BEIJING • In the latest beauty craze sweeping social media in China, women - and some men - are boasting that they are paper thin by posting photographs of their waists behind a vertical piece of A4 paper.

To qualify, the waist must be entirely hidden by the paper. A piece of A4 paper is 21cm by 29.7cm. Holding it horizontally is cheating.

With the hashtag #A4Waist and a handful of variations, the trend is attracting hundreds of photos and thousands of comments on Weibo and other social media networks. Even the People's Daily, China's Communist Party newspaper, is joining in.

Skinny-bordering-on-emaciated is a widespread standard of beauty for women, one that has been criticised as an unhealthy ideal.

Several commentators have found the A4 trend disturbing.

"Bodies don't need eyes staring at them," Ms Zheng Churan wrote on a piece of A4 paper that she held horizontally below her waist. "I love my fat waist."

"I find it completely stupid," Mr He Xiaobin, senior fashion features editor at the Chinese edition of GQ magazine, said in a telephone interview. "Everybody has a different frame and body shape."

The A4 waist challenge annoyed him, he said, for allowing "certain people to gain bragging rights, while leaving others in dismay".

Some who do not qualify are turning to humour for comfort. Can they substitute a different paper size, such as A3, which is 29.7cm across? Or measure a body part other than the waist?

User Zhai Ruoyi wrote on her Weibo site: "How can you have an A4 waist? I have A4 legs!"

The tiny waist has a long tradition in China, going back at least to King Ling of Chu, who ruled from 540 to 529BC. A passage from the Book Of Han, the history of the Western Han dynasty, reads: "The King of Chu loved a narrow waist. Many people at court starved to death."

This is not the first skinny craze to circulate on Chinese social media. An earlier one featured women posting photos of themselves wrapping an arm all the way around their waist.

NEW YORK TIMES