Body Mass Index (BMI) for Children

Obesity is a growing cause of concern for parents all over the world today. A healthy weight during childhood is needed for healthy functioning of the heart and for the prevention of any cardiovascular diseases. Heart disease is not the only risk related to obesity. Obesity can also cause other lifestyle illnesses like Type 2 diabetes, asthma, sleep apnea, and psychological problems owing to the social stigma of appearance.

What is BMI?

Body Mass Index ( BMI) is the weight of the person in kilograms divided by the square of the height measured in metres. For children and teenagers, BMI is age and gender specific and referred to as BMI-for-age. Being overweight and underweight during childhood can pose a risk and can lead to health issues.

How is BMI Calculated for Kids?

Body Mass Index is a calculation of a child’s weight in relation to their height to assess body fat and diagnose any potential weight-related issues. Calculating the BMI for children involves tracking the BMI to other children of the same gender and age in charts to present a detailed picture over a period of time. A smooth curve reflects healthy growth. Track the progress but make sure to consult your doctor to take regular BMI measurements. Once you finish calculating, use the BMI chart for children to track the progress.

BMI-for-age and Growth chart for girls :

Source: https://www.cdc.gov/growthcharts/data/set1clinical/cj41l024.pdf

BMI-for-age and Growth chart for boys :

Source: https://www.cdc.gov/healthyweight/assessing/bmi/childrens_bmi/about_childrens_bmi.html

How to Track your Child’s BMI?

Your doctor will determine routine BMI check-ups starting from when your child is 2 years old. These measurements will be plotted on a chart to compare them with kids of the same sex and age. Doctors plot BMI’s of kids on standard growth charts, separate ones for boys and girls. This helps to account for differences in growth rates and amount of body fat as age matures.

Information recorded on your child’s medical record will be monitored and tracked to see the progress over several visits. This information helps to identify kids and adolescents at risk of being overweight as they grow older. By closely monitoring these kids, doctors can take the required action needed to prevent any issues that may arise in future.

What is BMI Percentile and How Should it Be Interpreted?

BMI calculated for children and teens is expressed as a percentile, plotted on the growth charts to obtain a percentile ranking. Percentiles are commonly used as an indicator to assess the size and growth patterns of children. The percentile is a comparative yardstick to other kids of the same age and sex. Weight and height change during growth and development so does their relation to body fat.

What is Normal BMI for Children?

BMI numbers for different ages and genders have different interpretations. A comparison with other children is mandatory as children develop muscles with age and boys tend to have more muscle than girls. A healthy BMI for children in percentile lies between the 5th percentile and the 85th percentile. Normal child BMI range for boy’s ranges from 13.8-16.8 for a 5-year-old, 14.2 – 19.4 for a 10-year-old and 6.5-23.4 for a 15-year-old. Normal BMI range for girls ranges from 13.6- 16.7 for a 5-year-old, 14 – 19.5 for a 10-year-old and 16.3 – 24 for a 15-year-old.

How is BMI Used for Kids?

BMI is not a diagnostic tool for kids but a screening measure for any weight-related issues. If a child’s graph indicates a high BMI, doctors will recommend further direct measure like skinfold thickness measurements, diet evaluations and other health screening to determine if excess fat is a problem.

Is BMI Interpreted the Same Way for Children as it is for Adults?

Although BMI is calculated on the basis of weight and height, and their relation to body fat, it needs to be expressed in relation to other children of the same sex and age. With children, it needs to be done on a comparative basis as children develop and mature with age. For adults, BMI is interpreted as weight status categories which are independent of sex and age.

Weight Categories for Kids

As soon as a child’s BMI is ascertained, it can be seen where it falls within the expected range. The weight categories are mentioned below:

• Underweight – A category where the BMI is less than the 5^th percentile.
• Normal Weight – A category where the BMI is between the 5^th percentiles to the 85^th percentile.
• Over Weight – A category where the BMI is more than the 85^th percentile to below the 95^th percentile.
• Obese – A category where the BMI is greater than or equal to the 95^th percentile.

Health Risks of Having a High and Low BMI Percentile

Risks associated with obesity

• High blood pressure
• High Cholesterol
• Type 2 diabetes
• Sleep apnea and asthma
• Liver diseases
• Problems in joints and muscles
• Stress, depression and other behavioural problems owing to low self-esteem

Risks associated with being underweight:

• Respiratory disorders
• Weak Immune system
• Prone to injuries
• Nutritional deficiencies

BMI cannot be used to diagnose a health issue but is an effective screening tool to delve deeper to probe any underlying issues. It provides a glimpse to determine any weight-related issues that a child may have or could be prone to in the future.