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When I last wrote about the research I did on aging and exercise, I focused on one of the major ways biologists can tell where a person is in the aging process: the epigenetic clock. I described a process called DNA methylation, signals that tell certain genes to whether to become active or not.
This time, I’m going to focus on another major hallmark of aging: telomere shrinkage. (For more detail, check out my latest book, Exercise is Medicine, from Oxford University Press.) Telomeres are tiny bits of DNA on the ends of chromosomes, like those little plastic aglets on the ends of shoelaces. Telomeres keep the DNA from unraveling—frayed, unraveled telomeres would mess up the delicate process of cell division.
With aging, telomeres naturally get shorter, which ultimately means they are unable to keep DNA in good enough shape for the cell to divide properly. Whether shorter telomeres are just a sign of aging or an actual cause is not clear. And for the record, some scientists think the whole telomere story has been greatly hyped as an explanation for aging.
That said, it’s a hot area of research, including whether interventions like dietary changes and exercise can help keep telomeres strong and healthy.
In 2017, an exercise science professor at Brigham Young University named Larry Tucker stunned the community of researchers exploring the potential effect of exercise on telomeres.
Tucker’s study wasn’t the first time anybody had shown a positive association between exercise and longer telomeres in people, not just lab rats. Nor did it prove cause and effect. And it didn’t settle the question of whether exercise just maintains telomere length or might increase it.
But Tucker’s study of 5,823 adults aged 20-84 made headlines nonetheless. In his analysis of this large, random sample, Tucker showed that people who habitually exercised had much longer telomeres than sedentary folks—a difference that, if telomere length is truly a biomarker of aging, would be the equivalent to 9 years less cellular aging.
Other studies showed fascinating results, too. In a 2017 study of women whose average age was 79.2, researchers from the San Diego School of Medicine found that those who did more leisure-time physical activity had longer telomeres. In another San Diego study that tracked activity levels with accelerometers (Fitbit-like devices), older women who did at least two and a half hours a week of moderate physical activity had longer telomeres than those who did less.
In a third San Diego study, researchers found that higher sedentary time, as measured by accelerometers, may be associated with shorter telomeres.
To be fair, not all studies have lined up as expected. A South African study of marathoners found no difference in telomere length between marathoners and sedentary folk. Even a 2015 meta-analysis of more than 30 studies involving 41,230 people came up empty.
In other words, the idea that exercise can keep telomeres long is very much an open question. Nonetheless, I decided to go online and take a commercial telomere test. The independent scientists I had talked to warned me that the methodology used in these commercial tests is far inferior to that used in research labs. Still, I was curious.
I sent away for the test, pricked my finger, and sent the blood sample off to the company. A week or so later, the results came back: I was 10 years younger than my chronological age.
Too bad I can’t believe it. The commercial tests are just too unreliable.
