There is no question that kids perform better in school after having a nutritious breakfast. But a recent study found that weight gain and obesity were unintended consequences for some Philadelphia children when the School Breakfast Program was offered in the classroom rather than in the cafeteria before school.

Researchers from the University of Michigan School of Public Health and Temple University’s Center for Obesity Research and Education followed more than 1,300 students in grades 4 through 6 from low-income communities at 16 Philadelphia public schools for about 2½ years. They partnered with the Food Trust and the School District of Philadelphia for the study.

The results were published Monday in JAMA Pediatrics.

Nationally, about 12.2 million children from low-income households take part in the federally assisted School Breakfast Program.

About half the schools in the study offered students breakfast in the cafeteria before classes began, along with a standard nutrition education program. The intervention schools served breakfast during first period along with breakfast-specific nutrition education.

The researcher’s initial hypothesis was that the intervention program would help decrease the prevalence of obesity and overweight in those students. Past studies showed that children who ate a regular breakfast were more likely to be at a healthy weight, said lead author Kate Bauer, an assistant professor of nutritional sciences at the University of Michigan School of Public Health.

All the breakfasts met U.S. Department of Agriculture requirements with a fruit or fruit juice, a grain, a protein, or milk. The calories on average didn’t differ between the meals offered in the classroom or cafeteria. The study wasn’t a test of the breakfast program, it was a test of when and where the school breakfast was offered, said Bauer.

The Philadelphia children’s heights and weights were measured to determine their body mass index (BMI). At the beginning of the study, nearly 18 percent of the students were overweight (defined as BMI over the 85th percentile) and 21 percent were obese (defined as BMI at or over the 95th percentile).

At the schools that implemented the One Healthy Breakfast educational program, students received 18 nutrition education lessons about the importance of eating a good breakfast. Tags were placed on local corner store shelves near the schools with targeted messages, and the One Healthy Breakfast logo or mascot to help kids identify nutritious breakfast options.

Parents were also included in the education efforts through monthly newsletters about healthy food options, recipes and family activities. There were also displays at back-to-school night events and report card conference days.

At the end of the study, researchers found that about 12 percent of the schoolchildren who ate breakfast in the classroom and 4 percent who ate breakfast in the cafeteria had a BMI in the obesity range, said Bauer, an epidemiologist.

Researchers said that the reason for the weight increase was that some kids may have already eaten breakfast at home, and the older elementary and middle school students had the freedom to buy food on the way to school, adding extra calories to their daily intake.

“Many were having multiple breakfasts at multiple locations in the morning,” said Bauer.

In the end, the researchers concluded that more research was necessary, and that they needed to find ways to improve the participation rates in the school breakfast program without having an increase in obesity among the children participating.