The USDA's Economic Research Service (ERS) findings are based on an examination of the diets and weight of around 7,000 children between kindergarten and third grade.
"Children who lived in metropolitan areas where fruits and vegetables were relatively expensive gained significantly more weight than children who lived where fruit and vegetables were cheaper," said the USDA, adding that the children who participated in the study had a similar way and standard of living.
On average, the children gained three pounds more in weight during the period than the standard established by the Center for Disease Control.
Those who lived in the region with the highest priced fruit and vegetables- around double the cost of the lowest-priced region- gained about 0.21 BMI units more excess weight than similar children nationally, according to the study.
On the other hand, children living in the region where the products were the lowest-priced gained 0.28 BMI units less of excess weight than other children.
The research was based on families who had the same incomes but "faced different food prices or availability." The results were adjusted for other individual factors such as birthweight, sex, race and physical activity.
The findings also reveal that "one behavioral factor that was as strongly associated with weight gain as fruit and vegetable prices was time spent watching TV. Children who watched 2 to 3 hours per day more television on average than the national average gained 50 percent excess weight, as measured by the BMI."
The USDA stressed that its study could not confirm the link between higher prices and the purchase of fresh produce.
"However, the findings suggest the need for more research to determine the impact prices may have on the consumption of fruits and vegetables by children," it said.
Indeed, fruit and vegetables are also linked to health in a number of other ways. A recent study carried out in Canada found that fruit and vegetable consumption, independent of calcium intake, is associated with stronger bones in teenage boys.
It follows a study reported in 2004 by researchers in Northern Ireland showing that 12-year-old girls with a high fruit consumption had significantly higher heel bone mineral density than moderate fruit consumers.
And recent research by scientists at the University of California shows that including plenty of fruit and vegetables in the diet could halve chances of developing pancreatic cancer, supporting findings published in the May issue of the International Journal of Cancer.
The Dietary Guidelines for Americans, published in January 2005, recommend that Americans consume two cups of fruit and two and a half cups of vegetables per day, for a reference 2000 calorie per day diet. They also advise balancing intake of each of five groups (dark green, orange, legumes, starchy and other vegetables) over the course of the week.