If there is a global obesity epidemic, the US - the home of purported culprits from Coca-Cola to Frito-Lay to McDonald's - may be patient zero.

Yet as country after country starts to consider curbs on food advertising aimed at children, to counter the alarmingly elevated levels of obesity among children, the idea of introducing similar limits in America, once greeted with about the same enthusiasm that a junk-food junkie shows for a Weight Watchers diet, is gaining momentum.

Just as decades ago the consumer reformer Ralph Nader seized upon the poor crashworthiness of the Chevrolet Corvair to parlay his book Unsafe at Any Speed into a crusade against what were deemed Detroit's deceptive automotive marketing tactics, someone may soon emerge as the leader of a jihad against junk food under the banner: "Unbearable at Any Bite."

Senator Joseph Lieberman of Connecticut, one of the Democrats seeking to run against President Bush, last month demanded an investigation by the federal government into the marketing practices of food makers. Lieberman, known for his battles to have ads for video games, movies and music labelled with parental warnings, pledged that as president he would require food ads to include nutritional data to guide parents; seek a law compelling restaurant chains to add such data to their menus; and ban the sale of fat- and calorie-laden snacks to children via vending machines in schools.

"Foods that feed the obesity crisis are being peddled to our children as never before," Lieberman declared. "It's time to stand up to the companies marketing to children products that can be harmful to their health."

His attacks followed a report from the Center for Science in the Public Interest, which lambasted food marketers for their tactics targeting children. The report urged the government to prohibit ads for high-fat products if it can be demonstrated they are aimed at children. The CSPI has been successful in fighting food marketing directed at adults, especially when it exposed the fat content of edibles such as movie-theatre popcorn and Chinese-restaurant meals. So the expansion of its efforts to the children's realm can only be bad news for the junk-food fabricators and fast feeders.

Sometimes the food companies do themselves no favours. For instance, two commercials from a recent controversial campaign by Foote Cone & Belding for KFC, which made the unlikely argument that fried chicken can be "a fresh way to eat better", ran during shows on the Cartoon Network cable-TV channel. That brought them under the jurisdiction of the Children's Advertising Review Council, an organisation that is part of the US advertising industry's self-regulatory process.

Though KFC was able to brush off complaints against the campaign lodged when the spots ran during shows aimed at adults, it was a different story when the review council charged the company with misleading advertising because the commercials could, it said, "very well leave children with the wrong net impression about the overall nutritional qualities of KFC fried chicken".

KFC, chastened, removed the campaign from children's TV and a week later stopped showing the spots altogether, notifying the review council that "it has no plans to run these commercials in the future" anywhere.

Who's chicken now?