Overweight girls, but not boys, may be more likely to have behavioral problems when they start kindergarten, according to the results of a nationwide study.

“The message for parents from our research would be that it is the child’s home environment that influences not only their obesity but also their behavioral health,” Dr. Ashlesha Datar of the research organization RAND in Santa Monica, California, told Reuters Health. “Therefore providing a healthy environment at home is essential for children to be healthy in the early school years.”

But overweight girls who started kindergarten without any behavioral problems were not at increased risk of developing problems by the end of first grade, Datar and co-author Dr. Roland Sturm report in the Archives of Pediatrics and Adolescent Medicine.

So even though being overweight was associated with behavior problems in girls at the start of kindergarten, it may not cause girls to develop behavior problems during the early school years, according to Datar.

“In fact, we find that family characteristics - in particular, low family income and mother’s mental health - were stronger predictors for developing behavior problems in the early school years,” Datar said.

Datar and Sturm based the findings on almost 10,000 children who were followed for two years after starting kindergarten. About one out of 10 kindergartners was overweight, with boys slightly more likely to be overweight.

Overall, boys of all sizes were more likely to have behavior problems than girls, as reported by their parents and teachers.

But among girls, those who were overweight were about 50 percent to 80 percent more likely to have behavioral problems than girls who were not overweight. Among boys, weight was not associated with any significant behavioral differences.

Datar said that the research did not get into the possible explanations for the differences between boys and girls. “But previous research in this area that has also found gender differences suggests that body image and overweight concerns are more common among overweight girls compared to boys,” she said.

Despite the association between overweight and behavioral problems in girls starting kindergarten, being overweight was not associated with developing new behavioral problems by the end of first grade in boys or girls.

Instead, for both boys and girls, having a low family income and a depressed mother were both associated with greater odds of developing behavioral problems, the study found.

One of several areas that need more research, Datar said, is the impact of obesity on children who start school with behavioral problems, such as whether their behavioral problems become worse because of being overweight.

Datar also noted that the study looked at obesity only at the start of kindergarten. “We need to examine the impact of persistent or long-term overweight as well,” she said.

Datar added that children in the study should be followed for a longer time “to determine whether the effects of early childhood obesity manifest themselves in adolescence when body image and weight perceptions tend to be more important.”

SOURCE: Archives of Pediatrics and Adolescent Medicine, August 2004.