The challenge involves reaching around your back to touch your belly button, proving you're svelte enough to do so. The trend has been widely criticised for promoting unhealthy ideas about body image and triggering'thinspiration'. On top of this, it is not actually proof of good health, but a test of shoulder flexibility, not fitness.
Here are four other unhealthy body image challenges that have taken over social media:
Kylie Jenner challenge: Bizarre lip suction for pouty lips
The trend for fuller lips picked up pace lately with stars such as Kylie Jenner, who recently revealed it takes 40 minutes to makeover her massive pout.
The quest for the perfect pout then turned even more bizarre with a new trend in suction devices. The premise behind the device was a sucking action, causing lips to swell in size.
#Kyliejennerchallenge became a trending topic on Twitter with users taking to social media to show off the results of their attempt to supersize their pout.
However, it didn't come without some risks; the most common was cupping marks/hickeys and even bruising appearing around the lips.
#Kyliejennerchallenge became a trending topic on Twitter with users taking to social media to show off the results. Photo / Getty Images
Dangerous quest for 'thigh gap' - latest weight loss craze
This was a weight loss craze among teens striving to emulate the models they see in magazines - the "thigh gap", in which slender legs, when standing with feet together, do not touch.
Experts said cost of what teens see as an ideal body shape - but really is for most unattainable - was self-esteem issues that could lead to eating disorders, depression and even suicide.
On Tumblr, Pinterest and Facebook, "thigh gap" photos abound: close-ups of sometimes unbearably skinny legs published by young girls eager to show off their success - or bemoan what they see as a failure to whittle away fat.
The obsession with leg shape isn't new, but has been amplified by social media. Photo / Thinkstock
Bikini bridge becomes the new 'thigh gap'
First it was teens aiming for the perfect "thigh gap" in which a person would stand with their feet together, with slim legs showing thighs that do not touch.
Then came the "bikini bridge", which Urban Dictionary describes as "when bikini bottoms are suspended between the two hip bones, causing a space between the bikini and the lower abdomen."
Bikini bridge enthusiasts uploaded their own images to 4chan, an image sharing site, and a Twitter feed and Tumblr dedicated to the cause were established. The hashtag #bikinibridge began circulating on Twitter.
Mon pubis: A new body part for women to hate
With a new year, comes a new body part to hate - and fix. Make way for the "mon pubis", referring to the mound of flesh on the pubic bone.
Writing in The New York Times, Jennifer Weiner explained: "This year, the hot new body part is the formerly unnoticed span of flesh between the top of one's panties and the labia majora, currently displayed on the cover of the Sports Illustrated Swimsuit Edition by the model Hannah Davis."
The hashtag #Monspubis started to do the rounds on Twitter and plenty of forums were established, dedicated to women who to air their insecurities about the body part.
The 'mon pubis', which refers to the mound of flesh on the pubic bone is being hailed as the latest body part to feel insecure about. Photo / 123RF
It’s been an Onslow signature menu item since day one. Now, Josh Emett’s famous crayfish eclair has clawed its way into the Iconic Auckland Eats Top 100 list. Video / Alyse Wright
