A first study involving people suggests that reducing calories could actually help slow down biological aging. The said study saw those who cut their daily caloric intake by 25 percent experienced the aging slow down by as much as 2 to 3 percent.
So, can restricting calories really do this and help healthy adults extend life? Well, it seems as it it could be a possibility.
The landmark study, published on February 9 in the journal Nature Aging, saw a two-year intervention that required those involved to reduce 25 percent of their daily calories. They saw that the pace of their body’s aging process slowed down indeed. This means that there also was a 10 to 15 percent reduction in mortality risk. The researchers said that this was equal to quitting smoking.
“Our findings are important because they provide evidence from a randomized trial that slowing human aging may be possible,” said Calen Ryan, PhD. He is a research scientist at Columbia University’s Butler Aging Center in New York City. He is also co-lead author of the study.
While many find this kind of caloric restriction challenging, the study stands behind the concept that behavioral changes (especially one without drugs), can have a significant impact on aging, Dr. Ryan added.
“This paves the way for future studies of other interventions, such as time-restricted eating or intermittent fasting, which might be more scalable and achievable in a broader sector of the population,” added Ryan.
Benefits of Calorie Restriction on Metabolism and Heart Health
The study made is part of an ongoing study called CALERIE (Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy). This started in 2006.
Previous studies that made use of CALERIE trial data have also demonstrated the multiple benefits from cutting calories. One found that calorie restriction was able to slow down aging-related changes in physiology connected to the liver, kidneys, metabolism, blood vessels, as well as the immune system. Another one showed that there was a reduction of risk factors for heart disease and type 2 diabetes. It also showed that there was improved cardiovascular and metabolic health for individuals involved.
The new study was made to see if these previous findings were right. “We wanted to find out if signs of slowed aging at the organ-system level were also apparent at the cellular level,” said Daniel Belsky, PhD. He is an associate professor of epidemiology at Columbia Mailman School of Public Health and a scientist at the Butler Aging Center in New York City.
Measuring Biological Age
Decades of research have been collected but these made use of animal models. Findings showed that caloric restriction (not malnutrition) improved the life and health span. They wanted to know if the same applied to humans.
“Given how long humans live, it’s not feasible to do a rigorous clinical trial to answer this question,” said Daniel Parker, MD, study coauthor. He is a geriatrician and an assistant professor of medicine and neurology at Duke Health in Durham, North Carolina.
So, researchers put all their efforts to determine how to measure a person’s “biological age,” instead of chronological age, to find signs of slowed aging, said Dr. Parker. One good way to do this, according to him, is to analyze the epigenome.
“While our genetic code remains largely unchanged over the course of our lives, our cells are constantly making reversible modifications to our DNA that turn genes on and off. These reversible modifications to our DNA are referred to as the epigenome,” he explained. Researchers then compare the epigenetic changes to a reference population from a previous study to estimate biological age, added Parker.
Participants Closely Monitored for Vital Nutrients
In the latest CALERIE study, they randomly assigned 220 participants to the calorie restriction group or a control group with no restrictions. The former had 143 people (44 men and 99 women), while the latter had 75 people (22 men and 53 women). As for the population, 76 percent were white, 15 percent were African American, and 9 percent were Asian, Native American, or Pacific Islander. The average age was 38. As for the average baseline body mass index (BMI), it was 25.1. This meant that many of them were normal and overweight, as per the National Heart, Lung, and Blood Institute.
Scientists made use of complicated methods to estimate the number of calories each needed to maintain weight. Then, they took note of the baseline and set personalized goals that removed 25 percent from the original number.
That target level (25 percent) was chosen because this degree of calorie restriction saw the optimal results to enhance life and health span in animal models. This was also discovered to be the most feasible for those in the original pilot study from 2006, as per the authors.
“It’s important to note that this was a study of moderate caloric restriction without malnutrition,” said Parker. Those considered underweight, depressed, or had a history of diabetes, heart disease, or an eating disorder were not part, he also said.
