(CNN) – More than 21-million children nationwide receive free or reduced lunch. Now, researchers are taking a closer look at what that means for their health.

A study by a Virginia Tech researcher shows there may be a link between kids who receive free or reduced lunch and obesity.

Dr. Wen You, Associate Professor at Virginia Tech, says, “The group of kids who were from low income families and chose to participate in both school meals and school breakfast and school lunch programs. They are the most vulnerable group.”

Nationally, 1,000 schools have been studied and more than 20,000 children have had their weight monitored.

Dr. You says, “The weight change over the years can be more comfortably kind of linked potentially to the program participation”

If kids eat breakfast, then the rationale is then they will eat less during lunch. But Dr. You says her findings suggest that the findings were similar for kids who eat breakfast and those who eat breakfast and lunch. “What we are trying to look at is to see those students who simultaneously participated in both programs we would hope to see that fat will either smaller or go away but we found it’s actually bigger.”

Dr. You says the next step is taking a look at nutrition quality, and the number of nutrients kids are actually eating.

According to the National School Lunch Program, students who receive free lunch are from families whose income is no more than 130-percent of the federal poverty level. For reduced lunch, that number is 185-percent.Copyright 2016 CNN