Class III obesity, formerly known as morbid obesity, is a complex chronic condition that can lead to several serious health issues. There are many treatment options for class III obesity, including healthy lifestyle changes, behavioral and psychological therapy, medication and surgical procedures.
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.
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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.”
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:
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:
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:
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.
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:
Class III obesity is a common condition. Approximately 9% of adults in the United States had class III obesity from 2017 to 2018.
Class III obesity is a complex disease that has several contributing factors. The main cause of why your body stores fat is that there’s an imbalance between the number of calories (energy) you consume and the number of calories (energy) your body uses. In other words, consuming more calories than your body uses for essential bodily processes, such as digestion and breathing, and for physical activity in a day causes your body to store fat, resulting in weight gain.
However, there are several other factors that contribute to how much food we eat, the type of food we eat and how our body uses that energy. Every person’s body is unique and metabolizes energy differently. Some people are at a greater risk of weight gain than others, and class III obesity is rarely caused by a lack of willpower to lose weight or a lack of “control” in the amount of food you eat.
Several factors contribute to developing obesity, including:
There are no specific symptoms of class III obesity. The signs of class III obesity include having a body mass index (BMI) of 40 or higher and/or an unhealthy body fat distribution that healthcare providers estimate by measuring your waist circumference and skin thickness. Class III obesity can cause side effects and complications in many parts of your body.
Healthcare providers diagnose class III obesity in part by determining a person’s body mass index (BMI). BMI is defined by the ratio of your height to your weight. Optimum BMI ranges from 20 to 25. An adult may be considered to have class III obesity if they meet one of the following criteria:
The BMI scale isn't always accurate for certain populations, and healthcare providers use a different scale to determine obesity in children.
Healthcare providers also use waist circumference measurements to help diagnose obesity.
In adults who aren't pregnant, a waist circumference over 35 inches for females or over 40 inches for males can help diagnose obesity. If you’re of South Asian or Central and South American descent, your provider may use smaller waist circumference values to diagnose obesity. People from these backgrounds often don’t show signs of a large waist circumference even though they may have unhealthy amounts of fat deep in their abdomens and may be diagnosed with obesity.
Providers can also estimate obesity by measuring skin thickness in the following areas of your body:
Healthcare providers may order certain laboratory tests to assess your health to see if you have any health conditions that could be causing weight gain and/or that are highly associated with class III obesity. These tests may include:
Treatment for class III obesity is very individualized. Every person is unique and thus requires a treatment plan that’s specific to their situation and goals. Together, you and your healthcare provider can come up with a plan that treats underlying secondary causes of obesity and manages health conditions related to obesity, if you have any.
Treating class III obesity involves a multi-prong strategy. Management for class III obesity may include:
Certain lifestyle changes can help you manage obesity, improve your overall health and/or lose weight, including:
Your healthcare provider may recommend enrolling in individual or group behavioral weight-loss programs to help treat obesity. In these programs, a specially trained healthcare provider will customize a weight-loss plan for you.
Mood disorders, such as depression and anxiety, occur at high rates among people with obesity. Because of this, your provider may also recommend psychological therapy if you have a mental health condition.
Different types of behavioral and psychological therapies that can help treat obesity include:
When healthy lifestyle changes are not enough, your healthcare provider may recommend treating obesity with FDA-approved medications. These medications work by affecting your brain or gastrointestinal tract:
Weight-loss medications are not recommended as a single treatment for class III obesity. Like all medications, they have different side effects, and some should not be taken if you have certain conditions or are taking certain medications. Together, you and your provider will determine if weight loss medication is right for you.
If you have class III obesity and lifestyle changes and weight loss medications aren't working for you, you may be eligible for one of the following bariatric surgery procedures:
Surgical procedures for weight loss have certain risks and benefits. Be sure to talk to your healthcare provider about possible side effects and complications.
In general, complications that can occur shortly after surgery include:
Longer-term complications can include:
There are several risk factors for class III obesity. Some risk factors can be changed, such as lifestyle habits. Other risk factors, such as age, genetics, race and ethnicity cannot be changed. Healthy lifestyle habits can decrease your risk of developing obesity.
Risk factors for developing obesity include:
While you can’t change some risk factors for obesity, it’s important to remember that healthy lifestyle changes can help decrease your risk of developing obesity.
If your BMI or other medical assessments indicate that you’re getting close to having obesity or if you have certain risk factors, your healthcare provider may recommend developing healthy lifestyle changes to try to prevent you from developing obesity. Lifestyle changes include:
These recommendations will be specific to your health and situation. Talk to your healthcare provider and/or a registered dietitian about setting healthy and obtainable goals.
If left untreated, class III obesity may shorten life expectancy up to 14 years. In addition to contributing to potentially serious health problems, class III obesity is associated with reduced economic and social opportunities and reduced quality of life.
It is possible to treat class III obesity and improve health outcomes. Research shows that some people who have obesity and take prescription weight management medications lose 10% or more of their starting weight. Studies on bariatric surgery results have revealed that people who undergo bariatric surgery may lose 30% to 50% of their excess weight in the first six months and 77% of excess weight 12 months or more after surgery. Another study revealed that people who had bariatric surgery could maintain a 50% to 60% loss of excess weight for 10 to 14 years after surgery.
It can be daunting and overwhelming to try to lose weight and change lifestyle habits. If you have class III obesity, it’s important to remember that even a 5% to 10% weight loss from your starting weight can significantly improve your health by lowering blood sugar (glucose) levels, blood pressure and triglyceride levels. It can also improve your quality of life.
Class III obesity is a serious medical condition that can contribute to the development of several health conditions, including:
Managing your weight or losing weight can be daunting. It’s important to remember that changing lifestyle habits takes time and patience. The following tips may help you stay committed to your health goals and lifestyle changes:
If you think you may have obesity or class III obesity, it’s important to see your healthcare provider so they can assess your overall health and prescribe treatment, if necessary.
If you’re having a difficult time managing your weight, contact your healthcare provider. They may run some tests to see if you have any underlying conditions that are causing weight gain.
If you have class III obesity, it may be helpful to as your healthcare provider the following questions:
A note from Cleveland Clinic
Class III obesity is a serious health condition that can lead to complications and a decreased quality of life. The good news is that your healthcare provider can tailor several treatment options to you and your health needs and goals. It can be daunting and challenging to try to lose weight and change lifestyle habits. Know that your medical team is there to support you in reaching your health goals.
Last reviewed by a Cleveland Clinic medical professional on 11/02/2021.
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