Physiology, Body Mass Index

Excerpt

Body mass index (BMI) is the method of utilizing an adult's height and weight to broadly place them into underweight, normal weight, overweight and obese categories. An individual's BMI is important in the determination of potential future health issues and has been widely used as a factor in the determination of various public health policies. BMI can be calculated using metric or imperial (US) units.

Metric units: weight (kilograms) divided by height squared (meters)

1. BMI = kg/m²

Imperial (US) units: weight (pounds) divided by height squared (inches) multiplied by 703

1. BMI = 703 (lbs/in²)

To further discuss BMI and the issues, disease states, and clinical significance, it is important to understand the current cut-off points of each category as determined by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC).

World Health Organization

1. Severely Underweight: <16 kg/m²

2. Underweight: 16.0 to 18.4 kg/m²

3. Normal weight: 18.5 to 24.9 kg/m²

4. Overweight: 25.0 to 29.9 kg/m²

5. Moderately Obese: 30.0 to 34.9 kg/m²

6. Severely Obese: 35.0 to 39.9 kg/m²

7. Morbidly Obese: ≥40.0 kg/m²

Centers for Disease Control and Prevention

1. Underweight: less than or equal to 18.4 kg/m²

2. Normal weight: 18.5 to 24.9 kg/m²

3. Overweight: 25.0 to 39.9 kg/m²

4. Obese: ≥40.0 kg/m²

Centers for Disease Control and Prevention Child and Teen BMI (Utilized for those aged 2 to 20)

1. Underweight: below the 5th percentile

2. Healthy weight: between the 5th and 85th percentile

3. Overweight: between the 85th and 95th percentile

4. Obese: greater than or equal to the 95th percentile

World Health Organization Asian-Population Criteria:

1. Underweight: <18.5 kg/m²

2. Normal weight: 18.5 to 23.0 kg/m²

3. Overweight: 23.0 to 27.5 kg/m²

4. Obese: ≥27.5 kg/m²