Usually, when we report what’s new in the world of medical research discoveries, we have to add the disclaimer that the work was done on animals. While animal studies can teach a lot, they are not the same as human trials. To get to the stage of human testing, methods and medications must first be proven relatively safe. However, the results of animal studies and human trials can be very different sometimes.
A new randomized human trial has found that calorie restriction slowed the speed of biological aging. It is well known that calorie restriction slows aging in animals, but this is the first human study of its kind.
Cutting calories slowed the natural degeneration of DNA by two to three percent. That equals a 10 to 15 percent lower risk of death. That’s the same reduction in risk as quitting smoking. The risk reduction happened when people ate 25 percent fewer calories than they normally did. The study ran for two years.
“In worms, flies and mice, calorie restriction can slow biological processes of aging and extend healthy lifespan,” said senior author Dr. Daniel Belsky, associate professor of epidemiology at Columbia Univ. “Our study aimed to test if calorie restriction also slows biological aging in humans.”
The trial taught researchers which biomarkers to look at while determining how diet impacts age. “Our study found evidence that calorie restriction slowed the pace of aging in humans,” said Dr. Calen Ryan, a research scientist at Columbia Univ. and co-lead author of the study. “But calorie restriction is probably not for everyone. Our findings are important because they provide evidence from a randomized trial that slowing human aging may be possible. They also give us a sense of the kinds of effects we might look for in trials of interventions that could appeal to more people, like intermittent fasting or time-restricted eating.”
Detractors of the diet are quick to point out a flaw: 25 percent is a lot. People in the study maintained a diet eating 25 percent fewer calories than they did before for two years. Dr. Matt Kaeberlein, director of the Healthy Aging and Longevity Research Institute at the Univ. of Washington, said it was “not reasonable for most people” to maintain that diet for a long time.
Indeed, the diet was tightly controlled. Dietitians and nutritionists worked with participants while doctors monitored their health. It was carefully balanced to lower calories while keeping essential vitamins, minerals and other nutrients at healthy levels. It wasn’t simply a case of folks in the study cutting back.
A follow-up study is underway to see if calorie-restrictive diets have a long-term impact on aging. Studies in animals linked cutting calories to a lower chance of heart disease, stroke and dementia. That could hold true in humans.