It’s tempting to blame big food companies for America’s big obesity problem.

After all, they’re the folks who Supersized our fries, family-portioned our potato chips and Big Gulped our sodas. There’s also the billions they’ve spent keeping their products ever on our minds and in our mouths.

Likened by some to the way tobacco companies seduced smokers, such practices have made the food industry the target of lawsuits and legislation seeking to yank junk food from schools and curb advertising to children.

But some experts say neither the problem nor the solution is nearly so simple.

“You don’t have the collusion or the cover-up you had in smoking,” says James Tillotson, a business and food policy professor at Tufts’ Friedman School of Nutrition. “We want to blame somebody, but the thing is, we’re all a part of it.”

Sure, companies set the stage with cheap, calorie-dense foods.

But government also has propped up agribusiness, the medical community was slow to take on obesity and good nutrition, and consumers seem determined to move less and eat more, says Tillotson, a former food industry executive.

How much of that burden of blame belongs to the food industry can be difficult to answer.

Personal responsibility

The food industry emerged at a time when malnutrition was the nation’s chief dietary concern. But at some point food became too plentiful, a change that altered the culture of the American diet.

Yale obesity expert Dr. David Katz says that’s because companies aggressively peddle food to people who don’t need it.

Food industry officials prefer to call it consumer choice.

“We don’t think the food industry has done anything particularly wrong in this regard,” says Robert Earl of the Food Products Assn., a lobbying group that prefers to indict sedentary lifestyles and poor choices.

Companies have tried to help people make better choices, he says, offering healthier products and more nutrition data. But people can’t be forced to make the right choice and consumer disinterest doomed many of those products.

He’s right. Consumers bear much responsibility for their weight and the fact that two-thirds of Americans are overweight or obese. It’s not the industry’s fault that people don’t get exercise, or that schools have cut physical education, or that people prefer the taste of Twinkies (500 million sold a year) to tofu (much less).

But critics call Earl’s assessment disingenuous. Personal responsibility has limits in the face of a multibillion-dollar marketing whirlwind pushing countless high-calorie treats.

“They (food companies) are putting $36 billion into directing those choices,” says Marion Nestle, a nutrition professor at New York University and critic of the food industry. “And their methods are very effective.”

Personal responsibility also falters when it comes to children, who are bombarded by junk food ads that undermine parents.

Everything from child-friendly merchandizing of sugary cereals to cartoon ads is designed to give companies more sway over what children eat, says Dr. Susan Lynch, a child obesity doctor and wife of New Hampshire Gov. John Lynch.

Such tactics make it tougher to teach good eating habits to kids who equate food with entertainment, she said.

“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.”

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.

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 Assn. 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 – and now defunct – Supersized offerings.

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.

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.