Body weight status can be categorized as underweight, healthy weight, overweight, or obese. Body mass index (BMI) is a useful tool that can be used to estimate an individual’s body weight status. BMI is a measure of weight in kilograms (kg) relative to height in meters (m) squared. The terms overweight and obese describe ranges of weight that are greater than what is considered healthy for a given height, while underweight describes a weight that is lower than what is considered healthy for a given height. These categories are a guide, and some people at a healthy weight also may have weight-responsive health conditions. Because children and adolescents are growing, their BMI is plotted on growth charts for sex and age. The percentile indicates the relative position of the child’s BMI among children of the same sex and age.
| category | children and adolescents (BMi for age Percentile range) | adults (BMi) |
| underweight | Less than the 5th percentile | Less than 18.5 kg/m2 |
| Healthy weight | 5th percentile to less than the 85th percentile | 18.5 to 24.9 kg/m2 |
| overweight | 85th percentile to less than the 95th percentile | 25.0 to 29.9 kg/m2 |
| obese | Equal to or greater than the 95th percentile | 30.0 kg/m2 or greater |