What Is Obesity?

Obesity is a chronic disorder that affects tens of millions of Americans. Caused by a complex variety of factors, obesity is a major risk factor for serious health problems, including coronary heart disease (CHD), high blood pressure, stroke, diabetes and certain forms of cancer. Obese people are also at high risk for depression and job discrimination and other social problems owing to our fat-phobic society. Most worrisome is research indicating that obese people have a shortened life expectancy.

According to the American Obesity Association, a nonprofit educational and advocacy group, obesity causes some 300,000 premature deaths each year and accounts for an estimated $100 billion in annual health care costs.

After cigarette smoking, obesity is the second-leading cause of preventable deaths in the US.

Obesity is generally evaluated using the body mass index (BMI). BMI is not perfect because it doesn't take into account a person's fat-to-muscle ratio (muscle takes up less space but weighs more than fat). But BMI is considered reliable for assessing obese populations.

To determine your BMI, your weight in kilograms is divided by your height in meters, squared. If your BMI is 25 to 29.9, you are overweight but not to the point of being obese. If your BMI is 30 or greater, you are considered obese. Obesity would most likely be diagnosed in the following cases:

• A 6-foot-tall individual who weighs 221 pounds



• A 5-foot, 5-inch-tall person who weighs 180 pounds

Anyone whose BMI is 40 or above or is 100 pounds overweight is considered severely (morbidly) obese. For example, severe obesity would be diagnosed in the following cases:

• A 5-foot, 3-inch-tall person who weighs 226 pounds



• A 6-foot, 1-inch person who weighs 303 pounds

Another measure used to assess obesity is waist circumference. Excess abdominal fat is an independent predictor of disease risk. Research indicates that a waist circumference of more than 40 inches in men and more than 35 inches in women raises the risk of diabetes and CHD.

Distinguishing between being overweight and being severely obese is important when determining a patient's risk factors for disease and the best treatment approach.

Related Articles What Causes Obesity? Health Consequences of Obesity Reversing Obesity Finding a Sound Weight-Loss Program Obesity Treatments

External Sources National Heart, Lung, and Blood Institute National Institute of Diabetes and Digestive and Kidney Diseases American Obesity Association

This article was reviewed and updated June 2007.

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