Understanding Morbid Obesity

If you've been hearing more about obesity, there's a reason: It continues to increase such that the American Obesity Foundation has issued a rallying cry to fight the "obesity pandemic."

In fact, from 1999 to 2020, the prevalence rose from 30.5% to 41.9%. During the same years, morbid obesity (also known as extreme obesity and class 3 obesity) increased from 4.7% to 9.2%.

The American Medical Association responded to these trends in 2013 by designating obesity a complex, chronic disease. It also acknowledged the “enormous humanitarian and economic impact of obesity as requiring the medical care, research, and education attention of other major global medical diseases.”

A close up of a blood pressure gauge

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Today, morbid obesity affects at least 6.9% of men and more than 11.5% of women. Health experts remain focused on morbid obesity so they can understand it better and improve treatment options. Morbid obesity may have your attention because it can lead to serious health problems.

This article explains how obesity is measured by body mass index. It also describes the three classes of obesity, how morbid obesity is defined, and the possible causes and complications of obesity. Treatment options and the prognosis for morbidly obese people end this article on a high note.

Obesity vs. Morbid Obesity

Like obesity, morbid obesity is measured by body mass index (BMI). The index is a ratio of someone's height to their weight. In other words, it is your weight (in kilograms) divided by the square of your height in meters.

BMI is a dated, flawed measure. It does not take into account factors such as body composition, ethnicity, sex, race, and age. 
Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.

Once you have your BMI number, you can determine where your measurement falls:

  • If your BMI is less than 18.5, it falls within the underweight range
  • If your BMI is 18.5 to 24.9, it falls within the healthy weight range
  • If your BMI is 25 to 29.9, it falls within the overweight range
  • If your BMI is 30 or higher, it falls within the obesity range

Obesity is divided into three categories.

Type of Obesity  BMI
Class 1 (moderate obesity) 30 to 34.9 
Class 2 (severe obesity)  35 to 39.9 
Class 3 (morbid obesity) 40 and over

Class 3 obesity is known as morbid or extreme obesity. Healthcare providers can take it even one step further, defining someone with morbid obesity as having:

  • A BMI of 40 or more or having an “ideal body weight” more than 100 pounds greater than outlined in life insurance tables
  • A lack of obesity-related glandular problems (known as endocrine disorders) caused by obesity
  • Medical problems associated with severe obesity are called comorbidities. The presence of these problems means that someone who is interested in bariatric surgery may have a BMI of 35 (not 40). The surgery is also known as weight-loss surgery.

Condition Affects People of All Ages

Nearly 75% of American adults ages 20 and older are overweight or obese. Meanwhile, nearly 20% of children and teens ages 2 to 19 are obese.

Definitions Matter

In fact, these categories and classifications exist for other reasons beyond helping people assess whether they're obese or morbidly obese. The divisions are also used as guidelines to determine which patients may be eligible for weight-loss surgery and weight-loss medications.

Put another way, a formal diagnosis of morbid obesity, based on a BMI measurement of 40 or greater, may qualify a patient for treatment with bariatric surgery or certain anti-obesity medications.

Such measurements can also indicate a level of risk for obesity-related disorders, such as cancer, cardiovascular disease, heartburn, obstructive sleep apnea, and Type 2 diabetes. The risk of many of these disorders increases in proportion to the rise in BMI.

Obesity Diminishes Function

Obesity is a serious condition that can interfere with even the most basic functions of life, like breathing.

Causes of Morbid Obesity

An excessive caloric intake and lack of exercise are two factors that can increase the risk of developing obesity. While other causes aren't fully understood, medical experts single out some likely contributors. They include:

  • Genetics. Research shows that as many as 80% of people with obesity may have inherited the condition.
  • Poor sleep habits. Not getting enough sleep or not getting enough quality sleep is another contributing factor.
  • Certain health conditions. Conditions such as metabolic syndrome or polycystic syndrome (PCOS). The former is a group of conditions that puts someone at risk for diabetes, heart disease, and stroke. The latter is a common hormonal disorder among people of childbearing age.
  • Some medications. Several medications can cause weight gain. These include antidepressants, antipsychotics (drugs used to treat psychotic disorders), beta blockers (used to treat high blood pressure), birth control, glucocorticoids (used to treat autoimmune diseases), and insulin (taken by diabetics to control blood sugar).
  • Stress. Stress can cause the body to make more cortisol, a hormone that affects appetite and energy levels. Hormone changes can deliver a double whammy, causing someone to eat more and store more fat.

