Child Body Mass Index

Body mass index or BMI has become a household term for adults across the globe. With the rise in the number of overweight children, more and more people are taking interest in the weight management of their kids. Usage of BMI for kids has improved significantly in recent years. Even though, the BMI in kids is calculated using the same formula as in adults, unlike the latter, the BMI charts for children are based on their age and gender. In adults, the same chart applies for all, whereas in kids, it differs for boys and girls and for various age groups.

How is BMI Calculated in Kids?

Weight classification in kids depends on their age and gender. The BMI is calculated by dividing the body weight in kilograms with the square of the height in meters. The resultant value is the BMI, which can be correlated to body fatness in children. It is very important to obtain the accurate height and weight of a child in order to calculate the BMI. The BMI of any child can be evaluated on the basis of 'BMI-for-age percentile'. Percentile is the value below which a certain percent of observations fall. For example, if a child belongs to the 75th percentile, as per his / her age, gender and BMI, it means that 75% of kids of the same age and gender have a lower BMI than the said child.

The percentile is interpreted on the basis of the age and gender of the kids. This criteria of classification is based on the fact that the amount of body fat changes with age and gender. Hence, the BMI of kids is often referred to as BMI-for-age. Many organizations have developed specialized charts for this purpose an example being the one developed by the Centers for Disease Control and Prevention. The percentile for a particular BMI is calculated as per the chart and the weight status is determined according to the category of percentile. The categories are as follows:

• If the corresponding value of the BMI in the chart is below the 5th percentile, your child is considered as underweight.
• If it comes between 5th to 85th percentile, the weight of your child is normal for his / her age.
• 85th to 95th percentile shows a risk of overweight.
A percentile which is equal to or above 95 indicates overweight.

This criteria is applicable for kids (as well as teens) in the age group 2 to 19 and is helpful in determining their weight status. If your kid is overweight or obese, you can go for further tests to determine and control the fat content in his / her body.

The third category, which discusses the 'risk of overweight' is found to be confusing for many people. As per some charts, the third category is classified as overweight and the fourth as obese, but many others omit the word 'obese', not to hurt the feelings of children. Hence, the third category should be understood as 'being on the verge of overweight' or 'overweight' itself and the fourth category, which is classified as 'overweight' is actually equivalent to 'obesity'.

It can always happen that kids, who look like being overweight, may not be like that as per the BMI-for-age percentile and vice versa. This chart is considered as a reliable tool to determine the weight status of kids as well as teens.