Conditions InDepth: Obesity

Obesity is defined as an abnormally high proportion of body fat. Obesity occurs when calorie intake is consistently greater than the number of calories burned through activity and basic metabolic processes.

Several factors can influence obesity, including:

  • Genetic tendency
  • Eating habits
  • Activity level
  • Biologic factors (such as the amount and activity of certain chemicals in the body)
  • Medications (such as corticosteroids, antidepressants, and antipsychotics)
  • Underactive thyroid gland
  • Cushing's disease
  • Polycystic ovary syndrome
  • Fröhlich's syndrome
  • Prader-Willi syndrome
  • Laurence-Moon-Biedl syndrome

According to the World Health Organization, there are more than 300 million obese adults and 1.1 billion overweight people worldwide. And this number continues to rise. A similar pattern is apparent in the US. According to data from the Center for Disease Control (CDC), in 2006, 66.3% of adults age 20 and over are overweight, while approximately 30% are obese. (Overweight and obese are defined as a body mass index [BMI] greater than or equal to 25 and 30, respectively.)

Further, the number of American children who are overweight also continues to rise. Among Americans between the ages of 6-19, approximately 15% are overweight as of 1999-2000—or triple what the percentage was from 1980. (Overweight among children is based on BMI-for-age growth charts.) A combination of genetic factors, poor eating habits, and low activity levels accounts for the vast majority of the overweight and obesity in the United States.

Obesity can lead to other health problems, such as:

  • Decreased energy
  • High blood pressure
  • Heart disease and stroke
  • Type 2 diabetes
  • Gallstones
  • Worsening arthritis symptoms
  • Increased risk of certain cancers
  • Blood clots
  • Skin breakdown and infections
  • Gout
  • Infertility
  • Sleep apnea
  • Poor self-image
  • Depression

What are the risk factors for obesity?
What are the symptoms of obesity?
How is obesity diagnosed?
What are the treatments for obesity?
Are there screening tests for obesity?
How can I reduce my risk of obesity?
What questions should I ask my healthcare provider?
Where can I get more information about obesity?


American Obesity Association website. Available at: .

Flegal KM, Carroll MD, Ogden CL, Johnson CL. Prevalence and trends in obesity among US adults, 1999-2000. JAMA . 2002;288:1723-1727.

Harrison's Principles of Internal Medicine . 14th edition. McGraw-Hill;1998.

Ogden CL, Flegal KM, Carroll MD, Johnson CL. Prevalence and trends in overweight among US children and adolescents, 1999-2000. JAMA . 2002;288:1728-1732.

Center for Disease Control website. Available at .

Last reviewed February 2007 by Edward R. Rosick, DO, MPH, MS

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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