How do you measure obesity and overweight in children under 2 years old according to official guidelines from the Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), or American Academy of Pediatrics (AAP)?

Measuring Obesity and Overweight in Children Under 2 Years According to Official Guidelines

For children under 2 years of age, the World Health Organization (WHO) growth charts should be used to assess weight status, with high weight-for-length defined as ≥97.7th percentile (labeled as the 98th percentile on the charts) to identify overweight and obesity. 1, 2

WHO vs CDC Growth Charts for Children Under 2 Years

The CDC and WHO both recommend using WHO growth charts for all children under 24 months of age, regardless of feeding method 1, 2. This recommendation is based on several important factors:

• The WHO charts reflect growth patterns among children who were predominantly breastfed for at least 4 months
• The WHO charts are based on a more internationally representative sample of healthy children
• The WHO charts better represent how children should grow in an ideal environment 1

Specific Parameters for Measuring Overweight in Children <2 Years

When using WHO growth charts for children under 2 years:

• Weight-for-length is the primary parameter used to assess overweight status
• The 97.7th percentile (labeled as the 98th percentile on charts) is the recommended cutoff for identifying high weight-for-length 1
• BMI-for-age is also available on WHO charts but is not interchangeable with weight-for-length 3

Interpreting WHO Growth Charts for Overweight Assessment

When interpreting WHO growth charts for overweight assessment:

• Children with weight-for-length ≥97.7th percentile are considered to have high weight-for-length (equivalent to overweight/obesity)
• The WHO charts identify more children as at risk for overweight/obesity compared to CDC charts (21.0% vs 16.6% using the respective cutoffs) 3
• Early identification of high weight-for-length is important as it strongly predicts obesity at age 5 years 4

Clinical Application and Monitoring

For clinical application:

• Plot measurements on the appropriate WHO chart at each well-child visit
• Monitor for concerning growth patterns, particularly crossing two or more major percentile lines upward 2
• Formula-fed infants tend to gain weight more rapidly after approximately 3 months and may cross upward in percentiles 1
• Early recognition of a tendency toward obesity might appropriately trigger interventions to slow the rate of weight gain 1

Important Considerations and Pitfalls

Several important considerations should be noted:

• At age 24 months, transition from WHO to CDC growth charts occurs 1, 2
• Length measurements switch from recumbent to stature measurements at age 2 years, with measurements of length being approximately 0.7-0.8 cm greater than stature measurements 1
• The WHO BMI-for-age and weight-for-length percentiles are highly correlated (r²=0.83) but not interchangeable, especially in children ≤6 months 3
• For approximately 9% of all children under 2, BMI-for-age and weight-for-length percentiles differ by >25 percentile points 3

By following these guidelines and understanding the nuances of growth assessment in young children, clinicians can appropriately identify and address concerns about overweight and obesity in children under 2 years of age.