The marketing weight of SpongeBob SquarePants and other "spokescharacters" should be used to encourage children to eat a healthy, nutritious diet instead of sugary, greasy junk food, a new report by an Institute of Medicine committee said yesterday.

If there isn't a shift to promoting healthier foods in the next two years, Congress should consider mandating changes in both broadcast and cable television, said Dr. J. Michael McGinnis, committee chairman and a senior scholar at the institute, which advises the government about health concerns.

It's hard to curb children from wanting the things they see on TV, said Carol Wygonik, of Natrona Heights, whose 9-year-old daughter had an appointment yesterday at the weight management and wellness center at Children's Hospital. It's even more difficult when toys are offered with food purchases.

"All kids want to do is sit there and watch these shows and then they have all the commercials stuck in there," she said. "They don't need this stuff."

The Grocery Manufacturers Association, which represents about 90 major manufacturers of packaged foods and beverages, said that its members have begun to make healthy changes and would consider making even more improvements.

"We always believe more can be done," said spokeswoman Stephanie Childs. "Just because we're doing good doesn't mean we can't be doing better, and we believe at this point that legislation would be premature."

Some much-maligned fast-food restaurants are overhauling the way they market their products to children and the foods they promote.

McDonald's doesn't plan to switch to whole wheat buns anytime soon, said Walt Riker, the company's vice president of communications, but it has added salads and yogurt to its menu, and allows parents to pick apple slices instead of french fries and low-fat milk instead of sodas for their kids' Happy Meals.

The company also has begun discussing ways to use promotional figures such as Shrek as advocates for fitness and a balanced diet, according to Mr. Riker.

"Some companies and restaurants have recently taken constructive steps to develop and promote healthier choices for children," Dr. McGinnis noted. "[But] the turnaround required is so substantial, and the issues are so complex, that the full involvement and leadership of the food and beverage industry is essential."

For a start, kid-friendly spokescharacters should be used only to promote healthy foods, the report says.

SpongeBob, for example, has helped sell spinach and carrots as part of a Nickelodeon campaign with former President Clinton to get kids to eat healthy food. But SpongeBob also has appeared on ice cream, Pop-Tarts, candy bars, lollipops, Pez, brownies, Rice Krispie treats, macaroni and cheese, cheese crackers and other products.

He has plenty of company on candy shelves, where characters include Arthur, the Cat in the Hat, Bob the Builder, Clifford, Scooby Doo, Elmo, Spiderman and Dora the Explorer, to name a few.

After an extensive review of available research and marketing practices, committee members concluded that there is strong evidence that TV advertising influences food and drink preferences and purchasing requests of 2- to 11-year-olds.

Also, "new offerings targeted specifically at young people were introduced at a substantially faster rate than products aimed at the general population," Dr. McGinnis said. "The top four items that children ages 8 to 12 say they can buy without parental permission are high-calorie and low-nutrient foods and beverages."

According to the report, childhood obesity rates have tripled in the last 40 years. About 5 percent of 6- to 19-year-olds were overweight in the 1960s, but that was up to 16 percent in 1999-2002. Type 2 diabetes, once called adult-onset diabetes, has doubled among children in the last decade.

Ms. Wygonik had long been concerned about the weight of her daughter, Alexandra Reinhart, but when blood tests showed the girl has an elevated insulin level, her concern intensified.

Alexandra weighed 109 pounds when she went to her first appointment at the weight management center at Children's this past summer. As soon as she got home, she went through the cupboards to set aside high-fat foods she wasn't going to eat anymore.

Now, Ms. Wygonik and her daughter routinely read food labels to check the fat content. The doctor said yesterday that they had to start limiting her sugar intake, too. Alexandra has lost 9 pounds since August.

According to the institute's report, children 8 and younger don't understand the "persuasive intent of marketing messages" and those 4 and younger can't consistently distinguish between TV commercials and programs.

Kelly van Schaick, a behavioral health specialist at the weight management center, said the institute's recommendations are an important step forward.

One of the first things Dr. van Schaick suggests to parents of children with weight problems is that they cut television and computer time and encourage physical activity instead.

"As the pressure builds up with these kinds of reports and putting more of the onus back on marketers, they'll respond to that pressure," said Janice Seigle, strategic corporate initiatives director for Highmark. "[But] it's going to take work in all sectors to really have an impact."

The company is working on getting better nutrition education into local schools, such as a Web-based demonstration project that allows body mass index tracking.

Highmark client data indicates that 39 percent of 13- to 18-year-olds are overweight, Ms. Seigle said.

"We know it's much harder for individuals to lose weight once they're overweight than to prevent it in the first place," she said.