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Low-Calorie Diet Has Unexpected Effect on Aging

Caloric restriction may extend human lifespan through reduced oxidative stress that can damage DNA.

Pandora Dewan, Newsweek, Apr 18, 2024

Our diets play a key role in the way our bodies age, but the relationship between the two is much more complicated than we once thought.

Numerous studies in animals have shown that restricting calories can increase longevity. Indeed, calorie restriction also appears to reduce various signs of aging in humans too.

"There are many reasons why caloric restriction may extend human lifespans, and the topic is still being studied," Waylon Hastings, a postdoctoral researcher at the Tulane School of Medicine who earned his doctorate in biobehavioral health at Penn State, said in a statement. "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."

To replace these worn-out cells, our bodies need to create new ones - and this requires copying the DNA present in the existing cells.

Our DNA is like a shoe lace - at the end of each strand is a molecular "cap" that protects it from becoming frayed or tangled. These caps, called telomeres, become slightly shorter every time the DNA is copied to produce new cells. And so the length of our telomeres is a useful indicator of the biological age of our cells.

Age, stress, illness, diet and genetics can all influence how often our cells replicate, and thus how quickly our telomeres shrink. But the impact of calorie restriction on human telomeres is less well understood.

To explore these effects, Hastings and colleagues at Penn State collected data from the national CALERIE study - the first randomized clinical trial of calorie restriction in humans. The team analyzed data from 175 participants after 24 months of caloric restriction.

"We hypothesized that telomere loss would be slower among people on caloric restriction," the study's senior author Isan Shalev, an associate professor of biobehavioral health at Penn State, said in a statement.

However, what they found was less black and white. After one year of caloric restriction, the participant's actually lost their telomeres more rapidly than those on a standard diet. However, after two years, once the participants' weight had stabilized, they began to lose their telomeres more slowly.

At the end of the two-year period, those on calorie-restricted diets had roughly the same length telomeres as those on a standard diet.

"This research shows the complexity of how caloric restriction affects telomere loss," Shalev said.

Further research is required to determine whether an additional year of restricted calories would create a statistical difference in biological aging between the participants. However, despite the ambiguity of these results, and the complex relationship between calorie consumption and telomere length, the CALERIE study has highlighted numerous other benefits of calorie restriction on human health, including reduction in "bad" cholesterol and blood pressure.

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