THURSDAY, June 17 (HealthDay News) -- They're out there on the Web: Sites that offer tips to successful purging or water-only fasts; others that list methods of hiding rapid weight loss from parents and doctors.

If the proliferation of these pro-anorexia and pro-bulimia Web sites isn't bad enough, eating disorder experts say they now have to contend with "pro-ana" and "pro-mia" bloggers and "thinspiration" Twitter updates sent right to an interested party's mobile phone.

"They are reaching very vulnerable youth," said Dina Borzekowski, an associate professor in Johns Hopkins Bloomberg School of Public Health. "When you have the Internet used all times of the night, kids have easy access to it. It's anonymous. They can gain support for what they're doing and information."

For their new study, Borzekowski and colleagues conducted a systematic review of 180 pro-eating disorder sites. What they found was both surprising and frightening.

About 91 percent of sites were open to the public -- though many warned that "wannabes" should stay away -- and about 79 percent had interactive features, such as calorie and body-mass index (BMI) calculators.

About 16 percent had a "creed" or "oath to Ana," such as the "Thin Commandments," or 10 rules for eating disorders, such as: "Thou shall not eat without feeling guilty," "Thou shall not eat fattening food without punishing oneself afterward," and "What the scale says is the most important thing."

About 42 percent provided a venue for posting artwork and poetry, some of it disturbing:

"some look at us and call us crazy
how little they really know
they pass us by and stare
like we're in some sickly show
don't they see?
It is not us who is at fault
They kill their bodies with fats and grease
but we give our bodies nothing at all."

"Thinspiration," such as photos or videos of very thin models and actresses, were on 85 percent of the sites. And about 43 percent provided specific instructions on concealing eating disorders, according to the study.

Patients with eating disorders have been known to go to great lengths to hide their weight loss, explained Dr. Ira Sacker, an eating disorder specialist, including drinking lots of water before being weighed and hiding weights in their clothes.

About one-third of sites did include information about recovery or treatment, though only 13 percent of sites contained an overt statement that eating disorders are a problem.

"Some people who create these messages stand behind what they are doing, while another fraction realize this is troubling and they are suffering," Borzekowski, said. "You get mixed messages."

The study is published in the June 17 issue of the American Journal of Public Health.

Previous research suggests that teens exposed to pro-eating disorder Web sites do have higher levels of body dissatisfaction compared to adolescents that have not been exposed. Other studies found that teens who spent time on these sites tend to have harder-to-treat eating disorders, according to background information in the study.

Sacker has been treating patients with eating disorders for some 40 years. He can remember his dismay when he first started seeing pro-eating disorder sites pop up in the early 1990s.

"These are really scary," Sacker said. "The people on these sites want to be using the eating disorder as their identity, and they want to communicate with others like them. That makes them believe there is a safety in it and a community behind it, which reinforces that what they are doing is OK. It's almost like a cheerleading group."

In 2001, the search engines Yahoo and MSN agreed to shut down overtly pro-eating disorder sites, according to background information in the article.

It didn't make much of a dent, Sacker said. Over time, online offerings for those with eating disorders have only gotten more sophisticated. The text and a photos of skeletal models has morphed into videos, voice-overs, blogs and Facebook groups.

"Parents need to be aware and have boundaries about what their kids are doing on Facebook or on these sites," Sacker said. "Even though some sites talk about recovery, the majority can worsen or prolong the illness."

Though there are many exceptions, the typical profile of someone with an eating disorder is a highly intelligent, motivated perfectionist who "feels they are not good enough, no matter what they do, and are looking for some form of control," Sacker said.

The content of pro-eating disorder sites reflected those themes, with 83 percent talking about "success," 81 percent "control," 80 percent "perfection" and 76 percent "solidarity," according to the paper.

People with eating disorders may also have depression, anxiety and obsessive-compulsive disorder or other mental health conditions.

The obsession with weight loss obscures all else, Sacker said. "They become totally preoccupied by looking at mirrors. They know more about nutrition than most nutritionists. They lose friends and become socially isolated because of it," Sacker said.

Medications, including mood stabilizers, anti-anxiety drugs and antidepressants can help some with eating disorders, Sacker said.

More information

There's more on eating disorders at the American Academy of Family Physicians.