STATE COLLEGE, Pa. — Penn State researchers are adding new compelling evidence that ties dieting to aging. Their study looked at telomeres, the genetic “end caps” which protect our chromosomes, and how calorie restriction affects them.
Publishing their findings in the journal Aging Cell, the team examined data from a two-year study of caloric restriction in humans, where the researchers found those who restricted their calories lost telomeres at different rates compared to the control group. Despite this, both groups finished the study with telomeres at nearly the same length. According to previous findings, restricting calories by 20 to 60 percent promoted longer life among several different animals.
Every time a person’s cells divide, some telomeres are lost when chromosomes are copied to a new cell. Then, the overall length of the cell’s telomeres is shortened. Over time, as cells continue to divide, the cap of telomeres completely goes away. The genetic information in the chromosome is then more susceptible to damage, preventing future reproduction or proper function of the cell. This is called cellular senescence.
In other words, cells with longer telomeres work as if they were “younger” than cells with shorter telomeres. So, two people who are the same age could have different biological ages based on telomere length.
Besides normal aging, stress, illness, genetics, diet, and other factors can impact how often cells replicate and how much telomere remains, per Idan Shalev, associate professor of biobehavioral health at Penn State.
“There are many reasons why caloric restriction may extend human lifespans, and the topic is still being studied,” says Waylon Hastings, who earned his doctorate in biobehavioral health at Penn State in 2020 and was the lead author of this study, in a media release. “One primary mechanism through which life is extended relates to metabolism in a cell. When energy is consumed within a cell, waste products from that process cause oxidative stress that can damage DNA and otherwise break down the cell. When a person’s cells consume less energy due to caloric restriction, however, there are fewer waste products, and the cell does not break down as quickly.”
The team tested the telomere length of 175 research participants using data from the start of the CALERIE study, which is the first randomized clinical trial of calorie restriction in humans, as well as one year into the study and the end over a 24-month period. Around two-thirds of the participants participated in caloric restriction, while the remaining participants were part of the control group.
Results showed that over the first year, participants who were restricting calories lost weight, and lost telomeres quicker than the control group. After the one-year mark, the weight of these participants stabilized, and the restriction continued for another year. During year two, participants restricting calories lost telomeres at a slower rate than the control group. At the end of two years, both groups appeared to have evened out, and the telomere lengths weren’t statistically different.
“This research shows the complexity of how caloric restriction affects telomere loss. We hypothesized that telomere loss would be slower among people on caloric restriction. Instead, we found that people on caloric restriction lost telomeres more rapidly at first and then more slowly after their weight stabilized,” says Idan Shalev.
Shalev adds that the results have sparked many more questions. For instance, what would have happened to telomere length if data had been collected for an additional year? The study participants are now scheduled for data collection at the 10-year mark, and Shalev says he is looking forward to analyzing the results at that time. Despite the lingering questions, Shalev believes there is promise for the possible health benefits of caloric restriction in humans.
A Dietitian’s Take
Calorie restriction has been well-documented to benefit weight loss and, therefore, other health markers such as blood pressure, blood sugar, and cholesterol levels. More research on the chromosomal level would be beneficial for nutrition and health science.
At the same time, it’s important to note that calorie restriction doesn’t need to be severe. The idea of eating the least amount possible as being the only way to lose weight has been a big diet message for decades. It has actually made weight loss and healthy living seem more complicated than it actually is.
It typically just takes a small calorie deficit to start losing weight. For the average person, even just a couple hundred calories (not eating one of the average snack bars) could kickstart things. You don’t need to restrict yourself to the point that you feel hungry often, miserable, or just unsatisfied.