Morbid obesity, now more commonly called class III obesity or severe obesity, is a complex condition that significantly increases the risk of serious health problems. It occurs when the body develops an excessive number and size of fat cells. People with class III obesity have a body mass index (BMI) of 40 or higher. BMI is a quick tool used by healthcare providers to evaluate weight in relation to height.

The National Institute of Diabetes and Digestive and Kidney Diseases estimates that about 9.2% of U.S. adults live with severe obesity. Risk factors include unhealthy eating patterns, low physical activity, certain chronic conditions, medications, and genetics. Fortunately, severe obesity can be managed and even reversed through lifestyle changes, medications, or surgery.

Symptoms of class III obesity

The symptoms of severe obesity vary by individual, but the most obvious sign is excess adipose tissue (fat). When large amounts of fat accumulate around the waist, the risk of chronic conditions increases.

Common symptoms include:

  • Larger waist circumference

  • Skin irritation from folds rubbing together

  • Body aches and back pain

  • Joint pain

  • Fatigue

  • Snoring and sleep disturbances

  • Shortness of breath

  • Low self-esteem

Causes

Severe obesity develops when the body consumes more calories than it uses, creating an imbalance. Excess energy is stored as fat, and over time, this buildup of fat cells leads to obesity or severe obesity.

Risk factors

Several factors may increase the risk of developing severe obesity:

Eating habits: Diets high in sugar and saturated fat promote weight gain.
Physical activity: Sedentary lifestyles contribute to energy imbalance.
Accessibility: Limited access to healthy food and safe spaces to exercise.
Sleep: Lack of quality sleep disrupts hormones and appetite regulation.
Stress: Chronic stress increases the risk of weight gain.
Health conditions: Disorders such as metabolic syndrome, hypothyroidism, Cushing’s syndrome, and PCOS.
Medications: Certain drugs, including hormonal birth control, antidepressants, and beta-blockers.
Family history: Genetics and family history of obesity or metabolic disorders.

Diagnosis

Most healthcare providers use BMI to diagnose obesity, but it has limitations. BMI only measures weight relative to height and does not consider age, gender, muscle mass, ethnicity, or body composition.

Waist circumference is another important measure. People with more abdominal fat are at higher risk of heart disease, high blood pressure, and diabetes. Risk increases when waist circumference is:

  • 35 inches or more for people assigned female at birth

  • 40 inches or more for people assigned male at birth

Treatments for severe obesity

Treatment focuses on weight reduction, lowering adipose tissue, and reducing health risks. Options include lifestyle changes, medications, surgery, and medical devices.

Lifestyle changes

  • Create a nutritious eating plan with the guidance of a dietitian.

  • Engage in at least 150 minutes of moderate-to-intense physical activity weekly.

  • Consider weight-loss counseling for professional support.

Medications
Some medications approved for obesity include:

  • Alli (orlistat)

  • Qsymia (phentermine-topiramate)

  • Contrave (naltrexone-bupropion)

  • Saxenda (liraglutide)

  • Wegovy (semaglutide)

  • IMCIVREE (setmelanotide)

These drugs may suppress appetite, alter fat absorption, or regulate metabolism, but side effects are possible.

Surgery
For individuals with BMI ≥ 40, weight-loss surgery may be recommended. Options include:

  • Gastric sleeve: Removes most of the stomach, leaving a small pouch.

  • Gastric bypass: Creates a small stomach pouch connected to the small intestine.

  • Adjustable gastric band: Places a band around the stomach to reduce intake.

Devices
Newer approaches include:

  • Inflatable balloon: Temporarily fills space in the stomach to reduce hunger.

  • Gastric emptying device: Allows removal of food after meals to limit absorption.

Prevention

Many cases of severe obesity can be prevented. Strategies include:

  • Eating a balanced diet rich in fruits, vegetables, whole grains, and lean proteins

  • Limiting sugar and processed foods

  • Exercising regularly

  • Sleeping at least 7 hours per night

  • Managing stress through mindfulness, hobbies, or therapy

Complications

Severe obesity increases the risk of multiple chronic conditions, including:

  • Type 2 diabetes

  • Heart disease and high blood pressure

  • Stroke

  • GERD and gallbladder disease

  • Pancreatitis and liver disease

  • Sleep apnea and kidney disease

  • Certain cancers (endometrial, breast, ovarian, prostate)

  • Asthma and arthritis

  • Infertility, pregnancy complications (gestational diabetes, preeclampsia)

  • Dementia, anxiety, and depression

Living with obesity

Severe obesity often impacts both physical and mental health. Depression, anxiety, and stress are common. Support groups and organizations can provide encouragement and resources.

Examples include:

  • Obesity Action Coalition

  • American Obesity Foundation

  • Obesity Care Advocacy Network

  • Academy of Nutrition and Dietetics

A quick review

Morbid obesity (class III obesity) is a chronic and serious condition caused by excessive fat accumulation. While challenging, it is both treatable and preventable.

Healthy eating, daily physical activity, adequate sleep, and stress management are key preventive steps. Medical options, including medications and surgery, can also be effective in reducing risks and improving overall health.