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Department of Surgery
Bariatric Surgery


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What is the Body Mass Index?

Physicians often use the Body Mass Index to determine a person’s weight risks. The BMI compares weight to height. When a person’s BMI is greater than 30, that person is considered obese. When a person’s BMI exceeds 40, that person is considered morbidly obese.

Your BMI can be calculated here.

BMI Classification

< 18.5 = underweight
18.5–24.9 = normal weight
25.0–29.9 = overweight
30.0–34.9 = class I obesity
35.0–39.9 = class II obesity
≥ 40.0 = class III obesity

You can also visit the Centers for Disease Control to learn more about obesity.


Centers for Disease Control and Prevention: Obesity and Overweight Topics

Obesity definitions

Center for Disease Control and Prevention: Defining Overweight and Obesity

Table of weight, height and BMI

National Heart Lung and Blood Institute: Obesity Guidelines