What Are Obesity Classes? Understanding How the Obesity Grading System Can Impact Treatment
Updated on March 31, 2026
ON THIS PAGE
ON THIS PAGE
Obesity grading is a way that healthcare providers classify different types of obesity. An individual is considered to have obesity if they weigh more than what is deemed healthy for their specific height. Obesity can increase one’s risk of developing other serious conditions, such as diabetes, heart disease, and cancer.
The obesity grading system divides obesity into three main groups. It uses body mass index (BMI), a ratio of weight to height, to categorize a person’s obesity class. Healthcare providers may also use waist circumference measurements and other tools to assign an obesity class.
Obesity class categories can help doctors recommend more tailored, appropriate treatment for people with obesity, as well as better predict their health outcomes.
How Obesity Classes Are Defined
Experts generally rely on BMI measurements to define obesity classes. Calculate your BMI by dividing your weight in kilograms (kg) by the square of your height in meters (m2). There are also many online tools to help you determine your BMI, such as the BMI calculator from the Centers for Disease Control and Prevention.
Although BMI can be a helpful tool, it’s not an accurate health assessment for everyone. For instance, a person with a lot of lean muscle mass (which is naturally heavier than fat mass) may have a high BMI but not necessarily have obesity. On the other hand, a person may not have a very high BMI but still experience complications from excess body weight, especially if they’re older or have low muscle mass. For this reason, healthcare providers may use other methods — such as waist circumference measurements, skin thickness assessments, and body composition scales — to diagnose obesity.
What Are the Obesity Classes?
The different obesity classes and their associated risk of other health problems, or comorbidities, are categorized as follows.
Obesity Class
BMI Range
Risk of Comorbidities
Overweight
25.0 to 29.9
—
Class 1
30.0 to 34.9
Low risk
Class 2
35.0 to 39.9
Moderate risk
Class 3
40.0 or higher; or 35.0 and higher with obesity-related health problems; or 100 lb over the recommended body weight for your height
High risk
Some doctors and researchers further divide class 3 obesity into two categories:
- Super Obesity BMI of 50 to 59.9
- Super-Super Obesity BMI of 60 or more
Does Obesity Class Affect Health Risks and Outcomes?
All classes of obesity can increase a person’s chances of developing other health conditions. Potential health risks associated with obesity include the following:
- Breathing problems, such as asthma or obesity hypoventilation syndrome
- Certain types of cancer
- Depression
- Diabetes
- High blood pressure
- High cholesterol and triglyceride levels
- Heart problems, such as arrhythmia (irregular heart rhythm), coronary artery disease, and heart failure
- Liver problems
- Osteoarthritis
- Reproductive and sexual health problems
- Sleep apnea
- Stroke
While these risks can affect anyone with obesity, people with class 3 obesity tend to have the worst outcomes. The higher your BMI and the higher your obesity class, the greater your odds of having other obesity-related health problems.
For instance, for every five-unit increase in BMI, a person’s risk for coronary heart disease increases by 30 percent. Additionally, every unit increase in BMI increases one’s risk of developing atrial fibrillation (an irregular heartbeat) by 5 percent.
A greater degree of obesity also raises a person’s overall mortality risk. Class 3 obesity is associated with substantially elevated mortality rates as a result of obesity complications and may shorten a person’s life expectancy by up to 14 years.
Do Treatment Options Differ by Obesity Class?
Available treatments for obesity include lifestyle changes, medications, surgery, and therapy. Knowing a person’s specific class of obesity can help doctors determine which treatments may be most beneficial.
Lifestyle Changes
Lifestyle changes are an important part of treatment for all obesity classes. The following approaches can help promote weight loss:
- Diet Changes Consuming fewer calories and eating more whole and minimally processed foods can help you better manage your weight. A slow but consistent approach usually works best. If you have obesity, consider working with a registered dietitian-nutritionist who can help you come up with an eating plan.
- Exercise Physical activity can help you shed pounds. The baseline recommendation for all adults, including those with obesity, is a minimum 150 minutes of moderate-intensity exercise a week, which should include full-body strength training twice a week. People with obesity are encouraged to aim for 200 to 300 minutes of exercise each week.
- Behavior Modification Programs Individual and group counseling, as well as peer support groups, can help you implement and stick with the healthy lifestyle changes needed to manage obesity successfully.
Medications
Weight loss medications are an option for people with class 1, class 2, and class 3 obesity. Individuals with a BMI of 27 to 29.9 (in the overweight class) may also be candidates if they have at least one obesity-related health condition.
Common medications used to treat obesity include the following:
- diethylpropion (Tenuate)
- liraglutide (Saxenda)
- naltrexone-bupropion (Contrave)
- orlistat (Alli)
- phendimetrazine (Bontril)
- phentermine-topiramate (Qsymia)
- semaglutide (Wegovy)
- tirzepatide (Zepbound)
Surgery
Weight loss surgery, known as bariatric surgery, is typically an option for adults with a BMI of 35 or higher, or a BMI of 30 or higher with obesity-related comorbidities; or for those in whom medication and lifestyle changes aren’t working.
