The benefit of cutting calories has typically been associated with weight loss. But does calorie restriction prolong life, as well?

The answer just might be yes, according to new research. Reducing calorie intake by 15% for two years has the potential to slow the metabolic process that leads to aging, the study found. It can also protect against age-related diseases.

Even just one year of a reduced-calorie diet had its benefits in terms of a reduced metabolic rate. As the rate continued to drop into the second year, participants experienced an overall decrease in oxidative stress, which has been linked with diabetes, cancer, Alzheimer’s disease and more.

“Reducing calorie intake provides health benefits to all people regardless of their current health status, said Leanne M. Redman. She is lead author of the study and an associate professor at Pennington Biomedical Research Center at Louisiana State University.

Previously, studies with animals suggested that restricting calories by as much as 25% can extend life. The new study led by Redman, her colleagues and the National Institute on Aging sought to find out whether the same was true in humans.

How it worked

The research started off with small-scale pilot experiments to address different variables. One example was what kind of calories restriction could participants stuck to, in terms of only diet, only exercise or both. Another focused on what level of restriction would influence aging biomarkers, or biological measurements that differentiate those who live longer from those who live the average life expectancy.

From there, three universities – Pennington in Baton Rouge, Washington University in St. Louis and Tufts University in Boston – conducted alrger studies. Redman and her team at Pennington reduced participants’ calories by 25% through diet alone. Reduction in calories for each participant was estimated based on weight loss rather than calculating daily calories.

With this method, participants achieved 15% actual calorie restriction over the two years. As a result, the participants lost an average of 20 pounds by the end of the first year, and maintained this weight loss in the second year. This, in turn, meant metabolic rates slowed, at which point the body becomes more efficient in using fuel to produce energy.

“It’s important because every time we generate energy in the body, we generate byproducts,” Redman said. Byproducts that stem from normal metabolism accumulate in the body and damage cells and organs over time. And this damage is what leads to a shorter lifespan.

What it means

So is it true – does calorie restriction prolong life?

There’s certainly a correlation between limiting calories and living longer, as the research notes. But exactly how calories restriction prevents aging requires further research.

In the future, Redman would like to reassess the participants of this study to determine whether they’ve maintained their weight loss. She would also like to observe long-term results of restricted calorie intake.

In the end, cutting calories isn’t the only factor in longevity.

“What’s important is they’re living longer and free of disease,” Redman said.