Online influencers claim the secret to low-calorie rice, pasta and potatoes may be as simple as chilling out.
Are they right? Not quite. But a small yet solid body of science does suggest that chilling these carbohydrate-rich foods after cooking them still could help people slim down.
For several years, wellness and nutrition influencers have promoted a process called retrogradation, urging people to cook, chill, then reheat carbohydrate-rich foods. They say doing so can cut the calories.
Retrogradation is real, but it isn’t quite that simple.
Most of the carbohydrates in these foods — as well as most of the calories — come from starch, of which there are two types: hard-to-digest amylose and easily digested amylopectin. The latter is processed quickly and spikes blood sugar. The former is processed slowly and moderates blood sugar.
Most raw carbohydrates (think uncooked potatoes) are made mostly of the hard-to-digest starch (also called resistant starch), but cooking converts it into the easily digested one. This is why diabetics need to be mindful when eating starchy foods.
Here’s where the influencers get excited. Chilling those cooked foods triggers “retrogradation,” a process that converts easily digested starch back into resistant starch, making it harder to digest even if the food is then reheated.
What does that mean for calories and blood sugar? Here’s what we know:
Studies of how retrogradation influences diet mostly have been small and focused on how consumption of resistant starches influences blood sugar, particularly for diabetics.
Multiple studies since 2015 have found that people who ate rice that was cooked and then cooled had sometimes significantly lower blood glucose levels after eating compared to people who ate freshly cooked rice. Those findings are generally well-accepted.
Less studied is whether retrogradation also reduces the calories available from these foods.
Kind of, says Dr. David Ludwig, an endocrinologist and researcher at Boston Children’s Hospital. “It doesn’t appreciably change the calorie content of that food,” he explained. “(But) it may well affect your hormones and metabolism in a way that makes controlling calories a lot easier.”
Though retrogradation’s effects on calories is neither as direct nor as dramatic as some suggest, it nonetheless has promise as part of healthier eating, Ludwig said.
Eating foods high in resistant starch reduces the surge in blood sugar typically seen after consuming cooked carbohydrates, he explained. And that’s key not only for diabetics.
Studies have shown that those sugar spikes activate the brain’s reward mechanism and trigger cravings, making overeating at snacks and later meals more likely.
Also, those blood sugar surges increase the body’s production of insulin, which not only makes us feel hungry, but prompts the body’s metabolism to store more calories as fat, Ludwig said.
“When the food retrogrades, it digests more slowly,” he said. “It’s going to keep your blood sugar more stable. You’ll have less insulin to drive fat storage and likely have an easier time avoiding overeating.”
If you eat a diet high in refined starches, chilling can technically mitigate some of their negative impacts. But Dr. Walter Willett, professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health, says that to be effective, it would have to be done consistently, and he questions whether that’s practical for most people.
It also isn’t plug-and-play simple. Retrogradation works better with some grain varieties than others. Some food manufacturers favor varieties of rice, for example, that are naturally low in resistant starch because they cook more quickly. But this information rarely is available to the consumer, so it’s hard to know when chilling makes a difference.
Willett also noted that retrogradation only helps with blood-sugar effects.
“Chilling does not restore the losses of fiber, minerals and vitamins that have been removed in the refining process,” he said.
Better, he said, would be to keep it simple: Substitute minimally processed whole grains cooked as one normally would.
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J.M. Hirsch is a food and travel journalist, and the former food editor for The Associated Press.
