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Last updated January 31, 2020. 9 minute read

Morbid obesity—risk factors, diagnosis, and treatment

Morbid obesity is defined as having a body mass index (BMI) over 35. While eating more calories than needed is the cause of morbid obesity, genetics, medications, and other health conditions can play a major role.

Meagan Morris Photo Written by Meagan Morris
Reviewed by Tzvi Doron, DO

As a human, you are so much more than your weight. Sure, weight is one peek into your overall health, but it doesn’t show the whole picture. That said, understanding where your weight falls on the medical spectrum—underweight, normal, overweight, obese, or morbidly obese—can help you get a better idea of your risk for potential health problems down the line.

If you’re curious about morbid obesity or think your weight might be considered to be morbidly obese, read on. We’re getting into the details about this condition, its risk factors, and what it potentially means for your overall health, both now and in the future.

What is obesity?

In simple terms, obesity means having too much fat on the body. Your weight comes from a variety of sources, including muscle, bone, water, and body fat. While you need to have some body fat to maintain proper health, having too much of it can potentially cause certain weight-related health problems (Medline Plus, n.d.).

But how do you know how much body fat makes you obese? Healthcare providers often use body mass index (BMI) as a quick-and-easy way to determine where a person’s weight falls. BMI is calculated using a formula that uses your height and weight, but it doesn’t take into account the other parts of your body that influence your weight (like muscle mass).

BMI is broken out into four categories:

  • Underweight (BMI below 18.5)
  • Normal (BMI of 18.5 to 24.9)
  • Overweight (25 to 29.9)
  • Obese (BMI of 30 or above)

According to the National Institutes of Health, one in three adults is considered to be obese, while about one in 13 adults is considered to be morbidly obese.


  • Morbid obesity is defined as having a body mass index (BMI) over 35.
  • About one in thirteen adults is considered to be morbidly obese.
  • While eating more calories than needed is the cause of morbid obesity, genetics, medications, and other health conditions can play a major role.
  • People with morbid obesity can reverse it through a healthy lifestyle, medications, and weight-loss surgeries.

What is morbid obesity?

A person is considered obese if BMI is higher than 30. There are different levels of obesity, broken down three main categories:

  • Class 1: BMI is 30 to 34.9
  • Class 2: BMI is 35 to 39.9
  • Class 3: BMI is 40 or above

According to the U.S. Centers for Disease Control and Prevention, morbid obesity is considered as having a BMI above 35 but less than 40. A BMI above 40 is sometimes referred to as severe obesity or extreme obesity because health risks increase dramatically when BMI is higher than 35 (CDC, 2017).


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Risk factors for morbid obesity

The simple explanation for morbid obesity is that a person is eating more calories than necessary without burning them off through activity. The amount of calories you need to eat per day is largely dependent on your age and lifestyle (meaning someone who exercises a lot will need to eat more than someone who doesn’t exercise at all). This typically works out to somewhere around 1,600 to 2,400 calories per day for women over 18 and 2,000 to 3,000 calories per day for adult men (ODPHP, 2015).

While eating more calories than are burned is always the cause of weight gain, certain other factors are shown to have an impact on weight.

Family history and genetics

Your genetics and family can have an impact on your chances of morbid obesity, both directly and indirectly. 

Children born to obese parents are more likely also to be obese than children with one or more lean parents. One study found that boys who have overweight parents are 1.7 times more likely to be overweight than their peers with ideal body weight parents—and the results were similar for girls (Bahreynian, 2017).

Genetic factors may also influence obesity. For one study, researchers overfed male twins by the same amount for several weeks. At the end of the study, many of the twins differed in how much weight they gained—and where it accumulated. This led the researchers to believe that genetic factors do influence obesity in some way (Xia, 2013).


Weight gain is not only influenced by the number of calories you eat but how many you burn off during the day. Ideally, a person should get at least two-and-a-half hours of moderate-to-vigorous physical activity each week, but many people aren’t meeting that recommendation with about only one in three getting enough activity.

In general, the more active a person is, the less likely that obesity will become a problem. The inverse of that is true, too: The more sedentary a person is, the more likely he or she is to gain weight over time.


Morbid obesity can happen at any age, but hormonal changes that come with age—coupled with decreased activity—can be a factor. Recent statistics show that obesity levels increase as a person ages, with 42.8 percent of middle-aged adults between 40 and 59 and 41 percent of adults 60 and over being considered obese (Jura, 2016; CDC, 2018). 

Certain medical conditions

While pregnancy is one of the most obvious conditions that can cause weight gain, there are multiple disorders and conditions that bring the potential for weight gain. Hypothyroidism—a condition that causes a person’s metabolism to work slower than normal—is also shown to have an impact on weight (Sanyal, 2016). 

Polycystic ovarian syndrome (PCOS) affects the fertility of approximately five million American women of childbearing age (CDC, 2019). The imbalance of hormones in women with PCOS often causes insulin resistance, which, in turn, can cause weight gain. 

Certain medications

A number of medications prescribed by healthcare providers are shown to cause, or contribute to, weight gain.

