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Obese vs. morbidly obese or class III: What's the difference?

By Jenilee Matz, MPH Oct 09, 2023 • 2 min

In the U.S., more than one-third of adults have obesity. This label is used to describe a weight range that’s higher than what’s considered healthy for a certain height. Severe obesity, formerly known as morbid obesity, is a subcategory of obesity.

What is the definition of obesity?

Obesity is a serious condition characterized by having excess body fat that increases the chance of health problems. These include heart diseasehigh blood pressuretype 2 diabetessleep apnea, some types of cancer, mental health conditions and more. People with obesity can face a reduced quality and length of life.

What is an obese BMI?

The Centers for Disease Control and Prevention (CDC) says obesity occurs when you have a body mass index (BMI) of 30 or higher. BMI is a screening tool that estimates body fat in adults. It can determine if you’re underweight, at a healthy weight, overweight or obese. To learn your BMI, take your weight in kilograms and divide it by the square of your height in meters.

Obesity is further divided into subcategories. As your BMI goes up, so does your risk for health complications. Obesity classes include:

  • Class I obesity: BMI of 30–34.9
  • Class II obesity: BMI of 35–39.9
  • Class III obesity: BMI of 40 and higher

What is morbid obesity?

Class III obesity may also be called severe obesity. It was previously known as morbid obesity.

Obesity increases the risk of many health issues. The goal of treating obesity is to reach and maintain a healthy weight. Know that even if you haven’t had success with weight loss efforts before, there are many ways to treat obesity and reduce your health risks. Your treatment may include lifestyle changes, weight management programs or weight loss medications, devices or surgery. Ask your healthcare provider what options are best for you.

Clinically reviewed and updated October 2023.

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