Du Hei, 40, who lives in Xi'an, Shaanxi province, says he and his wife have eaten light food at weekends for more than six years.

When they are home at the weekend they avoid meat and oil and often have lightly boiled vegetables dressed with a little salt and sauce, and steamed yams and potatoes, because such food is low in calories and high in rich fibers, Du says.

The reason they eat low-fat, low-calorie food at the weekend is that they eat too many calories on weekdays. A multitude of rich fibers at the weekend will cleanse their digestive tracts, and taking in fewer calories will help them control their waistlines, he says.

Du says TV health experts who say people should consume more vegetables and less meat inspired their light diet.

The Taoist tradition of bigu, literally avoiding grains, a fasting technique associated with achieving immortality in Taoism, also inspired them, Du says. In fact, many Chinese people who hear about intermittent fasting associate it with bigu.

It was only recently that Du could attach the moniker intermittent fasting to his regimen when a relative told him about the BBC documentary film and the 5:2 diet.

"But it doesn't really matter how I started this healthy eating pattern," he says. "What matters are the benefits I can show for it."

Over the years, he says, his cholesterol levels and blood pressure have remained normal.

Hilary Hu, 26, a housewife in Shanghai, says she has been buying bottled cold-pressed juice regularly to replace meals since last summer.

She is enthusiastic about keeping fit, she says, and since her college years she has tried various ways to "cleanse my body and revitalize my health".

Four years ago she tried bigu after she read a book on how some Japanese cancer patients practice it, and in doing so increase their longevity. But it was too difficult for her to abstain from food completely and have water only for a whole day, she says.

The hunger pangs were unbearable and she could hear her stomach rumbling all day, and gradually she started having small quantities of noodles to relieve the hunger while practicing bigu.

When she heard about intermittent fasting last year, she took it up without a second thought, she says.

"Intermittent fasting sounds just like bigu, but it's easier to practice. In fact, it's like an upgraded, user-friendly version of bigu."

Hu says she has practiced intermittent fasting for about a year and also does yoga, and believes she is becoming healthier. She used to suffer from indigestion and neck ache, but now these have disappeared, and she is stronger.

Chai in Beijing, says she is still on an intermittent fast, but that it is a little different to what she had expected.

She bought bottled fresh juice online to fast not because she wanted to "cleanse my body", she says, but because she wanted to be healthier. But soon she found the juice upset her stomach, so she started eating porridge instead.

However, some nutritionists and health professionals do not share the unbridled enthusiasm that adherents such as Chai show for intermittent fasting.

Ma Guansheng, a nutritionist with the School of Public Health at Peking University, is cautious in talking about the health benefits that intermittent fasting can deliver.

"It's true that having low-calorie food regularly will help you lose weight, but it's stretching it to say such a diet can reduce the risk of disease and revitalize health. Any such assertions need to be based on solid experiments and research."

Britain's National Health Service takes an even more skeptical view. It brands the 5:2 regimen as a fad diet and says that "there is little or no evidence" to support claims that it can protect against disease and prolong life.

liuzhihua@chinadaily.com.cn