Obesity is defined as having a body mass index (BMI) of greater than or equal to 30 kilograms per meters squared (kg/m2; “meters” meaning a person’s height). The categories are designated as follows:[1]
| BMI | Category |
|---|---|
| 25–29.9 | overweight |
| 30–34.9 | class I obesity |
| 35–39.9 | class II obesity |
| ≥40 | class III obesity |
While BMI is a generally useful measurement at the population level, because it only accounts for total body mass, individuals who are tall and/or muscular may have a BMI that qualifies as “obese”. As such, it’s useful to factor other measures like body fat percentage into an evaluation of whether someone has obesity.[2]