Starving to live the fast dieting craze: a feast or a farce?

The introduction of Chai Zheng, 29, of Beijing, to the 5:2 diet plan was a little less dramatic. She says she started intermittent fasting soon after she came across a book on the subject in summer last year.

"When you really think about it, what the book says makes absolute sense," she says. "If you keep eating a lot of food, the digestive tract cannot remain clean, and the body is overtaxed."

One of those in the vanguard of the current crop of intermittent fasters was Xiao Yu, 27, of Shanghai, who went on an intermittent fast diet in 2012, when she was on a postgraduate program in the United States.

Xiao says that she had always had an appetite that was too big to be healthy, and that with the pressure of schoolwork and a sedentary collegiate lifestyle it was not only her academic knowledge that continued to expand but her waistline as well.

When she first heard about intermittent fasting, she says, she was immediately drawn to it.

"It has always been impossible for me to remain focused when I am hungry, and that's what I liked about intermittent fasting as soon as I found out about it. It lets me eat normally when I'm fasting and is much more do-able than those long-term diets where you have to do without stuff every day."

In her diet regime, she was allocated three consecutive days in a month to fast, during which she was limited to consuming salad or juice.

Because she was busy with studies, she says, she had limited energy to prepare low-calorie food herself, so she often bought bottled juice online to fulfill her needs.

In the US the bottled juice industry has long been geared to the needs of those on fasts, serving products that are low on calories and high nutrition, Xiao says.

When Xiao first took up intermittent fasting, the desire for food was torture, she says, more in the realms of psychological craving rather than physical need.

However, after several months on her three-days-a-month fasting regime, the benefits began to become clear, she says.

Not only did she lose weight, but "my sense of smell and taste became sharper, and I would subconsciously abstain from oily and salty food", Xiao says.

Her digestion and bodily functions also improved markedly, she says.

But when she returned to China in 2013, similar products were difficult to find, and she had to modify her fasting plan.

One day a week she would satiate herself with regular food in the morning, eat little at lunchtime and have a vegetable salad or no food in the evening.

Early last year, she says, she noticed that in China juice makers seemed to be catching up with their counterparts in the US, offering greatly broadened ranges of juices.