WASHINGTON - It's the latest weight loss craze among American 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 say the cost of what teens see as an ideal body shape - but really is for most unattainable - is self-esteem problems that can 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.
"My thigh gap is huge," brags a Tumblr user with the handle foster-the-beatles.
Another user, skinnysizezero, cheers her fellow dieters on, saying: "Together we can lose weight. Together we can be skinny."
"Together we can be a size zero with a beautiful thigh gap and flat stomach. Together we can be happy and finally say that we love our bodies," her post pledges.
Another poster, elleskyyy, said she felt better when she "realised I'm getting a thigh gap."
Meanwhile, a user called "starving for perfection" complained about her "mediocre/nonexistent thigh gap" and flagellated herself for her "fatfatfatfat."
Experts say the obsession with leg shape is not new, but has been dramatically amplified by social media websites and their 24/7 influence on the lives of American teens.
The fan Twitter account Cara's Thigh Gap, is dedicated to the extreme slenderness of British model Cara Delevingne, while dozens of Facebook pages and websites propose diets and exercise regimes to achieve the almighty gap.
But clinical psychologist Barbara Greenberg warned that for most women, the "thigh gap" is a pipe dream, even via extreme dieting and exercise.
"Most women are not built that way to have that space between their thighs," she said.