A quick jaunt to Fun K Town can mean hours of online gaming fun for children, from skydiving onto a tropical island to viewing a series of "swashbuckling" video clips, a la "Pirates of the Caribbean."

The only catch: The island is CinnaIsland and the adventuresome pirate is Toucan Sam, both connected to the sugary breakfast cereals Apple Jacks and Froot Loops.         

Produced by Kellogg Co., Fun K Town is one of a number of Web sites maintained by food companies that target children under age 12. It's a trend that increasingly blurs the line between advertising and entertainment, according to a report released yesterday by the Kaiser Family Foundation, which studied 77 food company Web sites geared toward children.

The study came after recent reports by the Federal Trade Commission, the Department of Health and Human Services and a national science advisory panel that called on food and beverage companies to curtail television advertising of unhealthful foods in the wake of increased childhood obesity and diabetes.

"Online advertising still lags far behind television, but it is growing rapidly," said Vicky Rideout, a vice president of the Kaiser Family Foundation. "It's a field that's really changing at a breakneck speed."

The foundation's findings made no connection between the Web sites and the estimated 16 percent rate of childhood obesity. Researchers said the goal was to get an initial snapshot of a rapidly growing form of advertising.

Of the top 96 food brands advertised during children's television programming, 85 percent had a parallel Web site that directly targeted children, the study found. Many of the Web site addresses are included in television commercials or on cereal boxes, often packaged with some type of online promotion.

A majority of the sites had games, videos and sweepstakes aimed at younger children, including Lucky's Magical Realm, a "Lord of the Rings"-style video and game site centered on the marshmallow-y Lucky Charms cereal. About two-thirds of sites also used techniques such as "viral marketing," whereby users can pass on Web sites to friends. On Keebler's site, users were prompted to share the "Elfin Magic" of the company's trademark elves, while the Apple Jack page encouraged patrons to "share the island groove, mon."

"When you get on the Internet, this is by definition an interactive process," said Elizabeth Moore, an associate professor of marketing at the University of Notre Dame who led the study, "so the nature of the experience is much more in-depth, much more engaging."

Experts said that the Web is much more fluid than television and that the separation between programming and advertising is not as clear.

"Children below the age of 8 have a unique vulnerability to commercial persuasion," said Dale Kunkel, a professor of communication at the University of Arizona and a member of an Institute of Medicine committee that studied the effects of marketing food to children. "They don't understand the inherent persuasion and bias."

Oversight of the Internet is not as clear-cut as it is with television. In 2004, the Federal Communications Commission made a tentative ruling that would prohibit linking commercial content from children's programming on interactive digital cable systems, which could lead viewers to the Internet. But the FCC cannot regulate the Internet on its own.

The Children's Advertising Review Unit, the food and advertising industry's self-regulatory body aimed at kids commercials, is looking at more stringent requirements on Internet advertising. It has pursued cases in which content is deceptive or inappropriate for certain ages.

"We don't see this as an either-or proposition," said Nancy Daigler, a vice president of corporate and government affairs with Kraft Foods Inc. "We think you can be a responsible marketer and provide some fun for kids."

Kraft has stopped advertising less-nutritious products during children's programming on television and the radio and will phase out such advertising on the Web by the end of the year, Daigler said. The switch has resulted in a decrease in demand for certain products, she said.