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Body mass index or BMI (wt/ht2) is measure of body fat based on height and weight that applies to both adult men and women. For adults over 20 years old, BMI falls into one of these categories:
BMI |
Weight Status |
Below 18.5 |
Underweight |
| 18.5 – 24.9 |
Normal |
25.0 – 29.9 |
Overweight |
30.0 and Above |
Obese |
The BMI ranges are based on the effect body weight has on disease. As BMI increases, the risk for some diseases increases. Some common conditions related to overweight and obesity are:
- Cardiovascular disease
- High blood pressure
- Osteoarthritis
- Some cancers
- Diabetes
- Premature death
BMI is only one of the many factors which are used to predict the risk of getting a disease. We have to remember that weight is only one factor that is related to disease.
In children and teens, body mass index is used to assess underweight, overweight, and risk for overweight. Children's body fatness changes over the years as they grow. Also, girls and boys differ in their body fatness as they mature. This is why BMI for children, also referred to as BMI-for-age, is gender and age specific. BMI-for-age is plotted on gender specific growth charts. These charts are used for children and teens 2 – 20 years of age.
Each of the CDC BMI-for-age gender specific charts contains a series of curved lines indicating specific percentiles. Healthcare professionals use the following established percentile cutoff points to identify underweight and overweight in children.
Percentile |
Weight Status |
BMI-for-age < 5th percentile |
Underweight |
| BMI-for-age 85th
percentile |
Overweight |
BMI-for-age > 95th percentile |
Obese |
What does it mean if my child is in the 70th percentile? The 70th percentile means that compared
to children of the same gender and age, 70% have a lower BMI. |
BMI decreases during the preschool years, then increases into adulthood. The percentile curves show this pattern of growth.
Example
Let's look at the BMI for a boy as he grows. While his BMI changes,
he remains at the 95th percentile BMI-for-age.
Age |
BMI |
Percentile |
2 years |
19.3 |
95th |
4 years |
17.8 |
95th |
| 9 years |
21.0 |
95th |
| 13 years |
25.1 |
95th |
We see how the boy's BMI declines during his preschool years and increases as he gets older.
What are the advantages of using BMI-for-age with children from
2 to 20 years?
 |
BMI-for-age
provides a reference for adolescents that can be used
beyond puberty. |
|
BMI in children and adolescents compares well to laboratory measures of body fat. |
|
BMI-for-age can
be used to track body size throughout life. |
|
Children with a BMI-for-age above the 95th percentile are more likely to become overweight adults. |
Content Source: www.cdc.gov
For more information on how to use the growth charts visit
The Growth Chart Training Modules.
For the 2000 CDC Growth Charts and Additional Information visit CDC'S
National Center for Health Statistics