The new industry standards could protect soda manufacturers from childhood obesity-related lawsuits, although some litigation is almost certain to go forward.

The association is urging bottling and soda companies to sell more bottled water, sports drinks and 100 percent fruit juices.

Appropriate Food Environment

The policies come after years of criticism from trial lawyers and public health advocates that easy access to soda in school vending machines has contributed to the nation's rising childhood obesity rate.

About 16 percent of American children, ages 6 to 19, are overweight, according to the latest data from the Centers for Disease Control and Prevention (CDC).

"We are responding to what parents have said is an appropriate food environment for younger children while they are in school," said Susan Neely, president and chief executive for the Washington trade group.

The new guidelines were approved unanimously by the group's board of directors, which includes 20 bottling companies that comprise 85 percent of the beverage school vending market, Ms. Neely said. Coca-Cola and Pepsi officials said they support the move.

Soft-drink manufacturers may prosper from the rules by marketing more of their alternative brands instead of cola, which has lagged in sales in the past year, said Tom Pirko, president of Bevmark LLC, a Santa Barbara, Calif., food and beverage consulting firm.

Childhood Obesity-Related Lawsuits

The industry standards could protect soda manufacturers from childhood obesity-related lawsuits, said Louise Ellingsworth, a class-action lawyer with St. Louis law firm Bryan Cave LLP.

"Certainly going forward there could be some retroactive cases on this matter, but then the plaintiffs are only getting monetary relief. They would not be changing the industry because the industry has already changed," she said.

George Washington University law professor John Banzhaf III, who for the past few years has led the trial lawyers group filing obesity lawsuits, said the new policies will delay a lawsuit his team was planning to file.

Mr. Banzhaf would not name potential defendants, but said the suit addressed the school soda contracts, which he called "Coke for kickbacks in schools."

"It may be delayed and redrafted at this point, but I doubt we will abandon it," he said, adding that the guidelines do not protect school boards or soda companies from litigation.

Moderation and Physical Activity

The Center for Science in the Public Interest, a Washington health advocacy group that has worked with Mr. Banzhaf, said the industry rules do not go far enough.

"It's a good step for elementary schools, but it basically does nothing to address the high schools," said Margo Wootan, nutrition policy director.

Under the guidelines, high school vending machines can sell regular and diet soda in only half of the machines' slots. The remaining half must be filled with drinks such as bottled water, fruit juices and sports drinks.

Washington dietitian Lalita Kaul said moderation and physical activity will need to coincide with the modified vending machines to reduce obesity rates.

"Children need to learn to consume these drinks within reason," she said, noting that sports drinks and 100 percent juices can be high in calories and sugar.