Body mass index (BMI)

A measure of weight in kilograms (kg) relative to height in meters squared (m2). BMI is considered a reasonably reliable indicator of total body fat, which is related to the risk of disease and death. BMI status categories include underweight, healthy weight, overweight, and obese (See Table).

Overweight and obese describe ranges of weight that are greater than what is considered healthy for a given height, while underweight describes a weight that is lower than what is considered healthy. Because children and adolescents are growing, their BMI is plotted on growth charts for sex and age. The percentile indicates the relative position of the child’s BMI among children of the same sex and age.

BMI is a measure of body weight relative to height. The BMI tool uses a formula that produces a score often used to determine if a person is underweight, at a normal weight, overweight, or obese. For adults, a BMI of 18.5 to 24.9 is considered healthy (or "normal"). A person with a BMI of 25 to 29.9 is considered overweight, and a person with a BMI of 30 or more is considered obese.

Children grow at different rates at different times, so it is not always easy to tell if a child is overweight. BMI charts for children compare their height and weight to other children of their same sex and age. For children ages 2 to19, those who are at or above the 85th percentile are considered overweight. Those who are at or above the 95th percentile are considered obese.

To calculate BMI visit http://nccd.cdc.gov/dnpabmi/Calculator.aspx  for children and http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm  for adults.