a rapid change in blood sugar levels.

Regular Starch Versus Resistant Starch

How does this relate to your breakfast of cold or reheated leftover pizza? Assuming you refrigerated the pizza (as opposed to leaving it out on the counter overnight), the temperature change may change the starch into what is called resistant starch. Its called resistant because it resists the enzymes that would break it into simple sugars. Resistant starch behaves more like fiber, which means it wont have the dramatic effect on blood sugar, plus you may absorb fewer calories from the food.

Research into Resistant Starches

Initial findings on resistant starches were reported by Dr. Denise Robertson, senior nutrition scientist at the University of Surrey, UK. Her research indicated that cooking and cooling pasta caused it to be digested more like fiber. Dr. Chris van Tulleken tested the idea on the BBC television show, Trust Me, I’m a Doctor (October, 2014). In Dr. van Tulleken’s study, blood samples were taken every 15 minutes for 2 hours after volunteers ate freshly cooked and reheated pasta. Blood sugar increased 50% less after eating the reheated pasta than after ingesting the fresh pasta. Its unclear exactly what type of chemical or physical change occurs as starch is cooled, leading it to resist digestive enzymes. Dr. Robertson is continuing her research into starch metabolism, funded by Diabetes UK.

The Bottom Line

Does this make leftover spaghetti or pizza diet foods? Not exactly. A simple marinara sauce on your pasta won’t contribute too many calories, but fat and protein from meatballs, sausage, or cheese are another matter. The same goes for pizza. The starchy crust is only part of the equation. You may be able to cut calories there, but the cheese and toppings will still affect your weigh-in results. However, if you are insulin resistant, chilling starchy food before eating it may be just what you need to enjoy your meal without making yourself sick.