Runners should exercise at least five times a week to reap the benefits of going for a jog, new research has revealed.
Running five times a week could slow the ageing process by protecting against cell damage, according to the journal of Preventative Medicine.
However, infrequent exercise will not improve health, scientists warn.
Women would have to jog for 30 minutes five days a week - and men for 40 minutes - to reap the benefits.
The study of almost 6,000 people found high levels of exercise protect parts of DNA called telomeres, proteins on the end of chromosomes that are lost in the cellular ageing process.
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Professor Larry Tucker, of Brigham Young University in the US, said this may be linked to the suppression of inflammation and oxidative stress.
He said: “We know that regular physical activity helps to reduce mortality and prolong life, and now we know part of that advantage may be due to the preservation of telomeres.”
Professor Tucker discovered adults with a high level of physical activity had a "biological ageing advantage" of nine years compared to sedentary adults.
When compared with those who did a moderate amount of exercise, the age different for highly active adults was seven years.