Around 17 percent of American children from age 2 to 19 are classed as “obese”. That’s a level that has remained fairly steady over the last decade. And it’s growing.
Obesity is measured in terms of Body Mass Index (BMI) – a measure that can be used to compare children in terms of their weight. BMI is calculated by dividing a person’s weight in kilograms by the square of their height in meters. For children and teens, BMI is so age- and gender-specific that it is referred to as BMI-for-age. BMI levels among children and teens need to be expressed relative to other children of the same age and gender. Every child is different and that makes it difficult to generalize on something like this.
Overweight is defined as a BMI at or above the 85th percentile and below the 95th percentile for children and teens of the same age and gender. Obesity is defined as a BMI at or above the 95th percentile for children and teens of the same age and gender.
To give an illustration, a 10-year-old boy of average height (56 inches) who weighs 102 pounds would have a BMI of 22.9 kg/m2. He would be considered obese because this calculation puts him in the 95th percentile for BMI-for-age. His BMI is greater than the BMI of 95% of 10-year-old boys in his “reference population”.