In recent years, such research has spurred an array of proposals to make food — or at least some foods, such as those with high sugar or fat content — more expensive. But the most direct means, economists say, is to tax calories.

Abigail Okrent, an Agriculture Department researcher, and Julian Alston, a professor at the University of California at Davis, have compared various options: a fat tax, a sugar tax, a calorie tax and a general food tax.

“A calorie tax would get you the biggest bang for the buck; it’s the most direct way of taxing obesity,” Okrent said.

There are at least a couple of problems with that option, though. Nutritionists would prefer to distinguish between “good” and “bad” calories, and taxing calories might push the price of staples beyond the reach of the destitute.

“It’s probably not politically feasible,” she said.