Inside the halls of Congress, a pantheon of popular cartoon characters that advertise sugar-laden snacks and cereals has been the topic of heated debate -- all centered around food promotion. Some nutritionists, consumer advocates and others claim those foods are exacerbating the problem of childhood obesity.

This topic has been hot in nutritional and scientific circles since researchers found that 16% of American children and adolescents are overweight -- a 45% increase since 1994.

Moreover, a new study predicts Americans are eating themselves toward a precipitous drop in U.S. life expectancy over the next half-century.

"It has become a full-fledged epidemic," said Sen. Tom Harkin, D-Iowa, at a news conference. "Junk food ads are pervasive on TV and radio, in print media, on the Internet, on billboards, in movies and along grocery store aisles. Not even schools are safe havens anymore."

In addition to an array of child-friendly packaged foods and video games, Harkin displayed a photograph of a school bus advertising 7UP.

"Now school buses are traveling billboards for sugary drinks," he said.

Harkin said he intends to introduce legislation that would give the agriculture secretary the power to ban all "junk food" advertising in schools.

He also plans to offer a bill to restore the Federal Trade Commission's power to regulate marketing directed at children. That authority was largely taken away in 1980.

Furthermore, the food industry has come under pressure to improve the quality of its products and ease up on marketing campaigns directed at children.

Health experts have warned that the trend toward bigger waistlines among children poses serious medical risks as they get older, including diabetes, asthma and heart problems.

Though other experts have taken issue with the findings, the report in The New England Journal of Medicine estimates that obesity will shorten the average lifespan of 77.6 years by two to five years.

The Journal of the American Medical Association last year reported that the average blood pressure among children and adolescents has been rising. The average reading among black and Mexican-American children was two to three points higher than among whites, the study found.

The American Psychological Association, which has studied the effect of advertising on children, estimates that more than $12 billion is spent annually aiming products at them.

Jeff McIntyre, the association's senior legislative affairs officer, told the news conference that children under the age of eight "are easy targets for commercial persuasion," because they "lack the cognitive development to understand the persuasive intent of advertising."

To underscore the point, Harkin displayed a blow-up of a comment a Heinz executive made to The Wall Street Journal in 2001: "All our advertising is targeted to kids," said Kelly Stitt, a senior brand manager at the company. "You want that nag factor so that seven-year-old Sarah is nagging mom in the grocery store to buy Funky Purple (Ketchup).

"We're not sure mom would reach out for it on her own."

The Center for Consumer Freedom, a nonprofit coalition, issued a statement from senior analyst Dan Mindus that said, "There is simply no scientific evidence proving food advertisements contribute to childhood obesity, but there is an abundance of research showing that a lack of physical activity does, and this is where our efforts should be focused."

Between the new obesity numbers and the government's new dietary guidelines, the food industry has taken steps recently to improve both its image and the nutrition of some of its products.

"Over the past several years, food and beverage companies have launched numerous initiatives to address public concerns about obesity, including reviews of advertising and marketing practices," said Manly Molpus, president and CEO of the Grocery Manufacturers of America (GMA). "GMA members have introduced thousands of new and reformulated products that are lower in saturated and trans fats, sodium and sugar."

In addition, the vending machine industry, which has 16% of its 7 million machines in schools, has kicked off an anti-obesity campaign. It will use color-coded stickers to rate food by nutrition. Less-healthy products will be labeled "choose rarely."

Meanwhile, the Sugar Association plans to spend at least $3 million a year over the next three years to reduce the stigma on its product by promoting sugar use in moderation.

"Some companies have taken some modest, baby steps forward," Harkin said. "We need to take some giant steps."

Still, the advocates assembled by Harkin had little good to say about the industry's efforts. Susan Linn, of the Campaign for a Commercial-Free Childhood, said the food industry "constantly lays the blame on parents" and undercuts their authority.

As depicted in advertising directed at children, parents are either "absent, mean, ineffectual or stupid," she said. "In commercial land, the most competent adult is Ronald McDonald."