For an 8-year-old girl, a body mass index (BMI) that falls between the 5th and 85th percentile is considered a healthy BMI, as reported by Akron Children's Hospital. A BMI less than the 5th percentile is considered underweight, while BMIs higher than the 85th percentile are overweight. Children with BMIs above the 95th percentile are considered obese.
Pediatricians plot a child's BMI over time to track his or her growth and help determine if there is a weight problem. Children often go through a growth spurt and experience a sudden increase in BMI that later returns to an area near their charted levels.
Children who are athletic may fall in the overweight or obese category due to their high amount of muscle mass, even though they have a healthy amount of body fat.