BODY MASS INDEX (BMI)

What is BMI?

BMI, or Body Mass Index, is a simple calculation that uses a child’s height and weight to estimate their body fat. While it’s a helpful tool, it’s not perfect. To get a clearer picture of your child’s health, it’s best to discuss the results with their doctor.

• What it does: Estimates body fat based on height and weight.
• What it doesn’t do: Measure body fat directly. For example, a child with more muscle or a larger frame might have a higher BMI without having excess fat.

How BMI is Tracked

Doctors start checking BMI during routine visits once a child turns 2 years old. Since BMI changes as kids grow, doctors use special growth charts to track progress over time. These charts are specific to a child’s gender and age.

• Why it’s tracked: To monitor if a child is growing at a healthy rate.
• What it shows: Whether a child is gaining weight too slowly or too quickly.

What Do BMI Percentiles Mean?

BMI percentiles compare your child’s BMI to other kids of the same age and gender. For example:

• If your child is in the 60th percentile, it means 60% of kids their age and gender have a lower BMI.

BMI Categories for Kids:

• Underweight: BMI below the 5th percentile.
• Healthy weight: BMI between the 5th and 85th percentiles.
• Overweight: BMI between the 85th and 95th percentiles.
• Obese: BMI at or above the 95th percentile.

Important Note: BMI is just one piece of the puzzle. It’s better to look at trends over time rather than focusing on a single number.

BMI During Puberty

BMI can be less accurate during puberty because kids often grow and gain weight quickly. This is usually normal, but your doctor can help determine if the weight gain is healthy or a cause for concern.

Using the KidsHealth BMI Calculator

The KidsHealth BMI Calculator is designed for children and teens aged 2 to 20. It helps you find your child’s BMI and see how it compares to others of the same age and gender.

How to Use the Calculator:

1. Choose your measurement system (US standard or metric).
2. Select your child’s gender (male or female).
3. Enter your child’s birth date.
4. Input their height and weight.
5. Click “Calculate BMI” to see the results.

Key Takeaways

• BMI is a useful tool but doesn’t tell the whole story about body fat.
• It’s important to track BMI over time rather than focusing on one number.
• If you’re worried about your child’s weight, talk to their doctor for guidance.

By understanding BMI and working with your child’s doctor, you can help ensure they’re growing in a healthy way.