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. According to the American Heart Association, obesity can also cause other lifestyle illnesses like Type 2 diabetes, asthma, sleep apnea, and psychological problems owing to the social stigma of appearance (1). Therefore, it is very important to keep the BMI of children in check. There are several percentiles of BMI for kids of different ages. You can check which BMI percentile is ideal for your children, observe, and take action accordingly.

What Is BMI?

Body Mass Index (BMI) is the measure of the weight of the person in kilograms divided by the square of the height measured in metres. The calculation helps doctors determine whether the child is healthy, underweight, or overweight (2). 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 of 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 to track children’s progress. How to calculate BMI for kids? It’s quite easy. Follow the below table.

Source: American Academy of Paediatrics (2)

Below is the BMI chart for kids, provided separately for the girl child and the boy child.

BMI-for-age and Growth Chart for Girls

Source: CDC (3)

BMI-for-age and Growth Chart for Boys

Source: CDC (4)

You can also look at the Revised IAP growth charts and Body Mass Index (BMI) for 5 to 18-year-old Indian children here at the Indian Paediatrics website (5). Here, the BMI chart for children by age is presented for easy understanding.

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 BMIs of kids on standard growth charts, separate ones for boys and girls. This helps to account for differences in growth rates and the amount of body fat as age matures.

The 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 per centile, 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, and 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 the 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. So, what is the healthy BMI for kids? Let’s learn.

As per the CDC, BMI percentiles are divided into distinct weight categories (6):

• Below 5th Percentile >> Underweight
• 5th to 85th Percentile >> Healthy Weight
• 85th to 95th Percentile >> Overweight
• Above 95th Percentile >> Obese

How Is BMI Used for Kids?

BMI is not a diagnostic tool for kids but a screening measure for any weight-related issues. Suppose a child’s graph indicates a high BMI. In that case, doctors will recommend further direct measures 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 based on 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. It needs to be done on a comparative basis with children as they develop and mature with age. For adults, BMI is interpreted as a category of weight status that is independent of sex and age. The BMI calculator for children and teenagers should not be used for children aged 18 years and above. There are different calculators for adults and children to measure the BMI (7) (1).

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 percentile to the 85^th percentile.
• Overweight – 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

There are several health problems in a child if the BMI is not in check. Some of the health issues children could face in case of overweight and underweight are (1):

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

FAQs

1. How can I ensure a healthy BMI for my child?

As parents, you should always ensure that your child receives the necessary nutrients from their meals rather than supplements, which should include leafy green vegetables and rich-protein sources like eggs and lean meat, and hydration and minerals from fruits. Additionally, it is also important to reduce giving them highly processed or sugary items as snacks. Add at least one hour of physical activity to their daily routine.

2. How to reduce weight in overweight children?

The first and foremost thing to remember while controlling overweight children’s weight is that you must NOT cut off their diet altogether. You need to reduce their portion slightly. For example, instead of 10 crackers, give them seven or eight. Focus on hydration more. Additionally, do not reward them with food. Many children also do not release when they are full. Teach them signs to notice when the tummy has had enough.

3. What do I do in case of an underweight child?

Cleveland Clinic suggests adding nut butter with fruits and vegetables like peanut butter with apple sticks, starchy foods like potatoes, and heart-healthy oils like olive oil to an underweight child’s diet (8). You can also include high-calories drinks and meals like milkshakes or smoothies, porridge with milk, cheese, yoghurts; sandwiches, etc., as per the NHS (9).

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.

References/Resources:

1. Body Mass Index in Children; American Heart Association; https://www.heart.org/en/healthy-living/healthy-eating/losing-weight/bmi-in-children

2. Body-Mass Index (BMI) in Children; American Academy of Pediatrics; https://www.healthychildren.org/English/health-issues/conditions/obesity/Pages/Body-Mass-Index-Formula.aspx

3. 2 to 20 years: Girls, Body mass index-for-age percentiles; CDC; https://www.cdc.gov/growthcharts/data/set1clinical/cj41l024.pdf; May 2000

4. About Child & Teen BMI; CDC; https://www.cdc.gov/healthyweight/assessing/bmi/childrens_bmi/about_childrens_bmi.html

5. Khadilkar. V, Yadav. S, Agrawal. K. K, etc.; Revised IAP Growth Charts for Height, Weight and Body Mass Index for 5- to 18-year-old Indian Children; Indian Pediatrics; https://indianpediatrics.net/jan2015/jan-47-55.htm

6. BMI Percentile Calculator for Child and Teen; CDC; https://www.cdc.gov/healthyweight/bmi/calculator.html

7. Calculate your body mass index (BMI) for children and teenagers; NHS; https://www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/calculate-bmi-for-children-teenagers/

8. A Dietitian’s Best Advice If Your Child Is Underweight; Cleveland Clinic; https://health.clevelandclinic.org/dietitians-best-advice-child-underweight; September 2020

9. How to help your child gain weight; NHS; https://www.nhs.uk/live-well/healthy-weight/childrens-weight/how-to-help-your-child-gain-weight/

Also Read:

How to Lose Weight for Kids
How to Increase Height in Kids?
How to Calculate Height in Children?
Best Foods to Increase Height in Children
Healthy Foods for Brain Development in Kids