We’ve got a growing problem in the US: almost 35 percent of American adults are obese.

Dr. Dariush Mozaffarian, dean of the Tufts Friedman School of Nutrition Science and Policy, and Dr. Bruce Lee, director of the Global Obesity Prevention Center at Johns Hopkins, think that these stats constitute a national emergency.

According to Mozaffarian, the high obesity rates stem more from poor diet than lack of exercise. Americans increasingly eat liquid calories, starch, and sugar.

An added problem? Scientists are still learning what constitutes healthy food. Two decades ago, we blamed fat for most weight gain. Now, that blame has shifted to calories -- which Mozaffarian sees as equally ill-advised.

“For short-term … cut your calories, you’ll lose weight,” he says. “But at the end of the day, our bodies have a beautiful and intricate and powerful set of mechanisms to help us regulate our weight … What we’re starting to understand now, in the science, is that there are certain foods that help those beautiful mechanisms and help us maintain our weight and that there are certain types of foods that don’t.”

This means that it’s better to drink whole milk than chocolate skim milk, even though the latter has fewer calories.

Lee believes that policy intervention is key to changing our country’s eating habits.

“We shouldn’t keep thinking of the individual and say, ‘okay, they’re going to take care of it’,” Lee said. “There needs to be more action from all different sectors of society.”

What kinds of policies might work?

“Let’s tax almost every packaged food in the food supply and use that 10 percent tax, let’s say, to heavily subsidize nuts, fruits, vegetables, yogurt, beans … so that a serving of fish in a restaurant is not the most expensive thing on the menu, it’s the cheapest thing on the menu,” Mozaffarian says.

Lee underscores how crucial it is that we actively combat obesity and its causes.

“People are actually dying, getting sick, and there needs to be more urgency,” Lee says.