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Understanding Morbid Obesity: BMI Classification, Causes, Symptoms, and Treatment

Written by Andrew Le, MD

UpdatedFebruary 29, 2024

Obesity is a big health issue caused by too much body fat, which leads to lifelong risks. An even more serious form is called morbid obesity.

In 2019, about 40% of Americans were obese, and 18% had morbid obesity. To assess and categorize these risks, health professionals use BMI (Body Mass Index) as a key indicator.

In this article, you will understand morbid obesity, its diagnosis using BMI, what causes it, its signs, the problems it can cause, and how it can be treated.

So, let’s get started.

🔑 Key Takeaways:

  • Morbid obesity is closely linked to obesity-related health issues and can severely affect an individual's well-being
  • The preferred terms for morbid obesity are either "Class III Obesity" or "Severe Obesity."
  • BMI indicates whether an individual's weight is within a healthy range or if they are underweight, overweight, or obese.
  • Around 9% of adults in the US were experiencing morbid obesity between 2017 and 2018.
  • Morbid obesity results from genetic, behavioral, and environmental factors.
  • Healthcare providers may measure waist circumference to assess abdominal fat distribution.
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What is Morbid Obesity?

Morbid obesity is a complex chronic disease characterized by a high BMI within specific ranges. This condition is closely linked to obesity-related health issues and can severely affect an individual's well-being.

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The preferred terms for morbid obesity are either "Class III Obesity" or "Severe Obesity." This change in language aims to communicate the seriousness of the health issue without appearing judgmental, and it contributes to reducing the stigma associated with obesity.

Now, let's understand its effects on people of different ages and backgrounds and how common morbid obesity is.

Demographics

While anyone can develop this condition, certain demographic groups may be more susceptible. Data from a US study reveals the following trends:

  • Sex: In 2017–2018, obesity prevalence was 42.4% in adults, with higher severe obesity rates in women.
  • Age: Severe obesity was most prevalent among adults aged 40–59, and obesity rates increased from 1999–2000 to 2017–2018.
  • Race: Among adults, non-Hispanic black individuals had the highest prevalence of obesity and severe obesity compared to other race and Hispanic-origin groups.

Prevalence

Around 9% of adults in the US were experiencing morbid obesity between 2017 and 2018. The significant prevalence underscores the importance of addressing this health concern through awareness, prevention, and treatment.

How is Obesity Diagnosed Using BMI?

Obesity is diagnosed through BMI. However, the diagnostic process extends beyond just the numerical value of BMI, incorporating a contextual understanding of an individual's health and lifestyle. This is how obesity is identified through BMI:

Calculation of BMI

BMI is a widely used screening tool that estimates an individual's weight-to-height ratio. It is calculated by dividing weight in kilograms by the square of height in meters (kg/m²).

BMI indicates whether an individual's weight is within a healthy range or if they are underweight, overweight, or obese. However, it may not always accurately represent an individual's health status due to variations in muscle mass, age, and other factors.

Obesity Levels Based on BMI

The classification of obesity levels based on BMI includes the following categories:

  • Less than 18.5: Underweight
  • 18.5 - 24.9: Healthy weight
  • 25.0 - 29.9: Overweight
  • 30.0 - 34.9: Class I (Low-risk) Obesity
  • 35.0 - 39.9: Class II (Moderate-risk) Obesity
  • 40.0 or higher: Class III (High-risk) Obesity

This means that a BMI of 40.0 or higher is considered morbid obesity.

🩺 A Doctor’s Note:

BMI's limitations are evident in specific groups: athletes' elevated muscle mass inflates their scores, slightly higher BMI may protect the elderly against osteoporosis, unique assessments are necessary for children, and differing racial groups exhibit varied health risks tied to BMI.

What Causes Morbid Obesity?

Morbid obesity results from genetic, behavioral, and environmental factors.

The primary cause of excessive fat storage leading to obesity is an imbalance between calorie intake and expenditure. Consuming more calories than the body uses for essential functions and physical activity results in the accumulation of excess fat.

