It is a complicated thing.
There may be an economic cure for the nation’s obesity: Hike the price of food.
Raising the price of a calorie for home consumption by 10 percent might lower the percentage of body fat in youths about 8 or 9 percent, according to new research from the National Bureau of Economic Research.
“An increase in the price of a calorie regardless of its source would improve obesity outcomes,” according to a working paper that three researchers prepared for the private, nonprofit bureau.
As the nation confronts an epidemic of flab, many experts have pointed a finger at low food prices as a cause, leading to proposals for taxes on sugary drinks, fast-food and junk food, as well as reductions in government farm subsidies.
The new research, which focused on youths, reinforces the idea that prices affect obesity and that raising fast-food prices would help, although pushing up the prices of healthy foods, such as fruits and vegetables, might hurt.
To conduct the study, researchers used measures of body fat from the National Health and Nutrition Examination Survey, a program of the Centers for Disease Control and Prevention, and the prices of 21 grocery items, including a pound of Jimmy Dean sausage, a 24-ounce loaf of white bread and a two-liter bottle of Coke.
They also looked at prices for three fast-food items: a Quarter Pounder with cheese from McDonald’s, a thin-crusted cheese pizza from Pizza Hut or Pizza Inn, and fried chicken from KFC or Church’s.
The research showed that people from different groups — males and females, whites and nonwhites — react differently to increased food prices.
Raising the prices of fast-food meals, for example, reduces the body fat of males more than of females. On the other hand, prices of fruits and vegetables have a greater influence on females, who tend to gain weight when those prices rise, presumably because of a resulting change in diet.
“The price of fruits and vegetables never has a significant effect on male percentage of body fat,” wrote the authors, Michael Grossman, director of bureau’s health economics program; Erdal Tekin, a Georgia State University economist; and Roy Wada, a health policy researcher at the University of Illinois at Chicago.
The study also found that the percentage of body fat for whites is more responsive to the price of fruits and vegetables than that of nonwhites.
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.