Class III Obesity (Morbid Obesity): Causes, Symptoms, Risks & Treatment

What is morbid obesity (now known as class III obesity)?

Class III obesity, formerly known as morbid obesity, is a complex chronic disease in which a person has a body mass index (BMI) of 40 or higher or a BMI of 35 or higher and is experiencing obesity-related health conditions. The BMI scale is not always accurate, so healthcare providers may use other tests and tools to assess obesity, such as measuring waist circumference.

Class III obesity can contribute to the development of several serious health conditions, such as Type 2 diabetes and heart disease. The good news is that class III obesity is manageable and treatable.

Why was class III obesity called morbid obesity?

The term “morbid obesity” was coined by two healthcare providers in 1963 in order to justify insurance reimbursement for the cost of intestinal bypass surgery for weight loss in people with a BMI over 40.

In a medical setting, “morbidity” means illness or disease. Healthcare professionals also often use the term “comorbidity,” which means that an individual has more than one illness or disease occurring at the same time. The medical meaning of “morbid” is appropriate in describing this type of obesity since class III obesity is considered a disease and is often associated with other chronic health conditions.

The problem is that, like many words, “morbid” has another meaning. Outside of the medical setting, “morbid” means disturbing or unpleasant. Since most people aren’t familiar with the medical definition, they connected morbid (class III) obesity and people with obesity to those negative words. The use of “morbid” in describing obesity adds to the false and problematic societal stigma that suggests that people with obesity lack the willpower to lose weight, when this is almost always not the case.

Now, healthcare providers, researchers and health organizations, such as the World Health Organization (WHO), use the term “class III obesity” in place of “morbid obesity.”

What is body mass index (BMI)?

Body mass index (BMI) is a screening tool that measures the ratio of your height to your weight. Healthcare providers calculate BMI by using weight in kilograms (kg) divided by the square of height in meters (m2). In most people, BMI relates to body fat, but it’s not accurate in some cases. BMI alone does not diagnose body fatness or health. Healthcare providers use BMI and other tools and tests to assess someone’s health status and risks.

The following BMI ranges (in kg/m2) classify different weight types:

• Underweight: Less than 18.5.
• Optimum range: 18.5 to 24.9.
• Overweight: 25 to 29.9.
• Class I obesity: 30 to 34.9.
• Class II obesity: 35 to 39.9.
• Class III obesity: More than 40.

BMI is not always an accurate representation of an individual’s health. For example, if you have more or less muscle than what is considered optimal, your BMI may not be an accurate measurement of how much body fat you have. In addition, you could have health conditions that are highly associated with having class III obesity, such as Type 2 diabetes or high blood pressure, without having obesity.

The standard BMI scale is often not accurate for the following people:

• Bodybuilders and professional athletes: Since muscle is more dense than fat, people who are very muscular may have a high BMI even though they have optimal levels of fat.
• People older than 65: For people over the age of 65, it’s often better to have a BMI between 25 and 27, rather than under 25. This is because a slightly higher BMI may help protect them from developing weakened bones (osteoporosis).
• Children: While many children have obesity, you shouldn’t use the standard BMI chart to evaluate a child’s weight. Talk to your child’s healthcare provider about the optimum weight range for your child’s age and height.

The standard BMI scale may also be inaccurate for people of different races when assessing their risk for certain health conditions. Studies have shown that, in general, people of Asian descent are more likely to have health risks at a much lower BMI, and Black people are more at risk for health issues at a higher BMI than what is considered at-risk in the standard scale.

As an example of BMI inaccuracies according to race, the standard cutoff BMI number associated with a higher risk of developing Type 2 diabetes (T2D) varies for people of different races. Differences include:

• A BMI of 23.9 and or above is linked to a higher risk of T2D for people of South Asian descent.
• A BMI of 26 or above is linked to a higher risk of T2D for people of Arabic descent.
• A BMI of 28 or above is linked to a higher risk of T2D for Black people.
• A BMI of 30 or above is linked to a higher risk of T2D for white people.

What is the difference between having obesity and having class III obesity?

In most — but not all — cases, adults with a body mass index (BMI) of 30 to 39.9 are considered to have obesity. Adults with a BMI of 40 or higher are considered to have class III obesity.

Who does class III obesity affect?

Anyone can develop class III obesity, including children and adults. However, due to its complexity, class III obesity tends to affect people differently. Based on a study on the prevalence (commonness) of class III obesity in adults in the United States between 2017 and 2018, here’s how class III obesity affects different people:

• Sex: Approximately 11.5% of women and people assigned female at birth have class III obesity compared to 6.9% of men and people assigned male at birth.
• Age: Class III obesity affects 11.5% of adults aged 40 to 59, 9.1% of adults aged 20 to 39 and 5.8% of adults aged 60 and over.
• Race: Non-Hispanic Black adults had the highest prevalence of class III obesity at 13.8%, and non-Hispanic Asian adults had the lowest at 2.0%.

How common is class III obesity?

Class III obesity is a common condition. Approximately 9% of adults in the United States had class III obesity from 2017 to 2018.