💡 Did You Know?

To lose weight, you can eat fewer calories. This means consuming less than you burn. Yet, because Western diets are often high in calories, it's tough to do this alone. Adding physical activity to eating less can make it easier to lose weight.

However, other factors contribute to how much an individual eats, the type of food consumed, and how the body utilizes energy. These factors include:

  • Genetic Factors: Research has shown that genetics play a role in obesity, with certain genes associated with weight gain.
  • Hormone Imbalances: Hormones, such as cortisol and thyroid hormones, influence appetite, metabolism, and fat storage. Stress-related cortisol levels and thyroid imbalances can contribute to weight gain.
  • Socioeconomic and Geographical Factors: Low socioeconomic status, limited access to healthier foods, and a lack of recreational facilities can contribute to obesity.
  • Cultural and Environmental Factors: Advertising, portion sizes, and obesogenic environmental chemicals can influence food choices and energy balance.

What Are the Signs and Symptoms of Morbid Obesity?

The signs and symptoms of morbid obesity can include:

  • Sweating
  • Tiredness
  • Joint and back pain
  • Difficulty breathing
  • Sleep problems, including snoring
  • Difficulty with physical activity
  • Low confidence and feelings of isolation
  • High blood pressure and other symptoms of metabolic syndrome
  • Indications of severe obesity (high buildup of fat around the body, BMI of 40 or above, signs of complications like hypertension)

What Are The Complications Of Morbid Obesity?

Morbid obesity can give rise to a range of complications, affecting various aspects of health. Complications may include:

  • Metabolic syndrome: Characterized by a combination of central obesity, high triglyceride levels, low HDL cholesterol levels, high blood pressure, and elevated fasting blood glucose levels.
  • Type 2 diabetes: Excess fat storage leads to insulin resistance and increased risk of developing type 2 diabetes (T2D).
  • Heart disease: Prolonged exposure to obesity causes worsening cardiac function, larger ventricular mass, systolic dysfunction, and atrial fibrillation.
  • High blood pressure (hypertension): Increased risk due to obesity leads to an elevated heart disease risk.
  • Atherosclerosis: Obesity as a risk factor accelerates plaque development in arteries due to related health conditions.
  • Certain cancers: Elevated risk of various cancers, accounting for a significant percentage of cancer diagnoses.
  • Breathing issues (Obesity Hypoventilation Syndrome - OHS): Disorder causing imbalanced levels of carbon dioxide and oxygen in the blood, potentially leading to serious health problems.
  • Osteoarthritis: Excess weight contributes to joint stress and an increased likelihood of developing or exacerbating osteoarthritis.

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  • Depression: Higher risk of depression among individuals with obesity, with associated mental health concerns.

What other methods can be used to diagnose Morbid Obesity?

Aside from BMI measurements, morbid obesity is also diagnosed through waist circumference and clinical assessments.

The diagnosis involves determining whether an individual meets specific criteria based on weight, height, and related health conditions.

Here’s a closer look at these diagnoses:

Waist Circumference

Healthcare providers may measure waist circumference to assess abdominal fat distribution. Excess abdominal fat is associated with an increased risk of obesity-related health conditions.

For adults, a waist circumference greater than 35 inches for females or greater than 40 inches for males is often used to diagnose obesity. Different waist circumference values might be used for certain populations, such as individuals of South Asian or Central and South American descent.

Clinical Assessment

Healthcare providers also consider other factors, such as obesity-related health conditions, when diagnosing morbid obesity. If a person has a BMI of 35 or more and is experiencing health issues like high blood pressure or diabetes, they may be diagnosed with morbid obesity.

