And for both boys and girls who are persistently overweight from kindergarten through third grade, these feelings of depression, anxiety and loneliness get worse over time, Dr. Sara Gable of the University of Missouri in Columbia and her colleagues found.

"I think there's a tendency to believe that boys don't experience those consequences until later," Gable told Reuters Health. "These findings suggest that they are experiencing some of these negative consequences earlier than may have been believed."

Her study included 8,000 children divided into three different groups: those who were overweight through kindergarten, first grade and third grade; kids who were only overweight as third graders; and kids who were never overweight. Gable and her team looked at teachers' perceptions of students in kindergarten, first grade, and third grade, and also had children fill out questionnaires about their own well-being.

Teachers rated the girls who were overweight throughout the study, as well as those who only were overweight in third grade, as having worse interpersonal skills than girls who were never overweight. They also viewed overweight girls as having less self-control, and the differences seen between the heavy girls and normal-weight girls increased over time.

However, a boy's weight status had no influence on how a teacher perceived his social or self-control skills. Heavy boys were actually viewed as showing fewer aggressive, acting-out behaviors than normal weight boys, while the opposite was true for girls, with overweight girls seen as showing more of these "externalizing" behaviors.

Children who were overweight at any point during the study also perceived themselves as having worse interpersonal skills, lower social standing, and worse peer relationships. The heavy children also reported having more "internalizing" behaviors, such as social withdrawal or depression.

The fact that teachers' different perceptions of overweight children extended to those who were technically overweight for the first time in third grade suggests that even children who may have been on the heavy side of "average" early-on experience discrimination, Gable said."

Overweight shouldn't be seen as an "either-or" proposition, according to the researcher, but as a continuum. And both parents and pediatricians should pay attention to a child's weight status even before he or she is officially overweight, Gable added.

How to help kids slim down is far from clear, she acknowledged. And working parents are also faced with major obstacles to helping their kids be more active and eat healthier, she added, which are only getting worse with the economic slump.

Parents simply need to do what they can, Gable said, from offering a child a plain carrot instead of a carrot slathered with ranch dressing, or having kids draw and color instead of watching TV. "In terms of what's the solution -- for families it's baby steps," she said.