Research has suggested that obesity is related to poorer academic performance beginning as early on as kindergarten. Studies have found that obese students, especially girls, tend to have lower test scores than their slimmer peers, are more likely to be held back a grade, and are less likely to continue on to college.

The latest study, published this week in the journal Child Development, followed 6,250 children from kindergarten through fifth grade and found that those who were obese throughout that period scored lower on math tests than non-obese children.

Interestingly, this pattern held when researchers took into account extenuating factors that can influence both body size and test scores, such as family income, race, the mother’s education level and job status, and both parents’ expectations for the child’s performance in school.

“In boys and girls alike who entered kindergarten with weight problems, we saw these differences in math performances emerge at first grade, and the poor performance persisted through fifth grade,” says lead researcher Sara Gable, Ph.D., an associate professor of nutrition and exercise physiology at the University of Missouri-Columbia.

The question is whether the actual state of obesity influences student achievement, or whether it is something related to the obesity but not the actual pounds.

A study published last year found that adolescents’ self-perception of their weight was more strongly associated with academic performance than BMI, suggesting that self-esteem and other intangibles may have a big influence.

What remains unclear is whether obesity causes emotional problems or vice versa. Obesity has the potential to weaken social skills if a child becomes isolated due to bullying or stigmatization. On the contrary, poor social skills can lead to sadness, which can lead to poor eating habits and to weight gain if a child turns to food for comfort.

Social and emotional problems may just be one piece of the puzzle. It is possible that some of the well-documented health problems associated with childhood obesity, such as asthma, diabetes, and sleep disorders, may interfere with schoolwork or cause kids to miss class.

Most likely, a combination of factors probably best explains the link between obesity and academic performance. Either way, parents will want to be aware of the many risks and issues related to obesity, and will want to do their best to instill healthy eating habits in their children, to promote and encourage exercise and to do their best to keep their children in a healthy weight range.