Body Mass Index (BMI) is a guideline of weight in relation to height that can be used to classify a child as obese or overweight. Using the BMI-for-age percentile growth chart from the CDC, a BMI at or above the 85th percentile for children and teens of the same age is classified as overweight; a BMI at or above the 95th percentile is classified as obese; and a BMI above the 99th percentile is classified as severe obesity.
Childhood obesity can also be categorised into two types: exogenous obesity, caused by external factors that create an imbalance between energy intake and expenditure, and endogenous obesity, caused by genetic, syndromic, or endocrine factors.