Bullying and teasing, diabetes and asthma — the costs of childhood obesity are far-reaching.

Now for the first time, scientists have found that obesity is also keeping kids out of school.

“In addition to the medical and psychosocial consequences of obesity and excess weight, heavier children have greater risk for school absenteeism than normal-weight children,” said Temple University’s Gary Foster, Ph.D., in a study published in the August issue of the journal Obesity.

“And as the rate of childhood obesity increases, school absenteeism can be expected to increase.” Foster is a professor of medicine and public health and director of the Center for Obesity Research and Education.

The study focused on more than 1,000 fourth-, fifth- and sixth-graders from Philadelphia elementary schools. The researchers found that overweight children were absent significantly more than normal-weight children: 12 days vs. 10 days over the course of the school year. Weight ranges were determined using body mass index.

“Because every school day is crucial to students’ academic success, absenteeism hurts, especially those already struggling with school,” said Joan Nachmani, director of the Nutrition Education Program at the School District of Philadelphia and study co-author.

Nachmani fears that there’s also a subgroup of children who aren’t captured in these statistics: those who are homebound due to their obesity because they’re unable to walk to school, withstand the teasing from other students, or overcome the many health problems caused by obesity.

As with adults, excess weight among children and adolescents in the United States is a serious problem that continues to worsen.

In fact, since 1980, the number of overweight 6- to 11- and 12- to19-year-olds has tripled to 18.8 percent and 17.4 percent respectively, according to the Centers for Disease Control and Prevention. Among minorities, obesity disproportionately strikes Mexican-American and non-Hispanic black children.

Previous studies linked the rise in overweight children to increases in the medical problems associated with excess weight, such as type-2 diabetes, hypertension and metabolic syndrome. Overweight children also suffer psychologically and socially, from rejection and bullying by other kids as well as from behavior problems.

“For all these reasons, heavier children might be missing school. They might also stay home more often on days when they have physical education class because it’s harder for them to perform the physical activity,” Foster said.

Foster suggested that future studies look closer at the connection between obesity-related absenteeism and poor academic performance, as well as parent educational level and household income.

Experts are hopeful that schools can have a positive impact on reducing excess weight and obesity in children through healthier school lunches and physical activity programs. But as the current study shows, the kids who need it most might not be in school to benefit, he said.

This study was funded by the Centers for Disease Control and Prevention.

“The Relationship Between Relative Weight and School Attendance Among Elementary School Children” by Andrew B. Geier1, Gary D. Foster2, Leslie G. Womble2, Jackie McLaughlin1, Kelley E. Borradaile2, Joan Nachmani3, Sandy Sherman4, Shiriki Kumanyika1, and Justine Shults1, is published in the August issue of the journal Obesity (1University of Pennsylvania, 2Temple University, 3the School District of Philadelphia, 4the Food Trust).