"It becomes a marketing thing, a fashion thing," says Lynch. "You want to buy the food with the cartoons on the box or the toy."

The industry should have done more to direct the child obesity debate, agrees Pepsi's Leach. Much of the focus has been on getting junk food out of school vending machines, but Leach argues that's just a tiny part of the solution.

He says food companies ¡ª including his own, one of the biggest losers in the vending machine fight ¡ª should have offered healthier vending options long ago, then redirected attention to other critical issues, such as getting physical education back in schools.

Science lag

In many ways the food industry is chasing a moving target. For years, food production was a better understood science than nutrition. And so whole grains were abandoned and hydrogenated fats embraced.

The medical community takes much of the blame, says Dr. George Blackburn of Harvard Medical School's nutrition division.

"We didn't even put nutrition in the medical curriculum except in the last 30 or 40 years," he says. "As soon as we got drugs, to hell with nutrition. We're just now getting it to be a professional responsibility to be sensitive to people's healthy eating."

Today, the food industry suffers from nutrition research overload, with tidal waves of new and sometimes contradictory health findings that strain its ability to produce appealing foods that are in sync with the latest science.

Even when companies succeed, they still are susceptible to scientific surprises that can break a business.

When saturated fat was the enemy, companies reformulated their products, says Grocery Manufacturers Association spokeswoman Stephanie Childs. Only later did they learn that the trans fats they had replaced them with were even worse.

But the science lag can't explain the growing ubiquity of food or the ballooning portions of it, from bigger buckets of movie popcorn to McDonald's much vilified ¡ª and now defunct ¡ª Supersized burgers.

The industry again points to the consumer, saying that starting in the 1970s people demanded convenience and bargains. Smart companies launched family sizes and sold food everywhere from office supply chains to hardware stores.

"It's a tremendous way of getting people to buy more at lower cost to the producer," says Nestle, who notes research has shown that the more food people have, the more they eat. "There's no question that that's an incentive to buy. Everybody loves a bargain."

This has changed how Americans eat. So-called portion distortion has contributed enormously to obesity.

And overeating becomes even easier when food is everywhere, Nestle says. Meal time is all the time when everything from cars to backpacks to grocery carts are redesigned with snack food holders to accommodate constant munching.

But Nestle acknowledges it becomes a chicken-or-egg question. Lifestyles have changed and Americans want to eat big and on the run. Did that lead food companies to change, or did new products change Americans?

Engineering obesity?

Despite his criticism of the industry's practices, Yale's Katz acknowledges companies are in a difficult position. Ultimately, they sell food, and staying in business means selling the foods people want. Public health is secondary.

But what if those companies engineered their foods to make you eat more of them? Though he acknowledges that evidence is scarce, Katz believes companies do just that, much the way tobacco companies were accused of tinkering with nicotine.

Research shows that people eat more when faced with a variety of foods, or even a variety of flavors within a single food. For example, you are less likely to overeat plain baked potatoes than those drenched in butter, salt, sour cream and chives.

Sugary cereals, Katz notes, have more salt in them than many potato and corn chips. Katz believes that's one way to make a cereal's flavor more complex and appealing to get people to eat more of it.

Industry officials dispute Katz's theory. Earl, of the Food Products Association, says he knows of no company that has knowingly manipulated ingredients as Katz suggests.

Whatever the food industry's share of the blame, Tillotson, the Tufts professor, thinks obesity lawsuits are inappropriate and Congress is considering a measure to bar them. Food companies were asked to feed a hungry nation; suing now penalizes them for doing so, he believes.

Industry officials contend lawsuits divert resources from efforts to educate consumers and to produce healthier foods. Market demand and a sense of social responsibility are better catalysts for change, they say.

And some companies deserve real credit for living up to that.

* General Mills Inc., the nation's No. 2 cereal maker, now makes all its cereals from whole-grain flour.

* Kraft Foods Inc., the nation's biggest food manufacturer, says it's curbing snack food ads to children and will redesign packaging to flag its healthier products. The company also recently cut the fat in hundreds of products and stopped marketing snacks at schools.

* PepsiCo Inc., which credits healthier products with two-thirds of its revenue growth, has launched various healthy eating education efforts and even has tied executive bonus programs to the development and marketing of healthier items.

* The Coca-Cola Co. now labels some of its sodas with nutrition data for the entire bottle, not just one serving.

But while critics applaud the changes, they say industry goodwill and consumer demand aren't reliable enough. The realities of competition can push goodwill aside and consumers can't be counted on to want what's good for them.

Leach acknowledges it's true that industry will follow consumer demand, and that includes high-fat, high-sugar foods.

That's why Richard Daynard, director of the obesity and law project at Northeastern University School of Law in Boston, says lawsuits ¡ª some are pending, some were dismissed or settled ¡ª still are needed as part of a larger assessment of the obesity epidemic.

"You can't get to a solution until you get a diagnosis. If you don't see the role of the junk food industry in causing the problem and in continuing to maintain the problem, you've missed a big part of the diagnosis," says Daynard, who is leading a soda industry lawsuit.

"Things that dramatically assign blame, like a lawsuit, help people make a diagnosis."

Ellen Van Gelder, an obese 41-year-old health care worker from Concord, N.H., doesn't need a lawsuit to make her diagnosis.

Though she disapproves of many of the food industry's marketing methods and wishes food companies would make it easier to eat healthier, ultimate responsibility for her weight is her own, she says.

"I would love to blame somebody else. The reality is it's each person's responsibility," says Van Gelder, who has battled her weight her entire life. "You put the food on your plate. You choose whether to eat it."