Boston ? I work in a danger zone. Across the street from my office is a restaurant that sells bagels larger than my hand. Around the corner is a Ben and Jerry’s that scoops an ice cream flavor that is “Phish food” for the whale-sized. This morning the local pizza place put up a sign announcing “all you can eat” night.

Life on this Boulevard of Broken Diets is not easy. After all, like most Americans I subscribe to the “just say no” school of weight control. This is a school that promotes theorists like Will and Power. It offers a school motto of Personal Responsibility.

Even as the ideal body has gotten slimmer and the real body has gotten wider, students of this philosophy react like our Puritan ancestors. We assume that what separates the saved from the damned is virtue.

Well, fat chance for virtue. The only part of our economy that seems to be expanding is the waistline. Sixty percent of Americans are overweight. Twice as many kids are overweight as a generation ago. And in the last few weeks we’ve had health warnings about fat that range from diabetes to Alzheimer’s.

The only good news is that we are beginning to shift from describing obesity as a moral failing to describing it as a public health epidemic. We are beginning to shift at least some attention from self-control to environment-out-of-control.

This change is partly due to the collective, um, weight of scientific studies. Yale’s Kelly Brownell, who coined the phrase “toxic environment,” sums them up this way: “When the environment changes, weight changes.” When, for example, immigrants from thinner countries come to America they gain weight while their cousins back home stay lean. When you give moviegoers a big box of popcorn instead of a small one, they eat about 50 percent more.

The change also comes from the discovery that there really were business plans for the fattening of America. We don’t actually have much less willpower than we used to. In “Fat Land,” Greg Critser details the deliberate supersizing of servings from the Big Mac to the Big Gulp. Instead of expanding the number of customers, they expanded the existing customers.

At the same time, we have learned something from the campaigns against smoking. Yes, it’s up to the smoker to stub out the last Marlboro. But personal responsibility is not a free pass for corporate irresponsibility. It’s easier to just say no when you aren’t being manipulated and marketed to say yes.

It’s not an accident that Kraft, maker of Oreo cookies and macaroni and cheese, became the first Big Foodie to pledge to help the fight against obesity. The company is, after all, a subsidiary of the much-sued Philip Morris before it changed its name and image to Altria.

As Margo Wootan of the Center for Science in the Public Interest says, “Kraft belongs to a tobacco company that knows what the inside of a courtroom looks like.” It didn’t take a Ph.D., she adds, to realize that everyone would figure out that cookies and cheese contribute to obesity.

One of Kraft’s pledges is to stop marketing in schools. Indeed, the public seems most willing to acknowledge the weight of the environment in the weight of kids.

The first step in downsizing Americans may be in the schools. Over the past decade, schools have said yes to soft drinks and junk food in hallway vending machines. Now some large school districts from Los Angeles to New York have banned the sale of sodas.

But it’s likely to be a long haul to get smaller portions, labeling in fast-food restaurants and to slim down advertising to kids. Wootan says, “People still haven’t made the connection about how industry practices shape and influence their choices. Your child begs you for junk food, begs you to go to McDonald’s and you think ‘that’s kids.’ You don’t think, ‘shame on that food company.”‘

Food is one part of a complex obesity problem that includes Game Boys instead of ball games and TV instead of track. Moreover, it’s still tricky to attack fat as a health issue without attacking fat people, and we’ve had a big enough portion of that, thank you. But Brownell believes, “We are a place where it no longer makes sense to blame people for a problem their environment is causing.”

What do we need to change the environment? How about Will and Power?