Calorie Restriction Study Reveals Complexity of Diet’s Effects on Aging
It has long been known that calorie restriction, i.e. eating less, can prolong life by reducing metabolism and oxidative stress in cells. Reducing calorie intake also improves insulin sensitivity and blood sugar levels, factors associated with chronic disease and aging. Additionally, animal studies have shown that limiting calorie intake can activate biological pathways that protect against cell breakdown. Although further research in humans is needed, preliminary evidence suggests similar effects.
Researchers at Penn State University may have uncovered another layer of complexity to the mystery of how diet affects aging. A new study led by researchers at Pennsylvania State University’s College of Health and Human Development examined how calorie restriction affects a person’s telomeres (sections of the genetic makeup that function like the ends of shoelaces, protecting the ends of chromosomes from them to “unravel” during division). .
Analyzing data from a two-year study of calorie restriction in humans, researchers found that people who restricted their calorie intake lost telomeres at different rates than the control group, even though both groups ended the study with telomeres of approximately the same length. According to previous research, reducing calories by 20 to 60% has been shown to extend the life expectancy of many animals.
Telomeres and aging
Throughout human life, every time a person’s cells replicate, some telomeres are lost as chromosomes are copied into the new cell. When this happens, the total length of the cell’s telomeres shortens. When cells multiply enough times, the protective layer of telomeres completely dissolves. Then the genetic information of the chromosome can be damaged, preventing future reproduction or the correct functioning of the cell. A cell with longer telomeres is functionally younger than a cell with short telomeres, meaning that two people with the same chronological age could have a different biological age based on the length of their telomeres.
Typical age, stress, illness, genetics and diet, among other factors, can influence how often cells reproduce and how long telomeres last, said Idan Shalev, an associate professor of biobehavioral health at Penn State. Shalev led researchers who analyzed genetic samples from the national CALERIE trial, the first randomized clinical trial of calorie restriction in humans. Shalev and his team wanted to understand the effect of calorie restriction on telomere length in humans. Because telomere length reflects how quickly or slowly a person’s cells age, studying it could allow scientists to identify a way that calorie restriction could slow aging in humans.
“There are many reasons why calorie restriction can extend human life expectancy, and the topic is still being studied,” said Waylon Hastings, who received his doctorate in biobehavioral health from Penn State University in 2020 and was lead author of this study. “A primary mechanism by which life is extended is related to metabolism in a cell. When energy is used in a cell, the waste products of this process cause oxidative stress, which can damage DNA and otherwise destroy the cell. However, when a person’s cells use less energy due to calorie restriction, there are fewer waste products and the cell does not decay as quickly.
Eat less, eat more telomeres
Researchers analyzed the telomere length of 175 research participants using data from the start of the CALERIE study, one year into the study, and the end of the study after 24 months of calorie restriction. About two-thirds of the study participants participated in calorie restriction, while one-third served as a control group.
During the study, results showed that telomere loss changed the course. In the first year, participants who restricted their calorie intake lost weight and lost telomeres more quickly than the control group. After one year, the weight of the calorie-restricted participants stabilized and the calorie restriction continued for another year. In the second year of the study, calorie-restricted participants lost their telomeres more slowly than the control group. After two years, the two groups had become closer and the telomere lengths of the two groups were not statistically different.
“This research highlights the complexity of how calorie restriction affects telomere loss,” Shalev said. “Our hypothesis was that telomere loss would be slower in people on calorie restriction. “Instead, we found that calorie-restricted people initially lost telomeres more quickly and then more slowly after their weight stabilized.”
Shalev said the results raised many important questions. For example, what would have happened to telomere length if the data had been collected for another year? Participants in the study are expected to collect data for a 10-year follow-up, and Shalev said he is eager to analyze that data once it becomes available.
Despite the ambiguity of the results, Shalev said the potential health benefits of calorie restriction in humans are promising. Previous research on CALERIE data has shown that calorie restriction can help lower harmful cholesterol and lower blood pressure. For telomeres, the two-year period was not long enough to demonstrate benefits, but they can still be demonstrated, according to Shalev and Hastings.
intermittent fasting
Although cutting calories can be uncomfortable for many people, there are steps that can help make it more bearable. One of these is intermittent fasting, around 16:8, where you can only eat for eight hours a day.
Intermittent fasting helps with calorie restriction by limiting the amount of time food is consumed during the day, thereby naturally reducing the total amount of calories consumed. When people only eat during certain time windows, they tend to consume less food than if they ate throughout the day. Not only does this ease a calorie deficit, but it can also improve hormonal and metabolic regulation, supporting the benefits associated with calorie restriction.
REFERENCE
Effect of long-term calorie restriction on telomere length in healthy adults: Analysis of the CALERIE™ 2 trial
