Sugar. (Deb Lindsey/For The Washington Post)

APPARENTLY WE haven’t moved.

The latest results from the National Health and Nutrition Examination Survey, an authoritative federal source, is that the country’s obesity rate hasn’t budged over the course of this decade, despite unprecedented attention and public health campaigns devoted to the issue. The rate stood at nearly 35 percent in 2011 and 2012. The latest figures, for 2013 and 2014, peg the rate at nearly 38 percent. The 3-percentage-point increase from the previous results is not statistically significant — but the 6-point increase from 2003 and 2004 is.

Obesity-related heart disease and diabetes are among the most common American afflictions, and in many cases the misery is wholly preventable. Relatively small decreases in the projected obesity rate over the next couple of decades could produce billions of dollars in savings on treatment, too. Any rational government would respond strongly.

But how? First lady Michelle Obama has pushed hard to encourage better habits. Official dietary guidelines have improved, and various places are experimenting with calorie disclosures on menus. There’s a movement to require listing the amount of added sugar on packaged food labels. Education and transparency can’t hurt, particularly for those trying to eat healthier. Some Americans, particularly the wealthier and better-educated, have improved their diets over the past several years. Yet the message apparently hasn’t permeated poor and minority communities, where obesity rates still run astonishingly high, according to the new figures.

Some suggest cutting agricultural industry supports, which is a good starting point, because it is worth doing regardless of its impact on the country’s waistline. Efforts to undermine the improvements in school lunches also must end.

Others suggest that a powerful way to encourage behavioral change is to cut demand for the foods driving obesity rates. For example, many experts propose taxing sugary drinks, a major source of empty calories. Mexico, which has high per capita soft drink consumption and a high obesity rate, imposed a peso-per-liter soda tax in 2013, and initial indications suggest it has significantly cut soda consumption, particularly among the poor.

Yet soda taxes might also encourage people to turn to other sources for their sugar fix. So another option is to tax the ingredient itself, eliminating any substitution effects. This would be best done nationally rather than creating easily avoidable local sugar taxes. Sixteen percent of Americans’ caloric intake comes in the form of added sugars. New Food and Drug Administration guidelines recommend a maximum limit of 10 percent per day — about 50 grams — while the World Health Organization recommends half that.

Sugar taxes are not about punishment or blame but are about nudging people from destructive behavior in a way that’s both economically efficient and less coercive than many alternatives — New York’s ban on large soda cups, for example. Moreover, the government subsidizes the health costs that result from sugar overconsumption; it has good reason to recoup some of the money it wastes treating preventable illnesses.

Not every solution can or should come from government, of course. It’s in the interest of health insurers and employers to step up, too. But public health is a basic responsibility of government, and there’s no doubt that obesity is a public health crisis.