What Happens to Your Blood Sugar When You Eat Leftover Pizza Instead of Fresh

Recently, the internet has become fascinated with the idea of resistant starch, a type of starch that’s less likely to cause big blood sugar spikes when digested. You can find videos of people saying you should cool down rice, croissants, and even pizza before eating it for more resistant starch. Turns out there are better ways to reduce blood sugar spikes.

How Resistant Starch Affects Blood Sugar Spikes

When we eat starch-heavy foods like pizza, our blood sugar begins to rise as our body breaks down those carbohydrates. When this happens, our pancreas releases insulin, which tells the body to either use or store those carbohydrates.

However, because resistant starch isn’t digested until it reaches the small intestine, it doesn’t cause as significant of an impact on your blood sugar levels.

“Resistant starch is digested more slowly than regular starch, so it can modestly blunt post-meal blood sugar spikes and improve insulin response over time,” said Lauri Wright, PhD, RDN, LD/N, FADA, director of Nutrition Programs and associate professor at USF College of Public Health, told Verywell.

In one analysis from 2023, researchers looked at the relationship between resistant starch, blood sugar, and insulin response in people with prediabetes or type 2 diabetes. They found that certain types of resistant starch were associated with improved blood sugar levels and insulin response after eating.

Why Cold Pizza May Have Resistant Starch

Everything from storage duration to serving temperature can alter the resistant starch levels in food, Meghan Windham, MPH, RD, LD, clinical assistant professor at Texas A&M University, told Verywell.

“There are four main categories of resistant starches: RS1, RS2, RS3 and RS4,” Windham explained. “In particular, RS3 is a resistant starch category containing foods that have undergone retrogradation.”

Retrogradation is a process in which starch is cooked and then cooled back down again—resulting in an increase in resistant starch type 3.

Several studies have explored the impact of this type of starch in foods such as rice, but so far, there isn’t much research on how this process might affect a slice of pizza.

“Leftover pizza may contain slightly more resistant starch because cooling cooked starches can convert a small portion into resistant starch,” Wright said.

“However, the increase is relatively modest and unlikely to meaningfully change blood sugar response for most people,” she added.

Should You Opt for Cold Pizza for Better Blood Sugar?

Factors like protein content and portion size have a more significant effect on your blood sugar than resistant starch.

“Leftover pizza is not a ‘blood-sugar-friendly hack,’ but enjoying it with balance still counts,” said Wright.

At the end of the day, if you’re looking to manage your blood sugar more effectively, look to something other than just cold pizza.

“There are additional ways to keep your blood sugar in control such as consuming meals with both whole grains and lean proteins, incorporating regular exercise, and appropriate timing of meals,” Windham said.