Strict mothers were nearly five times more likely to raise tubby first-graders than mothers who treated their children with flexibility and respect while also setting clear rules.

But while the children of flexible rule-setting moms avoided obesity, the children of neglectful mothers and permissive mothers were twice as likely to get fat.

"The difference between the different parenting groups is pretty striking," said the study co-author, Dr. Kay Rhee of Boston University School of Medicine. The study of 872 families appears in the June issue of Pediatrics, released Monday.

Rhee speculated that parents who show respect and warmth within a framework of rules may help their children learn to make good decisions about food and exercise. Or it could be that strict parents create a stressful household where overeating becomes a comfort and escape, she said.

Other studies have shown the flexible parenting style, also called authoritative, has other good results for children such as higher achievement in school and lower incidence of depression, said John Lavigne, chief psychologist at Children's Memorial Hospital in Chicago.

Lavigne, who was not involved in the new study, said most parents can learn a different way of handling their children.

"Some parents might have difficulty changing their style. But a lot of other parents are very amenable to change, if they only have the right kind of advice," Lavigne said.

Not enough fathers participated in the study to measure their effects on children's weight, Rhee said. And since more than 80 percent of the study participants were white, the findings may not be applicable to other racial groups, she said.

The study also did not take into account the weight status of the mothers, so the researchers couldn't rule out that a mother's weight might influence both her parenting and her children's weight. However, a previous study showed that parenting style is not linked to weight status, Rhee said.

To determine parenting style for the new study, researchers surveyed the mothers and observed them interacting with their children when the kids were 4 years old. The children's body mass indexes were measured later when the children were in first grade.

Seventeen percent of the children of strict disciplinarians were overweight compared to 9.9 percent of the children of neglectful parents, 9.8 percent of the children of permissive parents and 3.9 percent of the children of flexible rule-setters.

"Children need adults to set some limits and as the child matures they need to learn responsibility and self-regulation gradually," said Dr. Nancy Krebs, co-chair of the task force on obesity for the American Academy of Pediatrics, who also was not involved in the new study.

The researchers studied mothers and children in Little Rock, Ark.; Irvine, Calif.; Lawrence, Kan.; Boston; Philadelphia; Pittsburgh; Charlottesville, Va.; Morgantown, N.C.; Seattle, and Madison, Wis.

In homes where parents are firm but flexible, "the rules can be bent a little or modified a little to accommodate the situation. But ultimately there are rules," Rhee said. "You still maintain the rule that the child has to have a vegetable at dinner, but the child gets to pick which one and how much of it they eat."