Can caloric restriction help you live longer? It's complicated

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We all know the adage "You are what you eat." But what about how much you eat? It turns out, caloric restriction (intentionally eating less) could play a fascinating - and complex - role in the aging process.

Researchers at Penn State University are diving into this mystery, and their recent study on calorie restriction has uncovered a surprising twist in how our bodies might respond to this dietary change. Could eating less hold a key to a longer, healthier life?

Telomeres and biological age

To understand the study, we need to get to know telomeres. Telomeres are repetitive sequences of DNA found at the very tips of our chromosomes. Chromosomes are the structures within our cells that house our genetic information.

Each time our cells divide, the telomeres get a bit shorter. This shortening is a natural part of the cell division process. Over time, our telomeres become progressively shorter.

When telomeres get too short, our cells lose their ability to function properly. Telomeres act as safeguards for the ends of our chromosomes, preventing important genetic information from being lost. Once telomeres become critically short, cells can become damaged and stop functioning efficiently.

Many factors, including stress, illness, and our lifestyle choices, affect the rate of telomere shortening. While telomere shortening naturally occurs, some factors can accelerate the process.

Generally speaking, shorter telomeres are linked to a higher "biological age". This means that your body's cells might be exhibiting signs of age that are more advanced than your actual chronological age in years.

Caloric restriction

Scientists have observed a fascinating phenomenon in many animal species: calorie restriction appears to be linked to a longer lifespan. Studies on various animals, from worms to rodents, have shown that restricting calorie intake can significantly extend their lifespans compared to those eating a normal diet.

These findings fueled the curiosity of researchers at Penn State University. They wanted to investigate whether this effect translated to humans as well. To explore this question, the researchers turned to data from the CALERIE study, a groundbreaking national research project.

CALERIE stands for Comprehensive Assessment of Long-term Effects of Reducing Energy Intake. It's the first long-term, randomized clinical trial designed to examine the effects of calorie restriction on human health.

Participants in the CALERIE study were divided into two groups: one group followed a calorie-restricted diet, while the other maintained a typical diet. The Penn State researchers specifically focused on analyzing data related to telomere length to see if calorie restriction impacted how quickly telomeres shortened in the study participants.

The unexpected results of caloric restriction

Instead of the expected outcome - a gradual slowing down of telomere loss in the calorie restriction group - the researchers stumbled upon some unexpected twists and turns.

Year one

Individuals following the calorie-restricted diet experienced both weight loss and an accelerated rate of telomere shortening compared to those eating normally. This was contrary to the researchers' initial hypothesis.

Year two

Once the weight of participants on the calorie-restricted diet stabilized, a change occurred. They began to exhibit a slower rate of telomere shortening compared to the control group.

The end result: A draw

After two years of the study, the average telomere lengths in both the calorie restriction group and the control group were surprisingly similar. These findings suggest a complex and dynamic relationship between calorie restriction and telomere dynamics.

The initial acceleration in telomere loss could be the body's response to a significant change in energy intake. Cells might enter a temporary state of stress while adjusting to the new dietary conditions.

Once weight stabilized in the calorie restriction group, the long-term benefits associated with reduced calorie intake may have kicked in. Lower levels of cellular waste products and oxidative stress (which can damage DNA) might contribute to the observed slowdown in telomere shortening.

However, it's possible that the two-year study period was not long enough to fully capture the potential long-term effects of calorie restriction on telomere length.

"This research shows the complexity of how caloric restriction affects telomere loss," said Idan Shalev, associate professor of biobehavioral health at Penn State. "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."

So, what's the takeaway?

The initial spike in telomere loss for the calorie restriction group was unexpected but could indicate a complex response happening in our cells.

The study only followed participants for two years. Researchers hope that a 10-year follow-up will reveal more about whether calorie restriction has a lasting impact on telomere length and, in turn, the pace of aging. While the telomere data isn't conclusive yet, calorie restriction has other proven health benefits.

"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 thatcan 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," said Waylon Hastings, lead author of the study.

Previous studies on CALERIE participants showed that calorie restriction can help reduce harmful cholesterol and lower blood pressure. Clearly, there's more to discover about how our bodies respond long-term to eating less.

Should you try caloric restriction?

While potential benefits exist, it's definitely not a one-size-fits-all situation. Restricting calories for an extended period should always be done under medical supervision.

This research sheds light on the intricate connection between what we eat and how we age. Could our dinner plate hold secrets to a longer, healthier life? Scientists are eager to find out.

The findings are published in the journal Aging Cell.

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