Identifying Childhood Obesity
Right off the bat, I can give you two pieces of good news:
To determine what weight category your child your child is in, you first must calculate your child's Body Mass Index (BMI). This is a reasonably accurate screening tool that helps decide if your child is the right weight for their height. (The height is squared to account for tall stature or else all tall children would be considered overweight!) However, BMI does not take into account bone or muscle density, so if you think your child is big-boned or is a muscular athlete, further testing by a health professional may be needed to determine body-fat percentage more accurately. After all, it is excess body fat that is the health risk in obesity, not muscle!
Use the CDC's BMI calculator to determine BMI for your child.