Restrict calories to live longer, study says

People of normal weight may be able to extend their life span by restricting calories, according to a new study that attempted to measure the pace of aging in people asked to cut their calorie intake by 25% over two years.

“We’ve known for nearly 100 years that calorie restriction can extend healthy life span in a variety of laboratory animals,” said senior author Daniel Belsky, an associate professor of epidemiology at Columbia University Mailman School of Public Health.

“It does this by changing biology in ways consistent with a slowing of the process of aging, although the specific mechanisms of how this occurs are still under investigation,” said Belsky, who studies longevity. “We decided to drill down to the cellular level in people to see if the same is true.”

The study used what are commonly known as “biological clocks” to determine the pace of aging in its participants. Bioclocks are designed to measure how old people are biologically compared with their real ages chronologically.

“Our study found evidence that calorie restriction slowed the pace of aging in humans,” said colead author Calen Ryan, an associate research scientist at the Robert N. Butler Columbia Aging Center at Columbia.

“Our findings are important because they provide evidence from a randomized trial that slowing human aging may be possible,” Ryan said in a statement.

But longevity scientist Dr. Peter Attia dismissed the study results as “noise.”

“I just don’t see any evidence that any of the biologic clocks have meaning,” Attia, who was not involved in the study, said via email. He hosts “The Drive,” a podcast dedicated to explaining and applying longevity research to everyday life.

“The only validation that matters — which to my knowledge has not been done, but hopefully will be — is to see if ‘biologic age’ can predict future life better than chronological age,” he said.

Biological age predictors are controversial, said calorie restriction researcher Pankaj Kapahi, a professor at the Buck Institute for Research on Aging in Novato, California.

“At best, they’re telling you something about a very small aspect of aging,” said Kapahi, who was not involved in the study. “For example, grip strength is also a biological age predictor, how active you are is a predictor, and we all know people who fall apart physically but are cognitively all there, so you also need to test cognitive aging.

“Some researchers are trying to boil it down with bio-aging tests,” he added. “This is a much more complex problem, and I think it’s an overstatement to say the tests really predict biological age.”

The CALERIE study

Decades of research in animals have shown that calorie restriction produces health benefits, even slowing the pace of aging. Would the same be true in people?

A study in the 1950s asked people to reduce 50% of their calories, leading to malnutrition or a lack of key micronutrients in participants. Later research often focused on calorie reduction in people whose body mass index would be considered medically obese.

The first clinical trial of calorie restriction in people at normal weight (a BMI of about 20 to 25) started in 2007. It was called CALERIE, or the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy.

Because of the malnutrition found in the earlier study that cut calories drastically, CALERIE asked 143 adults between the ages of 21 and 50 to cut 25% of the calories they typically ate for a two-year period. Another group of 75 people maintained their normal diets, serving as a control group.

During the trial, all manner of tests were done at six-month intervals to gather information on weight loss, change in resting metabolic rate, impact on cognitive function and markers of inflammation, cardiovascular health and insulin sensitivity.