Desperate Housewives and other TV soap operas may help make adolescent girls desperate for a thinness few can healthily achieve, new Australian research suggests.

The study of nearly 1,500 8th-to-11th graders also found that boys who watched music videos were at higher risk of developing the emerging male version of body-obsession -- a drive toward lean, hyper-muscular physiques.

The findings break new ground because they show that "it is not how much TV adolescents watch, it is what they watch that is bad for them," according to body-image expert Helga Dittmar, a senior lecturer in psychology at the University of Sussex, in England.

"In addition, this study is the first to give insight into several underlying psychological processes explaining how TV has this negative impact," said Dittmar, who was not involved in the research.

The study, conducted by Marika Tiggemann of Flinders University of South Australia in Adelaide, appears in the current issue of the Journal of Social and Clinical Psychology.

According to Dittmar, media pressures on young people to look thinner (for girls) or more pumped-up (for boys) have never been stronger.

"The media is getting worse," she said. "There's good evidence that the female ideal has become progressively thinner, so that typical female models are now often as much as 20 percent underweight (with 15 percent underweight a diagnostic criterion for anorexia nervosa)."

For boys, she pointed to the increasing bulk of children's action figures "that have become more muscular than even extreme bodybuilders."

For years, researchers have studied the effects of television viewing on children's body image, but those studies have come up with mixed results.

Tiggemann decided to tackle the problem from a different perspective, looking not only at kids' total viewing time, but what they watched and their stated reasons for watching.

In her study, Australian junior high and high school students filled out questionnaires detailing their previous week's TV viewing, including their motivations for tuning into particular shows. They also filled out standard tests aimed at measuring attitudes toward eating and body image.

Total time spent in front of the TV was not related to an unhealthy body image or attitudes that might heighten risks for eating disorders, Tiggemann reported.

However, "watching soap operas and, to a lesser extent, music videos, were associated with poorer body image," she said. "Although girls [were] worse off in absolute terms," Tiggemann said she saw the "same pattern of relationships for girls and boys."

Why might soap operas and music videos be particularly associated with a drive to extreme thinness or muscularity?

According to Tiggemann, music videos "present ideal styles of 'what's cool' that young people probably want to copy," while daytime and prime-time soaps "don't explicitly say people should look a particular way, but they show that being attractive and thin is associated with being rich and high status, etc."

Both of these scenarios are largely divorced from contemporary reality, she added.

Tiggemann noted that Australian soap operas tend to follow the American ideal, focusing on the struggles of the very rich and very thin. In fact, she said, "I think the most popular soap watched by young people is The O.C., and Desperate Housewives by slightly older folks."

The study also found that the reason a teen watched a particular show was very important to whether or not viewing was connected to body-image problems.

Watching TV for sheer entertainment was not related to body insecurity, whereas watching for what Tiggemann called "social learning" -- finding out about trends in behavior or fashion, for example -- was related, as was TV watching aimed at escapism or forgetting the day's troubles.

The Australian researcher said it's difficult to tease out a cause-and-effect relationship from these findings, because kids with body-image issues may simply be drawn to watching soap operas or music videos. "Most likely the influence goes both ways," she said.

Dittmar said the findings reflect the continuing power of media, especially American media, to influence lives.

"For example, in Fiji -- which had a full-bodied ideal for women -- girls quickly adopted the thin ideal after American TV was introduced," she added.

Of course, the vast majority of girls will not go on to become anorexic or bulimic, and most boys will not take dangerous steroids to build muscle. But Tiggemann believes television has the power to trigger insecurity and anxiety in everyone.

"Most people are perfectly healthy but cannot look like the TV stars without doing something unhealthy," she said. "As I see it, a whole heap of people are unnecessarily miserable about this and waste energy on something that is trumped up [by the media]. Here I'm talking about everygirl, everywoman."

Dittmar agreed, adding that the time to attack this problem is when children are young. "Not just parents, but educational programs in school, could help children and adolescents develop a more critical view of these ideals, and particularly mistaken beliefs linked with 'beauty' -- that it will make you happier and more successful," she said.