A new obsession amongst teenage girls, achieving the thigh gap — or space between the thighs when a woman is standing with her knees together — has become an unhealthy and dangerous trend.

A new and surprising body trend has become an obsession amongst young women — achieving the thigh gap. Some teens see the thigh gap, or the space between a woman’s thighs when she’s standing with her knees together, as a symbol of the “ideal body.” But what at what lengths are they going to achieve it?

Why Focus on the “Thigh Gap?”

Young women have always been flooded with images of people considered to be beautiful, but with the advent of social media sites such as Facebook, Tumblr and Twitter, there are more outlets than ever before for teens to see women with bony figures and a sizeable space between their thighs. It’s common for teens post “thinspiration” images like these and share their thoughts with friends, further fueling the obsession.

Because the thigh gap is one of the first of such obsessions across social media, its stronghold over young women is more powerful that it might have been decades prior, when being thin was still “in” but there were fewer places to find images promoting these body types.

The reason people are drawn to physical traits like a thigh gap stems from a theory called cognitive averaging, Al Aly, MD, FACS, spokesperson for the American Society for Aesthetic Plastic Surgery says. According to this theory, attractive faces or body types are closer to the average population in their makeup and are seen as more familiar and typical than bodies that deviate from this average.

“We are genetically programmed to be attracted to averages, which change constantly,” Dr. Aly says. “Women are now being faced with [thinness] and seeing people with this trait receiving accolades and appearing attractive to others.”

While the “ideal body” has changed from decades when actresses like Marilyn Monroe were considered to be the epitome of attractiveness, thinness has had a tight rope over our cognitive averages for the last 20 years, Aly says, making it easy for young women to see hundreds of images of models with thigh gaps and want one for themselves.

The Dangers of Obsession

From social media to magazines to television, the amount of beauty content, combined with a desire to be thin, has put more pressure on young people than ever before, says Beverly Hills plastic surgeon Harry Glassman, MD.

It’s a dangerous and tenuous age, Aly says, and can pave the way for an obsession over something like a thigh gap — an often-unattainable goal unless most women are below their normal weight. The health risks associated with dieting to these extremes include malnutrition, anemia, a change or stop in the menstrual cycle and development of bulimia or anorexia. Genetics also play an issue in achieving a thigh gap, as not every woman’s bone structure is set in a way that will naturally create one no matter how much weight she loses, Aly says.

The word “obsession” is also a red flag to plastic surgeons, Dr. Glassman says, and many doctors who see women with unhealthy obsessions won’t consider performing surgery o