The newest recommendations from the American Society for Metabolic and Bariatric Surgery and the International Federation for the Surgery of Obesity and Metabolic Disorders suggest that bariatric surgery should be recommended for all adults with class 2 and class 3 obesity regardless of whether they have other health conditions. They also recommend surgery for adults with class 1 obesity and a metabolic disease, especially type 2 diabetes. Surgical guidelines differ for children, adolescents, and people of Asian heritage.
Common bariatric procedures include the following:
- Gastric Sleeve Surgeons remove a large part of the stomach and leave behind a smaller part, which resembles a sleeve.
- Gastric Bypass A small part of the stomach is connected to the middle of the intestine, allowing food to flow through the smaller part and bypass the upper intestine.
- Biliopancreatic Diversion With Duodenal Switch This surgery involves two separate procedures. First, a surgery similar to gastric sleeve is performed. Then the small intestine is divided into two tracts. Food moves through one of them and bypasses most of the small intestine.
Therapy
Counseling and behavior modification programs can help people with obesity reach their weight loss goals. Talking with a mental health professional may help you understand your triggers and change unhealthy habits. Support groups can also be a good forum for connecting with others and sharing your struggles.
The Takeaway
- Healthcare providers use an obesity grading system primarily based on BMI to categorize obesity into three distinct classes.
- Class 1 (a BMI of 30 to 34.9) and class 2 (a BMI of 35 to 39.9) represent increasing levels of health risk, while class 3 (a BMI of 40 or higher, or 35 or higher with comorbidities) indicates the highest risk for developing serious related health conditions and significantly reduced life expectancy.
- Higher obesity classes are directly linked to an increased likelihood of developing comorbidities such as type 2 diabetes, heart disease, sleep apnea, and certain types of cancer.
- Identifying a person’s specific obesity class allows doctors to tailor their treatment, ranging from lifestyle changes and medications to bariatric surgery.
FAQ
Is there a class 4 obesity?
While standard medical guidelines categorize obesity into three classes, some clinicians may recognize a fourth class of obesity, often called super obesity, which is marked by a BMI of 50 to 59.9.
What is class 5 obesity?
An individual with a BMI of 60 or higher is considered to have class 5 obesity, more commonly referred to as super-super obesity. This obesity class is associated with very high health risks.
What BMI qualifies for Ozempic?
Ozempic is prescribed for people with type 2 diabetes regardless of their weight. However, Wegovy is prescribed for people who have a BMI of 30 or higher and those with a BMI of 27 to 29.9 with an obesity-related health condition.
Resources We Trust
- Cleveland Clinic: What’s a Healthy BMI?
- Mayo Clinic: Mayo Clinic BMI and Waist Circumference Calculator
- Centers for Disease Control and Prevention: Adult Obesity Facts
- American Heart Association: Understanding Extreme Obesity and What You Can Do
- American Society for Metabolic and Bariatric Surgery: Disease of Obesity
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
- Health Risks of Obesity. MedlinePlus. July 3, 2025.
- Class III Obesity (Formerly Known as Morbid Obesity). Cleveland Clinic. February 19, 2025.
- Calculate Your BMI. National Heart, Lung, and Blood Institute.
- Al Jazzar RI et al. Super Super Obesity With a BMI of 98 kg/m2: A Case Report. Journal of Surgical Case Reports. January 10, 2024.
- Kivimäki M et al. Body-Mass Index and Risk of Obesity-Related Complex Multimorbidity: An Observational Multicohort Study. The Lancet. April 2022.
- Lim Y et al. Obesity and Comorbid Conditions. StatPearls. June 27, 2024.
- Taieb AB et al. Understanding the risk of developing weight-related complications associated with different body mass index categories: a systematic review. Diabetology and Metabolic Syndrome. December 7, 2022.
- Kermansaravi M et al. Current Recommendations for Procedure Selection in Class I and II Obesity Developed by an Expert Modified Delphi Consensus. Scientific Reports. February 11, 2024.
- Obesity. Mayo Clinic. December 2, 2025.
- Obesity and Exercise. Obesity Medicine Association. January 6, 2025.
- Sombra LRS et al. Pharmacologic Therapy for Obesity. StatPearls. February 12, 2024.
- Prescription Medications to Treat Overweight and Obesity. National Institute of Diabetes and Digestive and Kidney Diseases. June 2024.
- Eisenberg D et al. 2022 American Society for Metabolic and Bariatric Surgery (ASMBS) and International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO): Indications for Metabolic and Bariatric Surgery. Surgery for Obesity and Related Diseases. December 2022.
- Types of Weight-Loss Surgery. National Institute of Diabetes and Digestive and Kidney Diseases. September 2020.
Meet Our Experts
Diala Alatassi, MD, FACP
Medical Reviewer
Diala Alatassi, MD, is a board-certified obesity medicine specialist who is committed to providing comprehensive, compassionate, and personalized care. By integrating medical exper...
Julie Lynn Marks
Author
Julie Marks is a freelance writer with more than 20 years of experience covering health, lifestyle, and science topics. In addition to writing for Everyday Health, her work has bee...