Researchers I interviewed recounted their taping sessions in kids' bedrooms, playing with toys or grooming. A ritual as private as bath time has become familiar territory as marketers observe children taking baths and showers to come up with strategies to sell new health and beauty products or find novel approaches for marketing existing ones. They investigate children's closets. They even go to sleepovers.

American parents have been well warned about junk food, how it dominates advertising aimed toward children and how poor eating habits have led a staggering 15 percent of the nation's children into obesity. They are told of the health risks and that a whopping one-third of children born today are expected to eventually develop diabetes.

But it's not just junk food that endangers the health of our children, it's also the "junk culture" that surrounds them. And not that junk culture not only is making children materialistic but is also making them sick. They are becoming depressed and anxious, my research shows. They are suffering from headaches and stomachaches, too.

We know our children are living in an environment where they are bombarded with advertising aimed just at them, but it is influencing them in more ways than their parents might imagine.

The average American child is exposed to 40,000 advertising messages each year, according to recent estimates, and corporations are spending $15 billion annually advertising and marketing to kids up to age 12. With all this money at hand, companies are ratcheting up their kid-oriented ad budgets to promote entertainment, fashion and apparel, electronics and furniture, and health and beauty aids. After more than a decade of relentless advertising and marketing to children, the results are striking.

By the time many children reach early elementary school, they have been incorporated into the universe of junk entertainment, listening to music and watching movies and television that offer them unprecedented levels of violence along with the presentation of young people as sexual objects. (MTV isn't just for teenagers; it's a kid phenomenon, too.)

By the time these kids enter the 8-to-12 "tween" stage, they've adopted the junk values of materialism and the desire to be rich. When I interviewed Martin Lindstrom, a branding expert, he cited a recent survey by the Millward Brown global market research agency. It reveals that nowhere else in the world are 8- to 12-year-olds more materialistic (75 percent desire to be "rich") or more likely to believe that their clothes and brands describe who they are and define their social status.

All this is not only distasteful, it is unhealthy, as I found after surveying 300 children ages 10 to 13 in urban and suburban Boston in 2002 and 2003.

I came to this conclusion by creating a new measure of the kids' level of "involvement" in consumer culture — in addition to their media exposure, which is the usual standard. I asked questions about how much they were psychically tuned in to the values and aspirations of consuming, such as how much they cared about having a lot of stuff; how important designer labels and a nice family car were to them; whether they usually were focused on acquiring something new; and how much they wanted to be rich and wanted their parents to be richer.

Among the suburban kids whose parents were more restrictive about consumer culture, I also found that the more they bought into that culture, the more negative they were about their parents, and the more likely they were to fight and disagree with them.

While the figures tell me children's well-being was affected by consumer involvement, they do not explain how. One possibility is that people who are envious of others and worried about possessions and money are more likely to be depressed and anxious. Desiring less — rather than getting more — seems to be the key to contentment and well-being. Perhaps, as they focus on the consumer culture, kids spend less time in reading and the play that keeps them happy and healthy.

Difficult as it is to explain, the connection is clear: The more enmeshed children are in the culture of getting and spending, the more they suffer for it.

As I interviewed children and parents, I found the conversations were supporting what the figures were telling me. Parents who were involved in conflicts with their kids about buying stuff, eating junk food, and watching TV, playing video games and using the Internet also reported that their children were experiencing behavior problems, difficulties in school and unhappiness.

How have things gotten so far out of hand? For the past decade, the kids junk culture has been relentlessly pushed by a small number of mega-corporations — Viacom, Disney, McDonald's, Burger King, Philip Morris, Coca-Cola, Pepsi, Sony Pictures and others. Through their advertising agencies, these companies have developed sophisticated and effective methods of reaching children that go far beyond the television ads of yesteryear.

That kind of intensive research went into companies figuring out they could turn shampoo bottles into licensed character toys, plastic first-aid bandages into "tattoos," and ketchup into a gross green goop that kids will demand. Marketers have also perfected stealth marketing efforts, such as "peer-to-peer" campaigns that enlist kids to market to their friends and schoolmates, a process that has been gaining popularity recently.

Language provides a particularly telling clue to the marketers' mentality. It's a war out there. Children are referred to as "targets." Printed materials are "collateral"; grass-roots campaigns are "guerrilla" or "viral." Sometimes they talk about "converting (a kid) into a user," a phrase from the drug culture. There's little doubt about who's winning this war either, as marketers have transformed childhood from an idyllic to a hazardous life stage. It's high time parents and legislators took notice and countered the growing culture of junk.

Findings like mine, as well as those of many other studies that document the harmful effects of the individual components of the junk culture — food, violent video games, oversexualized body images, and youth consumption of drugs, tobacco and alcohol — suggest that adults are failing to protect children in basic ways.

Many adults respond to the junk culture with a fatalistic attitude, shrugging it off as inescapable or not essentially different from what they experienced as children. But others are breaking through that denial to push legislative agendas that pursue new protections from advertising, such as the Parents' Bill of Rights, a set of nine measures to reform marketing practices being sought by Commercial Alert, an organization based in Portland, Ore. Other groups advocate school-based measures such as district-wide prohibitions against soft-drink contracts in schools.

Industry is fighting back, by dominating government panels, providing stepped-up financial contributions to politicians and advocacy groups such as the National PTA and funding industry front groups such as the Center for Consumer Freedom. But with mounting evidence of the harm being done to America's children by the junk culture, it's high time parents, educators and children's advocates stood up to the junk purveyors and reclaimed the culture of childhood.