Laboratory Tests

Laboratory tests are often conducted to assess the individual's overall health and identify any underlying medical conditions contributing to obesity or associated with it. These tests can include:

  • Complete blood count (CBC)
  • Basic metabolic panel
  • Kidney function tests
  • Liver function tests
  • Lipid panel
  • Hemoglobin A1C (HbA1C)
  • Thyroid-stimulating hormone (TSH) test
  • Vitamin D levels test
  • Urinalysis
  • C-reactive protein (CRP) test

Additional Assessments

Depending on the individual's health profile, healthcare providers may also recommend additional assessments such as an electrocardiogram (EKG) to evaluate heart health and sleep studies to assess sleep patterns.

💡 Did You Know?

Using an electrocardiogram (EKG), atrial fibrillation (AFib) and atrial flutter (AFL) are diagnosed. AFib is irregular heartbeats, while AFL is similar to the signal from the upper right heart chamber. An EKG tracks heart electrical activity to identify these conditions.

What Are the Treatment Options for Morbid Obesity?

Treatment for morbid obesity is comprehensive and personalized, focusing on healthy lifestyle changes, behavioral interventions, medications, and surgical options:

Healthy Lifestyle Changes

Adopting a heart-healthy diet, increasing physical activity, getting adequate sleep, and managing stress are essential to managing morbid obesity.

Gradual, sustainable changes in diet and exercise habits can contribute to weight loss and overall health improvement.

Behavioral Therapy

Behavioral interventions, such as motivational interviewing, cognitive-behavioral therapy (CBT), dialectical behavioral therapy (DBT), and interpersonal psychotherapy (IPT), can help individuals address emotional and psychological factors influencing their eating habits and weight management.

Medications

In cases where lifestyle changes alone are insufficient, healthcare providers may prescribe medications that help suppress appetite, reduce fat absorption, or address underlying metabolic issues. These medications should be used under medical supervision.

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Surgical Procedures

Bariatric surgery, including gastric bypass, sleeve gastrectomy, and gastric banding, may be recommended for individuals with severe obesity or those without sufficient weight loss through other methods. Surgical interventions can lead to significant weight loss and improved health outcomes.

The Bottomline

Morbid obesity isn't an illness but can lead to serious health problems, even life-threatening ones like Metabolic syndrome. In many cases, severe obesity can be reversed.

Among those with morbid obesity, fewer than 5% manage to lose a lot of weight and keep it off through non-surgical methods, usually using a mix of diet, behavior changes, and exercise.

If you're concerned about obesity or its signs, getting medical advice is crucial. Treatments can help manage weight and reduce the risk of severe complications.

🗒️ Related Articles:

To learn more about weight management, check out some of our articles:

FAQs on Morbid Obesity and BMI

How do I know if I am overweight?

You fall within the overweight range if your BMI is between 25.0 and less than 30. A BMI of 30.0 or higher is classified as obesity.

What organs are affected by obesity?

Obesity can impact various organs, including the endocrine, cardiovascular, mental health, and liver.

Can obesity be cured?

Obesity can be managed and reduced through calorie reduction and healthier eating habits. Gradual, steady weight loss is the safest and most effective for long-term results.

What is the #1 cause of obesity?

Diet and lifestyle factors, such as consuming high amounts of processed food and excess alcohol, contribute to obesity.

Why is BMI important?

BMI estimates body fat and helps assess disease risk. Higher BMI correlates with higher risks of conditions like heart disease, diabetes, and certain cancers.

Is BMI a good indicator of health?

BMI provides a population-level indicator of health, but assessing fat distribution and waist circumference might offer better disease risk predictions.

What is the first-line treatment for obesity?

Lifestyle changes involving diet, exercise, and behavior therapy are the initial approach for weight management. These changes can lead to significant weight loss.

Illustration of a healthcare provider asking questions on a smart phone.
Virtual weight loss solution
A personalized GLP-1 medication program delivered to you via our partner Korb Health
Illustration of a healthcare provider asking questions on a smart phone.
  • Free consultation; program starts at $269/mo
  • Checkmark Inside Circle.Customized online program and wellness coaching
  • Prescription medications and supplies shipped to your door