When the prices of fruits and vegetables go up, the body fat in young children also rises, according to a recent study. 

"There is a small, but significant, association between the prices of fruit and vegetables and higher child [Body Mass Index] BMI," Taryn Morrissey, the study's lead author and assistant professor of public administration and policy at AU's School of Public Affairs, said in a statement.

Researchers from American University in D.C. found that when the prices of fruits and vegetables go up, low- and middle- income families may buy less of them and substitute cheaper food that may not be as healthy and have more calories. The association is small, but significant, since the BMI is an indicator of total body fat, which is related to the risk of life-threatening diseases.

For the study, investigators analyzed data from the Early Childhood Longitudinal Study-Birth Cohort, a nationally representative study of children from infancy to age 5, and linked it to local food price data from the Council for Community and Economic Research Cost-of-Living Index.

They found that children living in areas with higher-priced fruits and vegetables averaged higher measures of BMI scores compared with their peers in areas with lower-priced fruits and vegetables, researchers said in the study.

Researchers said that while, in general, food prices have trended downward in recent decades, particularly the prices of snacks and sugar-sweetened beverages, the prices of restaurant meals and fruits and vegetables have increased. Fruit and vegetable prices increased by 17 percent between 1997 and 2003 alone, researchers said in the study.

More than 26 percent of 2- to 5-year-old children nationwide were considered overweight, defined as having a BMI above the 85th percentile, in 2009 and 2010, up from 21 percent a decade earlier.