PHILADELPHIA — Overweight children are absent from school on average 20 percent more often than their normal-weight peers, according to a new study conducted by researchers at the University of Pennsylvania and Temple University.

The study of more than 1,000 fourth-, fifth- and sixth-graders in the Philadelphia school system also showed that body mass index is as significant a factor in determining absenteeism from school as age, race, socioeconomic status and gender.

“What's keeping them from school, more than health issues, is the stigma and the bullying that accompanies being overweight,” says Andrew Geier, a doctoral candidate at Pennsylvania and one of the researchers of the study. “Future research should explore this additional, very damaging side effect of being overweight.”