The number of obese and extremely obese young U.S. children seems to be on the decline, government researchers said on Friday.

The companies designated $1.79 billion for marketing to people ages 2 to 17 in 2009, compared with $2.1 billion in 2006. However, online and mobile marketing has grown by 51 percent during this time to $122.5 million.

The reduced spending is due to market pressure in light of concerns about a child obesity crisis in the United States.

The U.S. child obesity rate has almost tripled since 1980 to 17 percent, or 12.5 million people, according to the U.S. Centers for Disease Control and Prevention. The findings suggest industry self-regulation isn't doing enough to limit advertising to children, said Margo Wootan, nutrition policy director at the Center for Science in the Public Interest.

 "It's great that a number of food and media companies have stepped up and agreed to self-regulate," says Wootan, "but as currently practiced, the self-regulatory system is weak and ineffective."

SpongeBob SquarePants TV characters such as Nickelodeon's SpongeBob SquarePants and movies such as 20th Century Fox Film Corp.'s "Ice Age: Dawn of the Dinosaurs" were used extensively in advertising to promote kids meals, frozen desserts, and candy, the report said.

Meanwhile, Nestle, the world's largest food company, said in a statement that the company doesn't advertise to children younger than 6 and promotes only products that meet nutritional criteria to those ages 6 to 11.

Nestle participates in the Children's Food and Beverage Advertising Initiative, a voluntary self-regulation program.