Cutting calorie consumption by 15 percent for two years could slow aging and metabolism and help protect against age-related disease, according to a study with a lead author from the Pennington Biomedical Research Center in Baton Rouge.

The study is one of the first to explore the effects of calorie restriction on humans and is in today's issue of the journal Cell Metabolism.

The study found that calorie restriction decreased systemic oxidative stress, which has been tied to age-related neurological conditions such as Alzheimer’s and Parkinson’s diseases, as well as cancer, diabetes and others.

“Restricting calories can slow your basal metabolism, and if by-products of metabolism accelerate aging processes, calorie restriction sustained over several years may help to decrease risk for chronic disease and prolong life,” said lead author Leanne M. Redman, associate professor of clinical sciences at Pennington.

The second phase of the overall study reports results from 53 healthy, non-obese men and women between ages 21 and 50, who cut calories by 15 percent over two years and underwent additional measurements for metabolism and oxidative stress.

Those in the calorie restriction group lost an average of 19.8 pounds, although they did not follow a particular diet and weight loss was not the study’s goal. No adverse effects, such as anemia, excessive bone loss or menstrual disorders were noted. In fact, both trials led to improvements in mood and health-related quality of life.

“We found that even people who are already healthy and lean may benefit from a calorie restriction regimen,” Redman said.

In lab animals, calorie restriction lowers core body temperature and resting metabolic rate. Redman emphasized that the study looked at the effects of calorie restriction on aging, not weight loss, where discussions of “fast” or “slow” metabolism most often arise.

“We know from mammalian studies that the smaller the mammal, the faster their metabolism and the shorter their longevity,” she said.

Many factors, such as antioxidant mechanisms and dietary and biological factors, influence metabolism, Redman said, but the theory is a slower metabolism is most beneficial for healthy aging and that organisms that burn energy most efficiently should experience the greatest longevity.

The trial supports two of the longest-standing theories of human aging: the slow metabolism "rate of living" theory and the oxidative damage theory, she said.

The second theory ties overproduction of free radicals to oxidative damage to lipids, proteins, and DNA, leading to chronic diseases such as atherosclerosis, cancer, diabetes and rheumatoid arthritis.

While the number of participants was relatively small and the duration short in the context of a human lifespan, biomarkers of aging were improved in study participants. Next steps include establishing biomarkers of human aging and examining the effects of calorie restriction in conjunction with antioxidant foods or substances like resveratrol, which mimic calorie restriction.