The long-awaited fountain of youth may lie in your calorie count, new research suggests. Part of the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy—also known as CALERIE, the largest human clinical trial to ever look at the aging effects of calorie restriction—the study set out to discover whether the same lifespan-extending effects of calorie restrictions scientists have seen in rodents were the same in humans. The results, published Thursday in Cell Metabolism, showed that limiting calories by 15 percent for two years can slow the metabolic process that leads to aging, oxidative stress and its related diseases (think diabetes, cancer, Alzheimer’s, etc.).
Recruiting young adults to cut their daily calories by 25 percent for two years—the National Institutes of Health-funded study included sites in Baton Rouge, St. Louis and Boston—along with weekly blood tests, bone scans and ingesting a pill that measures internal body temperatures, the participants were monitored from top to bottom. (One group even spent 24 sedentary hours inside a sealed room to record their breathing.) The outcome, however, was worth it: A significant shift in metabolic rates were seen after one year, and the rate continued into the second year, leading to an overall decrease in oxygen radicals.
“Every time we generate energy in the body, we generate byproducts,” Leanne M. Redman, lead author of the study, said of the significance of the results. “These byproducts of normal metabolism, also called oxygen radicals, accumulate in the body and over time cause damage to cells and organs,” she adds. This damage is what has been linked to a shortened lifespan. “Calorie restriction mimicked some of the healthy aging signposts seen in long-lived individuals.”
Biologist John R. Speakman, who did not participate in the research but served on the data safety and monitoring board for the CALERIE project, explained that it’s been well-known since the 1930s that calorie restriction reduces the rate of aging and extends lifespan in rodents, which is exactly why he says the study’s “big contribution” is putting forward the same results in humans that were previously only observed in calorie-restricted rodents: lowered metabolic rates and a reduced production of oxygen radicals.
Exactly how calorie restriction prevents aging, Speakman says is the million-dollar question. While the research supports two theories—”rate of living” or a lower metabolism, and reduced oxidative damage—Speakman stresses that the study only shows a correlation. “We can’t infer that these changes are causally linked to reduced aging,” he says. “Nevertheless, it is a step forward to indicate that these two ideas are not rejected by the current research.”