What is the difference between obese and morbidly obese

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The term “obesity” gets thrown around a lot, and sometimes it may not be clear what it means. Does it refer to anyone who is overweight or has some excess weight to lose? Or is it more than that? Well, there is a medical definition of obesity, as well as for the term overweight.

What Is Overweight?

The medical definition of overweight is based on body mass index (BMI). BMI is measured in units of kg/m2, which means it requires height and weight for the calculation.

Overweight is defined as a BMI of 25.0 – 29.9 kg/m2. A normal BMI is defined as falling between 18.5 and 24.9. Having a BMI lower than 18.5 classifies one as being underweight.

Body Mass Index (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.

In medical terminology, the word “overweight” has come to be used as a noun (as in, “obesity and overweight”) as much as an adjective. Such usage has the effect of making clear that overweight and obesity are part of a disease process—more on that below.

BMI calculators are readily available to use, such as the one offered right here. Just enter your information to learn your BMI.

What Is Obesity?

Just as for overweight, the medical definition for obesity hinges on the BMI calculation. To be classified as obese, a patient must have a BMI of 30.0 or greater. A BMI of 40.0 or greater is often referred to as “morbid obesity,” and is recommended by national guidelines as the cutpoint for identifying patients who may be eligible for bariatric surgery.

It should be noted, of course, that certain athletes who are highly muscular may have a high BMI that is due to their greater muscle weight rather than to body fat. Thus, BMI is intended to be part of a greater clinical assessment.

Why Does It Matter?

Many studies have shown that the likelihood of poorer health outcomes (in terms of such diseases as cancer, cardiovascular disease, obstructive sleep apnea, diabetes, high blood pressure, and others), as well as overall premature death, increases as BMI increases. And the clinical definition of obesity (BMI of 30.0 or greater) is used in many cases to determine appropriate treatment options.

There are also implications for insurance coverage and what therapies would be considered medically necessary. In 2013, the American Medical Association (AMA) officially declared obesity to be a disease, acknowledging the “enormous humanitarian and economic impact of obesity as requiring the medical care, research, and education attention of other major global medical diseases.”

Also in 2013, the American Heart Association (AHA), American College of Cardiology (ACCF), and The Obesity Society (TOS) released new, long-awaited obesity guidelines, which were published as the “2013 ACCF/AHA/TOS Guideline for the Management of Overweight and Obesity in Adults.”

The impact of officially acknowledging obesity as a chronic disease is expected not only to raise awareness of the problem among the general public, but also to impact policy at all levels. Policymakers may feel greater need to fund and implement obesity treatment and intervention programs, while third-party payers may be more likely to reimburse physicians and other healthcare professionals for treatment and management of obesity as a recognized disease.

As far as the Centers for Medicare and Medicaid Services (CMS) are concerned, obesity has been categorized as a chronic illness since 2004. Since 2011, Medicare has covered the cost of behavioral therapy for patients with a diagnosis of obesity. This may consist of screening with BMI and waist circumference, dietary assessment, and high-intensity behavioral interventions. Coverage for bariatric surgery is also available under certain criteria.

Coverage under private health plans may vary; however, under the 2010 Affordable Care Act (ACA), new health plans are required to cover preventive services that are rated “A” (strongly recommended) or “B” (recommended) by the U.S. Preventive Services Task Force (USPSTF). Obesity screening has been given a “B” recommendation for both adults and children by the USPSTF, and thus new health plans will be required to cover obesity screening, which, as noted above, usually starts with BMI screening and may include waist circumference and dietary assessment. Further coverage by health plans for other obesity-related management options and interventions, however, will likely continue to vary. Some insurers, for instance, offer telephone counseling, while others offer health coaching or referrals to weight-loss services such as Weight Watchers.

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.

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.

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