Table 1.

Classification of overweight and obesity by BMI^∗.

Classification	BMI (kg/m2)	Obesity class
Underweight	<18.5
Normal	18.5–24.9
Overweight	25.0–29.9
Obesity	30.0–34.9	I
	35.0–39.9	II
Extreme obesity	40.0+	III

^∗Adapted from the World Health Organization [11].

Body mass index (BMI) is a simple index of weight for height that is commonly used to classify underweight, overweight, and obesity in adults. It is defined as the weight in kilograms divided by the square of the height in meters (kg/m²).