Final answer:
About 34 percent of U.S. teens have a BMI at or above the 85th percentile. Obesity in children is defined when the BMI is greater than the 95th percentile for their age group. BMI is used to indicate overweight and obese status, but has limitations and does not account for muscle mass.
Step-by-step explanation:
About 34 percent of U.S. teens have a body mass index (BMI) at or above the 85th percentile. Obesity in children and adolescents is defined by comparing BMI with reference values that are based on large samples. For children, obesity is diagnosed when a child has a BMI greater than the 95th percentile of the reference values for children of the same age. In adults, obesity is diagnosed with a BMI greater than 30 kg/m², and morbid obesity is defined as having a BMI over 40. It's important to note that BMI is a relative measure of body weight in relation to height and has certain limitations, as it does not account for muscle mass in individuals such as athletes.
Childhood obesity is a concerning trend and can lead to significant health issues including type 2 diabetes and heart disease. The measure of BMI is used as a tool to assess this, with BMI values between 25 to 29.9 being considered overweight for adults, and values greater than 30 being considered obese.