The new age group under study is called "tweens" describing the stage between childhood and the teenage years.
The National Heart, Lung and Blood Institute followed 2,300 girls for a decade and found the "tween" years typically between nine and 12 years old are a risky time period for kids to become overweight or obese often because they're not physically active and their hormones haven't kicked in yet to make them want to clean up and spruce up for attention, so to speak.
"You can be skinny at five and have horrible eating habits and be obese when you are fifteen because you never learned to develop appropriate eating habits," said Dr. Nathaniel Beers.
The concern is that road to obesity sets the child up for chronic problems like heart disease which could put these girls at higher risk of premature death as adults. Dr. Beers says one of the best things parents can do is insist their pediatrician track the child's body mass index.