BMI for Children and Teens: Percentiles and Reference Values

How is BMI calculated in children?

The formula is the same as in adults: weight (kg) divided by height squared (m²). However, the interpretation is completely different. In children and adolescents aged 2 to 18, BMI is compared to that of other children of the same age and sex, expressed as a percentile.

This is because healthy BMI varies significantly during growth: a BMI of 17 may be normal for a 5-year-old child but low for a 15-year-old.

Why is BMI in children different?

Children grow at different speeds and their body composition changes constantly. What is normal for a 7-year-old child is completely different from what is normal for a 15-year-old teenager. That is why age-specific reference tables by sex are needed.

Warning signs in children

• Percentile below 5: consult the pediatrician, may indicate insufficient nutrition
• Percentile above 95: talk with the pediatrician about eating habits and physical activity
• Sudden percentile change (moving more than 2 categories up or down in a short time)
• BMI that does not rise even though the child is growing taller (sign of insufficient nutrition)

Recommendations for a healthy BMI in children

• At least 60 minutes of moderate or intense physical activity per day
• Limit screens to less than 2 hours a day outside school hours
• 5 servings of fruits and vegetables per day
• Reduce added sugars and ultra-processed foods
• Annual pediatric check-up with weight, height, and BMI measurement

Important: never put a child on a diet without medical supervision. Children need sufficient nutrients for their development.

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