UW researchers Dr. Adam Drewnowski, director of the Center for Public Health Nutrition, and Dr. Pablo Monsivais, a research fellow in the center, studied food prices at grocery stores around the Seattle area in 2004. They found that the foods which are less energy-dense -- generally fresh fruits and vegetables -- are much more expensive per calorie than energy-dense foods -- such as those high in refined grains, added sugars, and added fats.
When the researchers surveyed prices again in 2006, the found that the disparity in food prices only worsened with time. Lower-calorie foods jumped in price by about 19.5 percent in that two-year period, while the prices of very calorie-rich foods stayed stable or even dropped slightly, the researchers found. The general rate of food price inflation in the United States was about 5 percent during that period, according to the U.S. Department of Labor.
"That the cost of healthful foods is outpacing inflation is a major problem," said Drewnowski. "The gap between what we say people should eat and what they can afford is becoming unacceptably wide. If grains, sugars and fats are the only affordable foods left, how are we to handle the obesity epidemic?"
Research conducted by Drewnowski and others at the UW Center for Obesity Research had previously shown that per calorie food costs were much higher for fresh produce and other recommended foods than for fats and sweets. Those studies were based on prevailing food prices in the United States and in Europe.
This project was the first of its kind to track the change in prices over time not by food group, but by food quality. The Labor Department monitors food prices by tracking the cost of an average "food basket," which is calculated based on what American consumers purchase at the grocery store. However, the researchers argue, the inflation rate of the overall basket may drastically underestimate the rising cost of the healthiest foods.
The UW study looked at price inflation in foods grouped by energy density, or calories per gram of food. Energy density is one measure of food quality, since many energy-dense foods also tend to be low in nutrients. People who eat energy-dense foods may consume more calories than they need.
"We are an overfed but undernourished nation," said Drewnowski.
Drewnowski and Monsivais argue that the study provides yet another piece of evidence that obesity isn't just a personal problem -- it's an economic one.
"We need to focus on bigger-scale changes, like the farm bill or other policy measures that can address the disparity in food costs," Monsivais said.
The project was supported by the U.S. Department of Agriculture and the National Institute of Dental and Craniofacial Research in the National Institutes of Health.