The nation's largest food and beverage companies are under renewed attack for what critics see as misleading ads for obesity-promoting foods, especially ads aimed at kids.

"The trickery that we're trying to stop includes General Mills' false claims that some of its corn-syrup- drenched products are 'natural,' and Coca-Cola Company's deceptive health claims about its Vitaminwater (which would be better called Sugarwater)," the Center for Science in the Public Interest said Wednesday in a release launching its "Stop the Lying Labels" campaign.

Industry representatives counter that they have worked to make their products healthier - just as critics have demanded.

"Since 2002, we have introduced more than 20,000 new product choices with fewer calories, reduced fat, sodium and sugar, and more whole grains," the Grocery Manufacturers Association said in an e-mail. "We have voluntarily adopted strict advertising criteria" through the Children's Food and Beverage Advertising Initiative.

That initiative, joined by General Mills, Burger King, Kellogg's, and 14 other industry heavyweights, says it is "designed to shift the mix of foods advertised to children under 12 to encourage healthier dietary choices."

But a new study funded by the Robert Wood Johnson Foundation in Princeton concluded that self-policing has failed because the industry's self-defined healthier foods "are not necessarily good for you."

The study, in the current Journal of Health Communication, analyzed food ads on 158 Spanish TV children's programs aired in the United States, and 139 English-language shows for kids. Among companies pledging to pitch healthier grub, 78 percent of the Spanish TV ads and 69 percent of the English TV ads were for fast food, sodas, snacks, and other foods that government nutrition experts deem high-calorie and low- nutrition. (When ads by companies not in the initiative were included, 84 percent in Spanish and 75 percent in English were for junky foods.)

Lead author Dale Kunkel, a communications professor at the University of Arizona, believes unhealthy food ads on Spanish kiddie TV is contributing to the heft of Hispanic children in this country, who are even heavier than their white peers.

Children younger than 9 "don't even understand the persuasive nature of advertising," Kunkel said. "They see it as information. The ads lead them to think it's normal to eat foods like that every day."

Another crusade launched last week by a Boston-based consumer group, Corporate Accountability International, is taking aim at McDonald's.

The group's social-media- based campaign, called MomsNotLovinIt, faults McDonald's in a news release for "ramping up marketing of 'healthier' options like oatmeal with the sugar content of a Snickers bar and salads that actually rival burgers and fries for calories."

In 2011, McDonald's responded to parental and consumer pressure by adding apples to Happy Meals, launching a mobile-phone app with nutrition information, and promising to gradually reduce sugars, saturated fats, and calories.

Contact Marie McCullough

at 215-854-2720 or mmccullough@phillynews.com.