By Mandy Taheri

A study that developed biological age clocks to predict a person's age, which may differ from chronological age, showed that a reduced-calorie diet among the trial participants caused a major reduction in biological aging.

Published on Thursday, the study, whose research was funded by Singapore's Ministry of Education, reiterates similar findings from recent years, most of which sourced data from the national Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study.

"Our analysis of CALERIE participants suggests that 2 years of mild caloric restriction significantly reduces biological age," the study said.

Chronological age is a straightforward measure of age—simply put, it's the number of years since a person was born. Unlike biological age, it does not account for health, lifestyle, genetics, epigenetics and environmental factors. Biological age can be determined by biomarkers, epigenetic alterations and physiological factors, among others.

In the scientific community, biological age can provide a more nuanced and accurate reflection of an individual's aging process because biological age does not increase at the same rate for everyone.

"Biological age (BA) is the most important risk factor determining individual risk of morbidity and mortality, with true BA of individuals generally different from chronological age," the study's researchers wrote.

While the calorie restriction CALERIE participants "achieved only relatively moderate CR (12%)," the study said, "this nevertheless resulted in a significant reduction in several known CVD [cardiovascular disease] risk factors, with reduction in BA estimates."

In sum, the study said the "data suggest that CR, under the conditions realized in CALERIE, was able to significantly reduce biological aging."

Daniel Belsky, an associate professor of epidemiology at Columbia University's Mailman School of Public Health, said: "The CALERIE data in this paper confirm our previous findings indicating that the CALERIE intervention slowed the pace of biological aging."

He said that "the observation of this similar result is important because the authors are using different tools developed in different ways to test the hypothesis and getting the same result."

"That builds confidence that CALERIE intervention really did slow biological aging," said Belsky, who has studied the relationship among caloric restriction, epigenetics and aging and published a paper about epigenetic clocks last year in Nature Aging.

Dr. Jan Gruber, an associate professor in the Healthy Longevity Translational Research Program at the National University of Singapore and co-author of the study, said in an email Friday, "These newer clocks are designed to predict future mortality—directly based on biomarkers," adding, "having such clocks provides a new way to test intervention strategies without the need for decade-long studies."

He explained, "the key idea is that we can learn to predict mortality (biological age) from the big, expensive, rare studies and then apply these insights to any number of much shorter, smaller and cheaper intervention trials."

Gruber continued, "Advanced aging clocks are the only way to rapidly answer questions such as which lifestyle interventions, diet changes, drugs, supplements (if any) actually slow aging and extend healthy lifespan."

Earlier this year, a study at Penn State exploring the connection between calories and aging, analyzed data from 175 participants after 24 months of caloric restriction. It found that after one year of this restriction, the participants lost their telomeres more rapidly than those on a standard diet. But after two years once the participants' weight had stabilized, they began to lose their telomeres more slowly, and near the end they had roughly the same-length telomeres as those on a standard diet.

Telomeres, made from DNA sequences and proteins, cap and protect the end of chromosomes. They become slightly shorter every time the DNA is copied to produce new cells, so their length can be a useful indicator of cells' biological age.