When is a Child Overweight?

Let’s define what it means to be overweight in children. Growth charts need to be used; you can’t always tell by looking. Sometimes an overly concerned parent may assess their truly normal-weighted child as being overweight. On the other hand, studies have shown that many parents tend to overlook their child’s obesity.

New growth charts have been released by the Center for Disease Control and you can download the Individual Charts with All Percentiles.

Especially important are the “Body Mass Index for Age” charts for your child’s age group. Body mass index (BMI) has advantages over other methods of monitoring obesity in children and adolescents and the charts can be downloaded for children 2 to 20 years of age. It correlates closer to actual body fat measurements.

How we interpret BMI percentiles for children:

Now look at the Body Mass Index for Age charts for children 2-20 years of age:

For boys 2-20 years of age, BMI for age
For girls 2-20 years of age, BMI for age

Now plot out the calculated number value you found for the BMI for your child and plot that number on the chart for their age. If the point on the chart is at:

BMI-for-age < 5th percentile: Underweight
BMI-for-age 85th percentile to < 95th percentile: At risk of overweight
BMI-for-age ? 95th percentile: Overweight

Understand that some children may fall in the At risk or Overweight category, but due to muscle mass or bone structure, may not really be overweight.  Also a large jump up in the percentile for the BMI may also be a problem.  Please review with your child’s health provider to get accurate interpretation of these numbers.

How we interpret BMI percentiles for adults:

In adults, the numerical calculated value for BMI is interpreted as follows:

BMI Weight Status for Adults
Below 18.5 Underweight 
18.5 – 24.9 Normal 
25.0 – 29.9 Overweight 
30.0 and Above Obese


You can also calculate your BMI maually

English Formula:

BMI = Weight in Pounds_________ x 703 
(Height in inches) x (Height in inches)

Example: A 33 pound child is 37 inches tall
(33 ¸ (37 x 37)) x 703 = (33 ¸ 1369) x 703 = 0.024105 x 703 = 16.9

Metric Formula:

BMI = Weight in Kilograms_____ 
(Height in Meters) x (Height in Meters) 
or 
BMI = Weight in Kilograms x 10,000
(Height in centimeters) x (Height in centimeters) )

Example: A 17 kg child is 106 cm tall (NOTE: 1 meter = 100 cm)
17 kg ¸ (1.06 m x 1.06 m) = 17 ¸1.12 = 15.2

How we interpret BMI percentiles for children:

Now look at the Body Mass Index for Age charts for children 2-20 years of age:

For boys 2-20 years of age, BMI for age
For girls 2-20 years of age, BMI for age

Now plot out the calculated number value you found for the BMI for your child and plot that number on the chart for their age. If the point on the chart is at:

BMI-for-age < 5th percentile: Underweight
BMI-for-age 85th percentile to < 95th percentile: At risk of overweight
BMI-for-age ? 95th percentile: Overweight

Understand that some children may fall in the At risk or Overweight category, but due to muscle mass or bone structure, may not really be overweight.  Also a large jump up in the percentile for the BMI may also be a problem.  Please review with your child’s health provider to get accurate interpretation of these numbers.

How we interpret BMI percentiles for adults:

In adults, the numerical calculated value for BMI is interpreted as follows:

BMI Weight Status for Adults
Below 18.5 Underweight 
18.5 – 24.9 Normal 
25.0 – 29.9 Overweight 
30.0 and Above Obese