Only regular exercise can help turn back the clock

of physical activity compared with those who had sedentary lifestyles – as well as those who managed moderate amounts of exercise.

Each time a cell replicates, a person loses a tiny bit of these endcaps.

So the older they get, the shorter their telomeres.

Prof Tucker found adults with high physical activity levels have telomeres with a biological ageing advantage of nine years over those who are sedentary. They had a seven-year advantage compared with those who are moderately active.

He said: “If you want to see a real difference in slowing your biological ageing, it appears that a little exercise won’t cut it. You have to work out regularly at high levels.”

His study, published in the journal Preventive Medicine, analysed data from 5,823 adults who participated in the US government’s National Health and Nutrition Examination Survey, one of the few that includes telomere lengths for subjects.

Although the exact mechanism for how exercise preserves telomeres is unknown, Prof Tucker said it may be tied to inflammation and oxidative stress.

Previous studies have shown telomere length is closely related to those two factors and it is known that exercise can suppress inflammation and oxidative stress over time.