If we want to improve American kids' performance in math, it may behoove us to no longer consider cafeteria pizza a serving of vegetables.
According to a new study out from the University of Missouri-Columbia, kids who were persistently obese did worse on math tests than thinner children.
That's bad news for Missouri, which ranked 9th worst in the country for childhood obesity rates in 2010.
The study used data from the national Early Childhood Longitudinal Study-Kindergarten Cohort, which followed 6,250 kids from kindergarten to fifth grade. Students who participated in the survey took math tests, were weighed and measured, and their parents and teachers answered questions about their emotional and social well-being.
The effect was most pronounced in students that were overweight from kindergarten through fifth grade, as compared to kids who were never obese. Boys who gained weight later on, say around the age of eight or nine, showed no drop in math test scores. Girls who gained weight around first or third grade experienced a score drop, but bounced back by the time they took the tests again in fifth grade.
Which is not to say that obesity makes kids stupid. The paper notes that obese kids report feeling "anxiety, loneliness, low self-esteem, and sadness," and also raises the question of teacher bias.
"It is possible that children with weight problems do more poorly in school because their social skills and peer relationships are compromised," the study reads. "From an early age, children with weight problems are not viewed as desirable playmates or friends."
The study appears in the latest issue of Child Psychology.