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Diagnosis of Obesity

Obesity is an abnormally high proportion of body fat. The doctor can often determine if you are obese by looking at your body and assessing the percentage of body fat. Methods of assessing body fat are discussed below.

Measuring your weight in relation to your height is the traditional way of determining whether you are overweight, obese, or at an appropriate weight. Your doctor can often determine if you are overweight or obese by calculating your body mass index (BMI). This can be done by dividing your weight in kilograms by your height in meters squared. Your BMI can easily be calculated using a height and weight table. The BMI calculation does not take into account whether your weight is composed mostly of fat or muscle. Some muscular people may have a high BMI without being overweight or obese.

In addition, there is risk associated with abdominal fat build up, even if your total weight is not high. So measuring the circumference of your waist is also an important measure of whether you need to lose weight.

There are other tests that can estimate your percentage of body fat. The accuracy of these tests varies and some are so expensive that you are not likely to have them at the doctor’s office. When combined with your visual appearance and waist circumference, your BMI can usually provide a valid estimate of whether you are overweight or obese.

Tests to diagnose obesity include:

  • BMI—A BMI of 25 to 29.9 is considered overweight and 30 or higher is considered obese for adults.
  • Waist circumference, sagittal diameter, and waist-to-hip ratio—Simple measurements that estimate the amount of fat deposited in the skin and inside the abdominal cavity. Waist-to-hip ratio greater than 1 in men or greater than 0.8 in women is considered obese. Waist circumferences that exceed 102 centimeters (40 inches) men or exceed 88 centimeters (35 inches) in women are associated with an increased risk of heart disease.
  • Skinfold caliper—Most fat is deposited beneath the skin. This test measures fat just beneath the skin, but cannot measure fat inside the abdomen.
  • Water displacement tests—Fat floats, but the rest of your body tissues sink. Determining how well you float provides an estimated ratio of fat to body mass.
  • Electrical measurements—A couple of tests calculate your percentage of body fat by measuring the difference between the electrical characteristics of fat and other tissues in your body.
  • Blood tests—To rule out other medical conditions that may cause excess body weight, such as thyroid or adrenal disorders

Revision Information

  • Aim for healthy weight. National Heart, Lung, and Blood Institute website. Available at: Accessed February 27, 2014.

  • Barlow SE, Expert Committee. Expert Committee recommendations regarding the prevention, assessment, and treatment of child and adolescent overweight and obesity: summary report. Pediatrics. 2007;120(Suppl):S164-S192.

  • Deurenberg P, Deurenberg-Yap, Guricci S. Asians are different from Caucasians and from each other in their body mass index/body fat percent relationship. Obesity Rev. 2002;3(3):141-146.

  • Deurenberg-Yap M, Schmidt G, van Staveren WA, Deurenberg, P: The paradox of low body mass index and high body fat percentage among Chinese, Malays and Indians in Singapore. Int J Obes Relat Metab Disord. 2000;24(8):1011-1017.

  • Explore overweight and obesity diagnosed. National Heart, Lung, and Blood Institute website. Available at: Updated July 13, 2012. Accessed February 27, 2014.

  • Heart-Health Risk Assessment. American Heart Association website. Available at: Updated November 13, 2013. Accessed February 27, 2014.

  • Obesity in adults. EBSCO DynaMed Plus website. Available at: Updated July 10, 2016. Accessed October 6, 2016.

  • Obesity in children and adolescents. EBSCO DynaMed Plus website. Updated July 10, 2016. Accessed October 6, 2016.