Some medications used to treat depression and anxiety are shown to cause a modest increase in weight over time. Other medications used to treat diabetes and other mental disorders are also shown to be related to weight gain, as are birth control pills, some seizure medications, and corticosteroids.

While the exact reason why medications influence weight isn’t clearly understood, they are shown to affect brain functions that control metabolism and appetite.

Signs and symptoms of morbid obesity

While you can’t always tell if a person is morbidly obese by just looking at them, a large buildup of excess fat—especially around the stomach and hips—is one indicator.

People with morbid obesity often have other physical symptoms due to the accumulation of excess fat, including having difficulty with physical activities like walking. They can also have trouble breathing and get easily winded.

How is morbid obesity diagnosed?

Morbid obesity is most often diagnosed by healthcare providers using BMI.

Obesity can also be diagnosed by body fat percentage. In general, a woman with more than 33 percent body fat and a man with more than 25 percent body fat is considered to be obese. Waist circumference is also used to diagnose obesity: Women with a waist larger than 35 inches can be considered to be obese, as is a man with a 40-inch or larger waist (Mayo Clinic, n.d.).

Health risks associated with morbid obesity

While being morbidly obese doesn’t automatically mean a person will develop health issues and medical problems, it is a risk factor for many chronic diseases. 

Type 2 diabetes

Roughly 85 percent of people with type 2 diabetes are overweight or obese (Harvard, 2012). Morbid obesity increases the risk of developing the disease, but research shows that it can go into remission when a person loses as little as 10 percent of their body weight (Dambha-Miller, 2019).

Heart disease

Being morbidly obese increases a person’s risk of developing cardiovascular disease, including heart attacks, peripheral artery disease, arrhythmias, and heart failure. Not only that, but a high BMI can cause heart disease at a younger age (Khan, 2018).


Having obesity is a major risk factor for strokes (Strazzullo, 2010). They happen when the blood supply to the brain is blocked and can result in everything from muscle weakness to brain damage and even death. 

High blood pressure

One 44-year study found that obesity accounted for 26 percent of hypertension cases in men and 28 percent in women (Encyclopedia of Epidemiology, n.d.).

Sleep apnea

Morbid obesity is shown to cause sleep apnea because the excess weight puts unnecessary pressure on the upper airways, making it difficult to breathe. Losing a small percentage of body weight can decrease the severity of sleep apnea by upwards of 50 percent (Schwartz, 2008).


Arthritis (osteoarthritis) is a syndrome that causes joint degeneration and affects more people than any other type of joint disease. 

Morbid obesity is one of the risk factors of osteoarthritis because weight-bearing joints—like the knees—aren’t made to carry around excessive weight. Research shows that U.S. adults with obesity are 6.8 times more likely to develop osteoarthritis of the knee than people with normal weight (King, 2013).

Some cancers

Obese people are shown to have consistent low-level inflammation, which can cause DNA damage over time. This can lead to certain cancers. For example, those with obesity are at an increased risk of developing Barrett esophagus, a gastroesophageal reflux disease that is shown to be a likely cause of esophageal adenocarcinoma (NIH, 2017).

Thyroid, multiple myeloma, kidney, endometrium, and colon cancers are among other types of cancers linked to obesity (NIH, n.d.).

Treatment for morbid obesity

Morbid obesity can be reversed, but it does take time and effort to go from morbidly obese to a healthy weight. Treatment options range from lifestyle changes to surgery—and each comes with advantages and disadvantages.

Diet and exercise

As mentioned earlier, losing just 5 to 10 percent of body weight can sharply decrease an obese patient’s chances of developing obesity-related health problems. A pound of fat is made of approximately 3,500 calories, so cutting down on your calorie intake by 500 calories—or increasing your calorie burn by 500 a day—can lead to approximately one pound of weight loss per week (Medline Plus, n.d.).

Weight loss medications

While there is no magic pill that’ll help you lose weight, there are certain medications shown to help reduce weight when used with a healthy diet and exercise routine. 

The U.S. Food and Drug Administration has approved six medications for weight loss: Orlistat (Xenical), Lorcaserin (Belviq), Phentermine-topiramate (Qsymia), Naltrexone-bupropion (Contrave), and Liraglutide (Saxenda). Each FDA-approve weight loss medication has its own benefits and side effects (NIDDK, 2016). It’s important to note that phentermine is only for short-term use. 

Weight loss surgeries

Weight-loss surgery—also called bariatric surgery—is shown to be the most effective treatment for people with morbid obesity to lose weight. Along with weight loss, surgery can also help reduce the risk of obesity-related health problems and can improve quality of life and life expectancy (Suter, 2009).

There are four main types of weight loss surgery used in the United States: laparoscopic adjustable gastric band (sometimes called gastric banding), gastric sleeve surgery (also called sleeve gastrectomy), and gastric bypass. The fourth type of operation, biliopancreatic diversion with duodenal switch, is also used, but not as common as other types of weight loss surgery (NIDDK, n.d.).

It’s important to see guidance from a healthcare provider before embarking on a journey to losing weight. Your healthcare provider can evaluate your current health to determine which method of weight loss is right for you—and your current health.