Reducing calories may help delay the rate of biological aging, according to a groundbreaking human study.

The groundbreaking study, published on February 9 in the journal Nature Aging,discovered that a two-year intervention requiring participants to reduce 25% of their daily caloric intake slowed aging by 2 to 3%. According to the researchers, this amounts to a 10 to 15% reduction in mortality risk, or around the same degree of risk reduction as giving up smoking. 

According to co-lead author of the study and Calen Ryan, PhD, a research scientist at Columbia University’s Butler Aging Center in New York City, “these findings are significant because they give evidence from a randomized experiment that reducing human aging may be conceivable.”

The study supports the idea that behavioral adjustments — without the use of medicines — can have a quantifiable impact on the rate of aging, according to Dr. Ryan, despite the fact that many people might find this level of caloric restriction to be too challenging. Future research on alternative therapies, such time-restricted eating or intermittent fasting, which may be more scaleable and feasible for a wider segment of the population, will now be possible, according to Ryan.

Calorie Control Is Good for Your Heart and Metabolism

The present experiment, known as CALERIE (Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy), was launched in 2006 and is still underway.

Numerous advantages of calorie restriction have been demonstrated in prior research using CALERIE trial data. According to one study, calorie restriction slows the physiology-related aging changes that affect the liver, kidneys, metabolism, blood vessels, and immune system. Another study found that calorie restriction enhanced cardiovascular and metabolic health and decreased risk factors for heart disease and type 2 diabetes.

The objective of the new study was to investigate those earlier results. As a scientist at the Butler Aging Center in New York City and an associate professor of epidemiology at Columbia Mailman School of Public Health, Daniel Belsky, PhD, explains, “We wanted to see if indicators of slower aging at the organ-system level were also present at the cellular level.”

How Old Are You Biologically?

Animal models have been used in decades of research to show that calorie restriction (without malnutrition) lengthens life and so-called health span. But does this apply to people?

Given the length of human life, a comprehensive clinical trial to address this topic is not practical, according to research coauthor Daniel Parker, MD, a geriatrician and assistant professor of medicine and neurology at the University of California, San Francisco.

According to Dr. Parker, researchers have instead worked hard to figure out how to evaluate a person’s “biological age” rather than their chronological age in order to look for indicators of slower aging. He claims that studying the so-called epigenome is one promising method for determining biological age.

“While our genetic code mostly stays the same throughout our lifetimes, our cells are constantly changing our DNA in reversible ways that turn genes on and off. The term “epigenome” refers to these reversible changes to our DNA, he says.

According to Parker, scientists may determine a person’s biological age by comparing these epigenetic alterations to a reference population from past studies.

Participants in the study were closely watched to ensure they were receiving the required nutrients.

In the most current CALERIE study, 220 participants were randomly assigned to one of two groups: those who restricted their caloric intake and those who did not. There were 75 persons in the control group and 143 people in the calorie restriction group (44 males and 99 women) (22 men and 53 women).

The average age of the 38 people in the study was 76 percent white, 15 percent African American, and 9 percent Asian, Native American, or Pacific Islander. According to the National Heart, Lung, and Blood Institute, the participants’ average baseline body mass index (BMI) was 25.1, putting them in the normal and overweight weight range.

Scientists calculated how many calories each person need to maintain their body weight using advanced procedures. Then, using that baseline, each person was given a goal that reduced that amount by 25%; for example, if their baseline daily calorie intake was 2,000, their aim was to consume 1,500.

According to the scientists, the target level of 25 percent was chosen since it was discovered to be attainable in the majority of people in the initial pilot study from 2006 and had the best benefits in improving life span and health span in animal models.

It’s crucial to keep in mind that this study involved modest calorie restriction without starvation, according to Parker. According to him, participants in the study were not underweight, depressed, or known to have diabetes, heart disease, or an eating disorder.

All participants in the study received recommendations on how to reduce their caloric intake while still getting the essential nutrients, as well as choices for eating habits that would take into account their cultural and personal preferences.

“Throughout the study, participants’ weight and compliance with the study’s macronutrient requirements were thoroughly checked, as well as the individuals’ overall health. Anyone who dropped too much weight was advised to eat more calories, according to Parker.

According to Parker, there was no evidence that calorie restriction had a negative impact on individuals’ sleep, cognitive function, or quality of life.

Ageing was slowed by consuming fewer calories.

Investigators examined blood samples taken from trial participants at pre-intervention baseline and after 12 and 24 months of follow-up to determine the effect of calorie restriction on biological aging.

They discovered that caloric restriction over time decreased the rate of biological aging. Additionally, there appeared to be a dose-response relationship: Parker notes that those who lowered their calorie intake to a larger degree experienced a slower rate of biological aging. These results are fascinating because they show that calorie restriction and other interventions can have an impact on the rate of biological aging, he says.

According to Jamie Justice, PhD, researcher and assistant professor of gerontology and geriatric medicine at Wake Forest School of Medicine in Winston-Salem, North Carolina, these findings expand on what is currently known regarding calorie intake and biological aging. The CALERIE study did not involve Dr. Justice.

She argues that further research is required to support the findings on how calorie restriction directly affects aging because eating less results in weight loss, which can have numerous positive health effects.

The trial’s participants are currently being followed up on to see if the intervention had any long-term benefits on healthy aging.

Why Would Consuming Less Calories Reduce Aging?

According to Dr. Belsky, the current theory holds that caloric restriction alters energy metabolism and nutrient-sensing circuits in ways that prevent or lessen the impacts of aging. Since the activity of these pathways is influenced by nutrient levels, they are known as “nutrient-sensing” pathways.

According to Justice, hormesis is a process that contributes to this effect. Over time, she explains, “when you give the body or an organism a little bit of a stressor, it can really activate specific pathways that can end up encouraging health.”

Justice cites exercise as an illustration. Some of these important pathways must alter how they work and signal as a result of the slight stress you’re putting on the body. Similar to this, reducing calories stresses your body slightly at the cellular level and alters pathways related to lifespan, such as those involving insulin and human growth hormone, says the expert.

The advantages of intermittent fasting or time-restricted eating may be similar.

Take heart if calorie restriction isn’t for you, Justice argues, as there is mounting evidence that other strategies may “fool” the body and produce comparable results.

Time restricted eating appears to have really profound effects, especially in people 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, according to Justice. This is especially true for those who are in their forties and fifties and want to either lose a little weight or who are at a healthy weight and just looking to improve their biology.

Is It Safe to Limit Calories Over Long Periods of Time?

Consult your doctor before beginning any kind of calorie-restrictive diet, advises Justice. Since there are risks involved, she advises that it should be carried out with professional supervision.

According to Julia Zumpano, RD, from Cleveland Clinic’s Center for Human Nutrition, cutting calories is typically safe as long as a person is consuming the required quantity of nutrients, unless they are already underweight or could become underweight as a result of the caloric restriction.

To build a plan and ensure they are fulfilling all nutritional needs, she advises that a person first consult a licensed dietician.

“I would suggest limiting the number of calories consumed from empty-calorie foods and beverages” (very little to no nutrients). Zumpano lists a few examples: soda, sweetened coffee beverages, punch, lemonade, sweets, pastries, and cookies; fast food; chips; sour cream; creamy salad dressings; and cream cheese.