"When the International Food Information Council asked people how many calories they needed per day to maintain their weight, only 12 percent of respondents were able to give the correct answer," Weiss said. "That shows that people do not understand the context of calories in their diet and lifestyle."

According to Weiss, what consumers really want is choice.

"This is not a charity, it is a business," she said. "Restaurants are providing foods that their customers want and are going to eat." For some of today's customers, that now means healthier foods, Weiss said, and "if people didn't want them and they weren't selling, they wouldn't stay on the menu."

Weiss said her association supports recent moves in New York City, Seattle and elsewhere to limit trans fat cooking oils in restaurant fare. But she worries that deadlines for the changeover are being set too tightly to allow businesses to find reliable substitutes in time.

Grotto, author of the forthcoming book 101 Foods That Can Change Your Life, cautioned that McDonald's, Wendy's and other fast-food retailers haven't turned into health food havens quite yet.

"The bread-and-butter of the quick-service industry is not healthy foods," he said. "It's still very much driven by what the consumer wants," and for most consumers, that's high-calorie, fatty fare, he said.

So, what efforts can work to change people's dining preferences for the better?

"I'm old school on this," Grotto said. "I think that starts in the home." When parents model good nutrition and exercise, healthier kids will follow, he said, and those children typically grow into health-conscious adults.

"If we are ever to tackle this huge problem of obesity, it's not about any one smoking gun," Grotto said. "Everybody has got to play a role in turning this around."

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