Those involved in the study were given advice on how cut calories while making sure they get the recommended daily nutrients. They were also provided with options for eating patterns that can help with cultural and individual preferences.
“Participants in this study were closely monitored throughout the study to make sure they were meeting all their macronutrient requirements, and participants’ weight was closely monitored. If anyone lost too much weight, they were instructed to increase their caloric intake,” Parker explained.
The 25 percent calorie reduction and maintaining it was challenging for many. In fact, a lot of them couldn’t quite reach the goal. The average calorie reduction was only 12 percent by the end for many by the time the trial ended. Still, many of them lost an average of 16 pounds in the two years that the study took place.
“Reassuringly, there was no evidence that caloric restrictions negatively affected participants’ sleep, cognitive performance, or quality of life,” said Parker.
Fewer Calories Slowed Down Aging
In order to measure the effects of calorie restriction on biological aging, investigators looked at the blood samples from trial participants at pre-intervention baseline and after 12 and 24 months during the follow-up period.
Researchers saw that restricting calories did slowed the pace of biological aging in the long run. Plus, They noticed a dose-response effect: this was where those who reduced their caloric intake more had a greater decline in the pace, said Parker. “These findings are exciting because they provide evidence that the pace of biological aging isn’t set in stone, but can be affected by interventions like caloric restriction,” he said.
The findings added to what they already knew, said Jamie Justice, PhD. She is a researcher and assistant professor of gerontology and geriatric medicine at Wake Forest School of Medicine in Winston Salem, North Carolina. Dr. Justice, however, was not part of the CALERIE study.
While eating less meant that they lost weight and experience several health benefits, more research is still needed to supplement the study and to see how calorie restriction has an impact on aging, she said. A follow-up of is now happening to see if the intervention had long-term effects on aging the healthy way.
Why Fewer Calories Would Slow Down Aging
To put it simply, calorie restriction has an impact on nutrient-sensing pathways and energy metabolism in such a way that it can reverse or reduce the effects of aging, said Dr. Belsky. These said pathways, aptly called “nutrient-sensing,” contain nutrient levels that impact activity.
Part of that effect is because of a process called hormesis, said Justice. “When you give the body or an organism a little bit of a stressor, over time it can activate certain pathways that can actually end up promoting health,” she explained.
Take exercise for instance, Justice said, “You’re stressing the body just a little bit and by doing that, some of these key pathways have to change how they function and signal. In a similar fashion, restricting calories also gives your body a little bit of stress at the cellular level and creates changes in pathways that are associated with lifespan, including those that involve human growth hormone and insulin.”
Intermittent Fasting or Time-Restricted Eating May Bring About the Same Set of Benefits
If caloric restriction is too difficult, there is also growing evidence that shows how other methods may “trick” the body and achieve similar benefits, said Justice.
Although the data is still differing when it comes to intermittent fasting when it comes to the effectiveness in reducing calorie intake, Justice said, “Time restricted eating seems to have really profound effects, especially in people who are in their forties and fifties, who want to either lose a little weight or who are at a healthy weight and just looking to improve their biology.”
Caloric Restriction for Long Periods of Time
Before doing any form of calorie-restrictive diet, always talk to your doctor, advised Justice. “It needs to be done under the care and guidance of a professional because it’s not without risks,” she said.
As long as you are getting the recommended amount of nutrients, restricting calories is thought to be generally safe. Unless, of course, if you are considered underweight or you can become underweight because of the caloric restriction, said Julia Zumpano, RD, with Cleveland Clinic’s Center for Human Nutrition.
It is always better to first meet with a registered dietitian so that they can create a plan for you and make sure you are getting all the nutrients you need, she said.
“I would advise restricting calories from foods and beverages that provide empty calories (very little to no nutrients). Examples include soda, sweetened coffee drinks, punch, lemonade, candy, pastries and cookies, fast foods, chips, sour cream, creamy salad dressings, and cream cheese,” said Zumpano.