Barry Popkin is the director of the Interdisciplinary Obesity Program at the University of North Carolina at Chapel Hill and author of The World Is Fat. Popkin recently coauthored a study that detailed the results of the 20-year-long Coronary Artery Risk Development in Young Adults (CARDIA) project, which measured the correlation between fast food prices and Americans’ health.

The study, completed between 1985 and 2005, found that, among other things, when prices of fast foods and sugar-sweetened beverages went up 10 percent, participants consumed 56 less calories per day on average.

Popkin recently sat down with QSR’s Sam Oches to discuss the study; below are excerpts from the interview. For more on Popkin’s study, be sure to check out QSR’s June print issue, and stay tuned at QSRmagazine.com for exclusive video of the interview.

Why did you do this study and what were the results?

We have an explosion of people consuming too many calories in the U.S. and across the globe. We have an explosion of overweight and obesity across the globe. And we’re very concerned about it. My research program and the center I lead at the University of North Carolina is all about obesity. I’m concerned with finding ways to prevent obesity. One of the options we have is to consider price changes in one way or another.

The major hypothesis is we have lots of studies across the globe that show us, when you drink a beverage, be it water or Pepsi or beer, you don’t reduce your food intake. There are biological and other reasons for it, but essentially our drinking and our eating are separate events, and what we drink doesn’t affect what we eat very much. We don’t reduce our calories. Okay, we know that. We’ve done studies, other people have done studies to show that sugar-sweetened-beverage intake, as it goes up, increases your risk of overweight, increases your caloric intake. As it goes down, you reduce it. … But we wanted to ask a bigger question: If the price changed for the sugar-sweetened beverages you consume, if it went up or down, did you adjust your intake? In turn, if you adjusted your intake of sugar-sweetened beverages, what did it do to the other food you consumed and drank? Did you just switch from Pepsi to Mountain Dew, or did you cut your calories and maybe drink less Pepsi? In turn, what did that do to your total caloric intake, and in turn, what did that do to your weight and your risk of diabetes?

Essentially, what we found is that if we raise the prices, let’s say by $1, for a two-liter bottle of soft drink … we would reduce by 124 calories a day the total consumption of all foods and beverages in caloric terms for the average adult.

Now that health care has passed and Michelle Obama has her Let’s Move campaign, do you see the taxes on sugar-sweetened beverages being passed as part of this wave?

At one point, there was a 1 percent tax on soft drinks per ounce in both the Senate and the House to help raise money. They’ll be voting very soon in Philadelphia, and New York is voting on a 1 cent per ounce tax on sugar-sweetened beverages, and there’s a reasonable chance it looks like now it might pass. (Editor’s Note: The New York proposal did not pass.) There are several other states talking about this, giving part of the money to public health, and part of it as a revenue raiser.

The new health care legislation requires [nutrition] labeling in all [quick-service] stores … We don’t really know how the labeling will work. We know it won’t hurt; we know it’s not going to hurt the business of the quick serves, but we think it’s going to shift them. They’re going to be creating healthier portion sizes and slowly, they’ll be the people that always consume. But there’s a general shift that’s going on with some of the consumables within [the quick-service] sector. And labeling will make a difference. How big a difference? I don’t think it’s enough. I think it will help. There’s just a lot of things that have to happen.

Don’t you think that some responsibility for obesity lies with the consumer?

That’s an interesting question. If you’re an American where you think everything is individual behavior, you look at the world that way. However, in the same time that Americans increased by 200–300 calories a day, how much they consumed over the last 20 years, everybody in the globe did the same. You think they’re all lazy and gluttonous? A lot of them are poor people, or illiterate, and so on, and their environment changed. I can take you to this village in Mexico that had no roads 20 years ago, and five years after they got roads there were little tiendas everywhere selling all of the soft drinks in the world, and they exploded in weight and risk of diabetes.

There are six countries today with two thirds of adults overweight: the U.K., Australia, and the U.S., Mexico, Egypt, South Africa. There are over 25 countries now with over half the adults overweight. Half of them are countries you would have though of as low in income and third-world a decade or two ago. Everybody’s changed, the environment, the technology, the marketing, the availability of food and drink.

In the last 20 to 30 years, we’ve gone up by 219 calories a day with the average U.S. adult consumes in sugar-sweetened beverages. Just between 1987-88 and 1996, the average American added 21 ounces of beverage to their diet. All of that was sugar-sweetened beverages. Were we thirstier? Were we more active and more thirsty in those 20 years? Water didn’t change during those 10 years, water intake was the same. It’s just we added sugar sweetened beverages. Marketing, availability, pricing, has done it.