Risks and Complications of Morbid Obesity

People who are obese know that the disease can interfere with even the most basic daily activities, like breathing and walking. This means they could become easily winded and struggle to keep pace with someone who walks a short distance.

The complications of obesity and morbid obesity can also run the gamut from serious to life-threatening. It's not always possible, though, to draw a stark, black line between the two. Not every complication is as clear-cut as, say, arthritis. For example, for every 2-pound increase in weight, the risk factor for arthritis increases by 9% to 13%.

In general, the greater the class of obesity—from class 1 to class 3—the greater the complication tends to be. (And the worse a patient may feel.)

A healthcare provider who is privy to someone's full medical history is the best judge of determining exactly how serious a complication may be. The provider sees the full picture.

The provider may see that the complications (the effects) of obesity are linked to a wide range of activities and conditions. They can be broken down from everyday to life-threatening complications.

Physical effects:

  • Climbing stairs
  • Exercising
  • Shortness of breath
  • Walking

Everyday living effects:

  • Lifting
  • Self-care activities
  • Shopping
  • Working

Mental/psychological effects:

  • Drop in self-esteem
  • Isolation
  • Sadness/depression

Serious effects:

Life-threatening effects (or those capable of reducing life expectancy):

Like Scales, Tape Measures Never Lie

People with abdominal obesity tend to carry excess fat in their midsection. They have belly fat that makes them look apple-shaped. More significantly, they are at greater risk for diabetes and cardiovascular disease. Men with a waist size of 40 or more and women whose waist is larger than 35 inches are considered to have abdominal obesity.

Treatment of Morbid Obesity

If you're diagnosed with morbid obesity, consider it a first but hugely important step toward reducing these complications while improving your health and quality of life.

A treatment program may involve a group of healthcare professionals, like a registered dietitian and nutritionist, exercise physiologist, psychologist, and maybe a bariatric healthcare provider. This team will work together to create a safe and customized weight-loss plan for you.

The plan most likely will involve several tactics—often a combination of behavioral changes, dieting, exercise, medicine, and perhaps weight-loss surgery. Research shows that multiple approaches can result in the most successful outcome. ”Successful” means losing excess weight safely and keeping it off by:

Changing Behavior

Modifying your behavior includes adopting a reduced-calorie diet and physical activity program. It begins by setting realistic, short- and long-term weight-loss goals and, perhaps, keeping a food and exercise diary.

This diary can help identify triggers that may cause you to overeat and avoid them, reward new behaviors (like starting a fitness activity), and perhaps adopt new attitudes about body image. Setting a regular sleep schedule and developing a support network (family, friends, coworkers) to help can be important, too.


Following a low-calorie diet means eating more healthy foods, eating fewer unhealthy foods, and eliminating fatty, processed foods. Calorie reduction often isn't done overnight but gradually, until you're consuming 500 to 1,000 calories a day less than you burn.


The long-term key to success isn't so much figuring out what level of physical activity is right for you; this is usually the easy part. Finding an enjoyable outlet is the part that may require some experimentation.

After all, physical exertion can be difficult for morbidly obese people. This is why (at the beginning, at least), exercise may involve parking your car farther and farther away from doors and pedaling an under-the-desk bike for short periods several times a day.

Taking Weight-Loss Medications

Medications approved by the U.S. Food and Drug Administration (FDA) include:

  • Beta-methyl-phenylethylamine (Fastin), a stimulant that increases fat metabolism
  • Orlistat (Xenical), which blocks about 30% of dietary fat from being absorbed
  • Phentermine, an appetite suppressant
  • Sibutramine (Meridia), which is another appetite suppressant

Having a Weight-Loss Device Implanted

Weight-loss devices include a gastric balloon, gastric band, and gastric-emptying system. These devices have been shown to help morbidly obese people lose 5% of their body weight.

The devices function differently, so ask your healthcare provider to explain the best option for you.

Undergoing Bariatric Surgery

Surgery could involve having a portion of the stomach removed, shrinking the size of the stomach, or creating a detour around the first part of the intestine so that you get full more quickly. To be considered for bariatric surgery, someone must have a BMI of 40 or greater or weigh more than 100 pounds over their recommended body weight.

Small Loss Brings Big Results

Healthcare professionals are fond of telling their patients that even a weight loss of 5%
can significantly improve health and quality of life. It's more than an encouraging pick-me-up; it's the truth.

Prognosis for Morbid Obesity

People who are morbidly obese have a two to three times higher risk of developing a life-threatening disease, compared to those who do not have a BMI in the morbidly obese range.

