BMI obesity classes 1, 2 and 3 explained
Review the three adult obesity classes by BMI and learn why the category is only one part of risk assessment.
Adult BMI values of 30.0 and above are commonly divided into three classes:
| Class | BMI |
|---|---|
| Obesity class 1 | 30.0–34.9 |
| Obesity class 2 | 35.0–39.9 |
| Obesity class 3 | 40.0 or above |
The classes describe increasing BMI bands; they do not reveal an individual’s body composition, symptoms or exact health risk. Risk is shaped by many factors, including waist size, blood pressure, glucose and lipid levels, sleep, fitness, smoking, family history and existing conditions.
The term “class 3 obesity” is generally clearer and less stigmatizing than older labels such as “morbid obesity.” Respectful language matters because the category is a clinical descriptor, not a description of a person.
Use the BMI calculator to verify the value before rounding. A health professional can place a result of 30 or higher in context and discuss evidence-based options. BMI alone should not be used to self-diagnose or begin an extreme diet.