Teens with eating disorders are picking up dangerous tips from both pro-eating-disorder web sites and sites designed to treat the problem, according to a new study.

And though most of their parents know about the pro-eating-disorder web sites, few sit down and talk to their kids about them.

The so-called "pro-Ana" web sites — shorthand for pro-anorexia — offer tips on extreme weight loss and purging. They suggest that believing one can't be too thin is a lifestyle choice, not an eating disorder.

The sites often offer strategies for avoiding detection by parents and doctors when purging.

Site forums allow teens with eating disorders to share tips and offer support.

These sites usually carry "thinspiration" pictures — sometimes shocking images of extremely thin young people.

How much do teens with eating disorders and their parents know about these sites? In an effort to find out, researchers surveyed families of patients age 10-22 treated at Stanford University's Lucile Packard Children's Hospital.

Underscoring the difficulty of studying the issue, researchers sent surveys to some 700 parents and 700 patients, but only 106 parents and 76 patients completed them. These included 116 parent/patient pairs.

Among those who returned the surveys:

—35.5 percent of patients said they'd visited pro-eating-disorder web sites.

—41 percent of patients said they'd visited pro-recovery web sites.

—48.7 percent of patients said they'd never visited either a pro-eating-disorder or pro-recovery web site.

—96 percent of patients who visited pro-eating-disorder web sites said they learned new techniques of harmful behavior.

—46.4 percent of patients who visited pro-recovery web sites said they learned new techniques of harmful behavior.

Pro-recovery web sites stress that eating disorders are life-threatening problems and point patients to health care and other resources.

But they also often offer support forums in which patients may share harmful weight loss or purging techniques.

In other findings:

—Slightly more than half the parents (52.8 percent) knew about pro-eating-disorder web sites.

—More than half the parents didn't know whether their teen had visited pro-eating-disorder web sites.

—Only 27.6 percent of parents discussed pro-eating-disorder web sites with their child.

"Given the activities that their children are reporting adopting after visiting both pro-eating-disorder and pro-recovery sites, it is important to educate parents further on how to be constructively but actively involved in their children's Internet use," suggest researchers Jenny L. Wilson and colleagues.

The study appears in the December issue of Pediatrics.

By Daniel J. DeNoon, reviewed By Louise Chang, MD

SOURCES: Wilson, J. Pediatrics, December 2006; vol 118: pp e1635-e1643. News release, Lucile Packard Children's Hospital, Stanford, Calif.