In a study published yesterday by the Kaiser Family Foundation charity, corporate websites including Kellogg's, Wrigley's, General Mills, PepsiCo and Nestle were found to encourage children to interact with brands in more personal and detailed ways than other conventional advertising modes.
As companies increasingly blur the lines between adverts and entertainment on their sites, US policymakers in Congress, the Federal Trade Commission and the Institute of Medicine are studying the report and have vowed to address the issue.
The study found 73 per cent of websites used "advergames" featuring brand products or characters, while 64 per cent used viral marketing techniques to push children to contact their peers about specific products.
To encourage additional time spent at the websites, 71 per cent of games promote repeat playing, 45 per cent offer multiple levels of play, and 22 per cent suggest other games the visitor might enjoy.
Other devices such as sweepstakes and promotions were also found to be popular with online food marketers.
"Online advertising's reach isn't as broad as that of television, but it's much deeper," said Vicky Rideout, director of KFF's Program for the Study of Entertainment Media and Health.
"Without good information about what this new world of advertising really looks like, there can't be effective oversight or policymaking, whether by the industry or by government," she said.
The study includes detailed analysis of 77 websites, covering more than 4,000 unique web pages. Based on data from Nielsen NetRatings, these sites received more than 12.2m visits from children ages two to 11 in the second quarter of 2005.
However, all websites were found to operate in accordance with current Children's Advertising Review Unit (CARU) guidelines which insist on the display of nutritional and parental information.
The Grocery Manufacturers Association (GMA) senior vice-president Mary Sophos said the food industry has already taken great strides to combat obesity, with the reformulation of products and healthy lifestyle promotional campaigns.
"When it comes to children, we are especially cognisant of the need for responsible marketing practices. That is why we fully support the application of CARU's guidelines to all forms of advertising to children," she said.
In a similar study published earlier this year British consumer watchdog Which?, together with the UK's Food Commission, identified more than 40 publicity tricks that use new media technologies to target children. The watchdog is now pushing the British government for tighter restrictions.
"It can be incredibly difficult to protect your child. While at home, shopping, playing and even at school, children are constantly bombarded with calculated marketing messages encouraging them to eat more junk food," said Which? chief policy advisor Sue Davies.
"Such reckless marketing undermines efforts to improve children's diets."
Collectively, the Kaiser Foundation's findings indicate that the world in which children encounter advertising is changing rapidly. On the internet the boundaries between advertising and other content is much harder for the child to distinguish.
The charity asserts is it important to understand what this relatively new marketing medium offers children, and is encouraging informed discussion on the subject.