Could Calorie Restriction Slow Aging? New Research Shows a Link—But Experts Have Concerns

  • A recent study found that a 25% calorie reduction has the potential to slow the pace of aging.
  • While the study did discover positive results, it also noted the dramatic restriction as hard to maintain.
  • Experts suggest fasting in smaller amounts of time to yield similar results.

A recent study published in Nature Aging indicates that a significant calorie reduction may slow the pace of aging significantly—as much as quitting smoking.

Anti-aging, aging well, and slowing the aging process are popular topics in the wellness space. Hence the overwhelming amount of products that grace pharmacy shelves and social media ads. American life expectancy is remarkably higher than it was 100 years ago, but it’s not just the length of time you live that people are concerned with, it’s how you age as those years go by.

To have the goal of “slowing aging” is to focus on how people can maintain certain levels of comfort and health throughout their life.

There are many factors that go into how each individual experiences the aging process, nutrition and diet habits being one.

Calorie Restriction’s Effects on Aging

The new study, funded by the National Institute of Aging, examined the effect of a significant calorie reduction (25%) on 220 randomized adults with normal, non-obese body weight. The calorie-restricted group received prepared meals for the first month of the study—to help familiarize themselves with the recommended diet—as well as behavioral counseling. The non-restricted group received no guidance about diet and did not participate in counseling.

The meals individuals within the calorie restriction group received rotated through three different diets—a low-fat option, a Mediterranean diet, and a low glycemic load diet—after a month, they were left to choose their own foods that fell within the guidelines. The 25% reduction was based on the individual’s baseline level of caloric intake; a normally 2,000-calorie diet would be cut by 500 calories.

While the study did show that calorie restriction made a positive change on the pace individuals age, the extreme cut in calories—25%—proved challenging to maintain even for the study participants. Belsky noted that most participants reduced their calories by an average of 12% over the life of the study. Most participants successfully achieved the prescribed 25% reduction in the program’s first six months, with adherence diminishing over the rest of the trial period.

It’s safe to assume that if the study’s participants were unable to maintain the originally planned reduction, other individuals would also struggle with long-term reduction.

Cutting calories in a regular diet by a quarter can be tough. Mike Roizen, MD, Chief Wellness Officer Emeritus at Cleveland Clinic and author of the Great Age Reboot, agreed. Dr. Roizen noted that while continuous calorie reduction is difficult, shorter bursts can be effective and show great benefit. 

Dr. Roizen noted that there are six primary ways to change our rate of death and disability based on his research: 

  • Normalizing blood pressure
  • Normalizing LDL cholesterol
  • Normalizing fasting blood sugar
  • Normalizing hemoglobin A1C
  • Normalizing weight in relation to height
  • Managing stress

Dr. Roizen suggested that short bursts of calorie reduction may be more attainable than a long-term, more intense calorie reduction. This concept is also championed by Valter Longo, PhD, a professor of gerontology and biological sciences and the Edna M. Jones Chair in Gerontology at the University of Southern California-Los Angeles, as well as director of USC’s Longevity Institute.

Longo’s research shows that a diet mimicking fasting can help prevent cancer, promote regeneration in those with autoimmune diseases, and reverse diabetes. But instead of cutting calories forever, Longo recommends a quarterly five-day reduced calorie regimen—Dr. Roizen has successfully used this method for seven years.

The first day of the fasting-mimicking program allows 1,000 calories, with the following four days totaling 750 calories each. Not only does the diet limit calories, but it encourages eating mainly vegetables with lean protein, such as fish. Dr. Roizen said that the fast is easily achievable and shows significant results.

 What Is Intermittent Fasting?

How to Measure the Pace of Aging

Measuring the pace of aging is far from a simple process. In order to have a well-rounded view of how fast or slow someone was aging, researchers need to analyze the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE) with three different clocks: the DunedinPACE, PhenoAge, and GrimAge.

Measuring Aging

  • DunedinPACE: a blood test used to measure the pace of aging.
  • PhenoAge: calculated based on an individual’s age and certain biomarkers that allow researchers to distinguish their “biological age.”
  • GrimAge: calculated based on an individual’s age and biomarkers that provide a biological mortality timeline.

Researcher Daniel Belsky, PhD, assistant professor in the department of epidemiology at the Robert N. Butler Columbia Aging Center, developed the DunedinPACE, which he describes as a “speedometer.” 

“The other two tests [PhenoAge and GrimAge] measure biological age—like odometers in your car. They tell you the distance traveled,” Belsky says. “But the DunedinPACE clock is a measure of the pace of aging. It tells you how fast you’re going. So one interpretation of the results is that the intervention was significant enough to slow the pace of aging. Still, it didn’t accumulate substantial impact on biological age over the two years.”

The DunedinPACE clock measures the pace of aging, whereas the PhenoAge and GrimAge address the cumulative effects of aging.

Downsides to Calorie Restriction 

Caloric restriction, even in small amounts such as Longo’s fast-mimicking diet or intermittent fasting, may provide positive aging benefits. But it’s crucial for restrictions to be conducted in a safe environment, ideally with the supervision and support of a medical professional.

While some individuals may benefit from a mild calorie reduction, the idea of long-term calorie reduction could also trigger disordered eating for certain people. An additional concern is whether or not restricting calories would allow individuals to meet all their nutritional needs—this takes thorough planning. Study participants were given detailed instructions on what to eat amidst their restrictions—the average individual may not have the same level of support and guidance.

Before beginning any dramatic change in your nutrition plan, it’s best to speak with a healthcare professional to review any questions or concerns you have.


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