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Diagnosis of Obesity
- BMI in adults:
- Overweight is defined as a body mass index (BMI) greater than or equal to 25.
- Obesity is defined as having a BMI greater than or equal to 30.
- Severe or morbid obesity is defined as having a BMI greater than or equal to 40.
- BMI in children is based on growth charts:
- Overweight is BMI greater than or equal to 85th percentile for gender and age.
- Obesity is BMI greater than or equal to 95th percentile for gender and age.
- Severe obesity is BMI greater than or equal to 99th percentile for gender and age.
- Other methods to diagnose obesity include:
- 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 40 inches (102 centimeters) men or 35 inchess (88 centimeters) 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.
- Reviewer: Michael Woods, MD, FAAP
- Review Date: 02/2017
- Update Date: 02/23/2017