Marathon aficionados say no other sporting activity can quite match it with the challenges it presents to the powers of determination and perseverance. [Photo provided to China Daily]

He used to weigh 100 kilograms but now weighs 75 kg, and all round he is much healthier, he says. Apart from once being overweight, his immunity was weak and his blood pressure and cholesterol level were high, and he suffered from asthma, he says.

"If I were to give a score to the quality of my life before I got into marathoning it would be just three out of 10. Now I'm so happy and full of energy."

Zhang Lei, of Beijing, says marathon has greatly improved her life, too. Though she is 51, she looks as though she is in her 30s. Those youthful looks can be attributed to marathoning, she says

"Once I could barely have conceived of enjoying running, but now it's become one of the most important things in my life."

The turning point came one day in April 2014 when she realized she had become so fat she had outgrown dresses she once loved to wear, and at a friend's recommendation she downloaded an app that promotes marathoning as a way of losing weight and getting fit and staying that way.

On her first run it took her 36 minutes to cover 1.6 kilometers, she says, and at the end of it she was out of breath. At the time, the idea of managing to run 5 kilometers was like a pipe dream, she says. However, she increased the distances she ran ever so gradually, and within six months she had run a half marathon in Beijing.

Since then she has run in a dozen of marathons in China and elsewhere.

"Marathoning has really changed me," she says.

She now looks like a different person, with a trim figure, and always feels energetic, and her husband, inspired by her, has also taken up long-distance running.