The causes of obesity are everywhere. Societal factors play a big role: the lack of safe places to play, walk or bike; sedentary jobs; less time devoted to cooking and more eating out; bigger portion sizes in packaged and prepared food; and incessant marketing of junk foods that are high in calories. Sugar-sweetened drinks accounted for at least 20 percent of the increases in weight in the United States between 1977 and 2007, according to one study cited by the institute.

The institute’s report suggests a number of remedies that it believes have been proved to work. In Somerville, Mass., where some 40 percent of the younger elementary school children were overweight, there was a communitywide effort to offer healthier lunches in schools and restaurants, encourage walking and other physical activity, and change the small city’s culture. Children there gained less weight than their peers in other communities…

The institute says that a major cut in obesity rates will require multiple strategies on a population-wide scale. This will be even more challenging than the fight against smoking. But there isn’t any choice if we want to protect the public’s health, the strength of the economy and the government budget.