OVER THE LAST three decades, the U.S. has become increasingly fat, unhappy - and sick. Expensively so.

At $147 billion a year, obesity-related illnesses - diabetes, heart disease, some forms of cancer and stroke - cost the nation's medical system almost twice as much as treating all forms of cancer, says Kathleen Sebelius, U.S. secretary of Health and Human Services. Obesity is the single biggest reason for the recent increase in health-care costs, maintains Eric Finkelstein, a health economist.

Two-thirds of American adults and 20 percent of American kids are overweight or obese - and the scales keep going up. Among adults, the rate of obesity doubled from 1980 to 2004. The rate of childhood obesity has tripled, with ominous side effects. Not so long ago, Type II diabetes was labeled "adult-onset" because only adults, most of them overweight, got it - and suffered the health problems that often afflict its victims: weakened hearts, lost limbs, blindness. Now, though, diabetes in juveniles is not necessarily "juvenile diabetes." Instead, kids are getting adult-onset diabetes in record numbers, seriously affecting their lives as well as their country.

Obesity is now an issue that can no longer be a matter of calorie-counters, "willpower" and stern lectures from doctors about getting more exercise.

It's why the Centers for Disease Control and Prevention last week convened "Weight of the Nation," its first conference on obesity. It's why the CDC's 24 recommendations to deal with obesity are focused on community and government action, recognizing obesity as the result not only of individual choices, but of recent negative changes in the social environment that have affected poor and minority communities disproportionately.

Obesity is directly linked to poverty, with the highest rates among low-income people in the black, Hispanic and Native American communities. They are more likely to live in areas without supermarkets, having to rely on convenience and "corner" stores that stock mostly processed food high in calories and low in nutrition. (Of course, even when supermarkets are close by, healthy produce and protein are priced so high that they're out of reach to many people trying to make it on food stamps.)

The same neighborhoods that are "food deserts" - devoid of grocery stores - are often at the same time "jungles" of fast-food outlets. Studies show that the higher the ratio of fast-food restaurants to groceries, the higher the obesity rates.

Among the CDC recommendations:

* Make public venues - schools, municipal buildings, prisons and juvenile-detention centers - examples of lifesaving nutrition, making healthy foods cheaper while restricting junk.

* Provide incentives for supermarkets to locate in underserved areas and for individuals and groups to buy food directly from local farms.

* Require schools to teach physical education, provide extracurricular activities for physical activity and improve infrastructure and access to safe places to walk and bicycle.

THE CDC's SUGGESTION that communities consider placing taxes on sugar-sweetened beverages has made headlines.

But its recommendations don't really address another problem: government agricultural subsidies for corn and soy have made them an almost inescapable - and fattening - part of our diets. They are found in nearly all processed foods as well as in animal feed, which means meat that, while cheaper, is higher in calories than it used to be.

Still, the CDC conference is a public recognition that obesity is everyone's problem, no matter what the numbers on your home scale.