Four out of 10 teenagers with Eating disorders such as anorexia and Bulimia visit pro-eating disorder web sites devoted to helping people lose weight and hide the disorder from friends and family, according to new study findings.

“A large percentage of kids with eating disorders are using, or have used, these sites,” said study author Dr. Rebecka Peebles of Stanford University in California.

These web sites could hurt teens by triggering unhealthy attitudes and behaviors, which may worsen their disorders, Peebles noted.

Pro-eating disorder web sites typically include advice such as tips on weight loss and body weight goal charts.

As part of the study, Peebles and her team asked 52 teenagers with eating disorders and 77 of their parents to complete surveys about eating disorders.

They found that 40 percent of teens with an eating disorder had visited a pro-eating disorder web site, and about one-quarter said they had visited the sites frequently.

Only 34 percent of teens said they had visited web sites that discuss how to overcome eating disorders.

There was also a large “overlap,” Peebles noted, in which many individual teens visited both types of web sites, suggesting that there is a subgroup of teenagers who are “very curious to learn about their eating disorder from all different sources.”

More than 60 percent of teenagers who visited pro-eating disorder sites said they tried new weight loss tips or diet aids as a result - as did one quarter of teens who logged onto sites devoted to recovering from eating disorders.

In an interview, Peebles explained that recovery sites often include chat rooms, where teens can learn tips from each other on how to perpetuate the disorder, which may explain why the sites’ good intentions can sometimes backfire.

Teenagers who visited sites that encouraged eating disorders tended to spend less time on schoolwork, and more time in the hospital than teens who didn’t visit the sites.

However, teen visitors to these sites did not weigh differently than other teens with Eating disorders, and were no more likely to experience complications such as Osteoporosis.

Parents of visitors to these web sites were more likely to know the sites existed, but many did not know their kids did, too, Peebles noted. Parents often “weren’t aware that their very own children were using these sites,” she said.

Peebles and her colleagues presented their findings Monday at the annual meeting of the Pediatric Academic Societies in Washington, DC.