St. Louis, Mo. -

Experts in eating disorders are concerned about an Internet-fueled trend in which teenage girls and young women pursue an elusive and possibly dangerous weight-loss goal: to become so slender that their thighs don't touch even when their feet are together.

Specialists say achieving a so-called thigh gap is risky and virtually impossible. But some exceptionally thin models have a gap, which is upheld as a beauty achievement on countless websites, blogs and other social media.

Doctors and counselors worry that the trend is contributing to a growing number of teens and 20-somethings with disorders such as anorexia.

Dr. Vonda Wright is a Pittsburgh-based orthopedic surgeon and fitness expert. She says the spacing between a person's legs is based mostly on genetics. And even many thin people can't achieve a gap.