This is why morbidly obese women face a future that is cut by 12 years; the life expectancy of morbidly obese men is reduced by 16 years.

Compared to these risks, many health experts are moved to agree with the stance of New York-Presbyterian Columbia University Medical Center: “The risks associated with medically severe obesity are greater than the risks associated with its surgical treatments.”

In fact, surgery appears to be the best way to a healthier life for morbidly obese people. It's true that they can lose weight and keep it off with a combination of other treatments, like behavior modification, dieting, and exercise. This is especially true when a program is guided by a certified weight-loss professional. But the number of morbidly obese people who succeed is rather small, at about 5%.

By contrast, the success rate for bariatric surgery tends to be high—by some estimates as high as 80%.

But even surgery should not be regarded as a shortcut to committing to losing weight and living a healthier life. Many surgeons, for example, ask that patients embark on a holistic weight loss program before being considered for bariatric surgery.

Even then, surgeons often want a patient to “demonstrate serious motivation and a clear understanding of the extensive dietary, exercise and medical guidelines that must be followed for
the remainder” of a patient's life.

With incentives like this, it's no wonder that most morbidly obese people celebrate the day they can call themselves “formerly obese.”

Obesity Adds Up

An obese person has medical costs that are about $1,800 higher than someone with a healthy weight. Altogether, the medical costs of obesity in America was $173 billion in 2019.


Obesity and morbid obesity are measured by someone's body mass index, which is a ratio of height to weight. Someone is morbidly (or severely) obese if they have a BMI of 40 or more or have an “ideal body weight” more than 100 pounds greater than is considered healthy. Morbid obesity can also be traced to heredity, poor sleep, and environmental influences.

The list of potential health problems associated with morbid obesity is very long. And many health issues are serious or life-threatening. Several types of surgery remain good options. But whether or not patients pursue weight-loss surgery, they are often encouraged to adopt a comprehensive approach to losing weight and keeping it off.

Benefits Require Close Look

You may wonder if someone with morbid obesity can get disability benefits. The answer is far from clear-cut. Technically, the Social Security Administration does not consider morbid obesity to be a disability. But it does acknowledge that morbid obesity is a risk factor for some disabling conditions. So someone who is morbidly obese may be eligible for benefits if they also have at least two of the following conditions: arthritis, chronic pain, heart disease, high blood pressure, sleep apnea, or type 2 diabetes.

A Word From Verywell

Before 2013, some people considered obesity to be self-inflicted. The AMA's designation of obesity as a chronic disease didn't exactly create a sea change in attitudes—except maybe hush some critics. So what's the lesson? The naysayers are still out there. So it doesn't really matter what other people say; it matters only what you think. The support is there to help you succeed with a full-on weight loss approach. If you're determined to turn a page to a healthier way of life, you can do it.

Frequently Asked Questions

  • What is the success rate of bariatric surgery?

    About 80% of patients achieve success over the long term.

  • Do I have to be in good health to have this surgery?

    No, and most patients aren't. They often grapple with poor health because of their obesity. They may have high blood pressure, heart problems, or breathing problems.

  • Are there risks involved in weight-loss surgery?

    There are risks involved in every type of surgery. In this case, sometimes patients experience bleeding, an infection, an obstruction of the intestine, a hernia, or the rejection of the suture material. Surgeons are trained to keep an eye on and respond quickly to such developments.

15 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. American College of Cardiology/American Heart Association Task Force on Practice Guidelines, Obesity Expert Panel, 2013. Expert Panel Report: Guidelines (2013) for the management of overweight and obesity in adults. Obesity. 2014;22 Suppl 2:S41-S410. doi:10.1002/oby.20660

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  8. University of Rochester Medical Center. Obesity.

  9. New York-Presbyterian Columbia University Medical Center. Center for Metabolic and Weight Loss Surgery. Obesity: Understanding its causes and risks.

  10. U.S. Department of Health and Human Services. National Heart, Lung, and Blood Institute. Overweight and obesity. Causes and risk factors.

  11. Medicover Hospitals. Morbid obesity.

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  13. University of California-San Francisco. Obesity treatments.

  14. Penn Medicine. Princeton Health. Frequently asked questions.

  15. Disability Approval Guide. Can you get disability benefits for morbid obesity?

Additional Reading

By Yasmine S. Ali, MD, MSCI
Yasmine Ali, MD, is board-certified in cardiology. She is an assistant clinical professor of medicine at Vanderbilt University School of Medicine and an award-winning physician writer.