Accuracy of self-reported BMI using objective measurement in high school students

Area of Science:

• Public Health
• Adolescent Health
• Biostatistics

Background:

• Self-reported body mass index (BMI) is a common research limitation, particularly in adolescents.
• Existing research on the accuracy of adolescent self-reported BMI is mixed.
• Accurate BMI measurement is crucial for health interventions and research outcomes.

Purpose of the Study:

• To assess the accuracy of self-reported BMI against measured BMI in U.S. adolescents.
• To investigate potential gender differences in self-reported BMI accuracy.
• To evaluate the reliability of BMI categorization based on self-reported data.

Main Methods:

• Cross-sectional study involving 425 adolescents from five high schools across four U.S. states.
• Collected self-reported and objectively measured height and weight data.
• Calculated BMI and categorized it (underweight, normal, overweight, obese) using CDC criteria; analyzed using Limits of Agreement (LOA) and Kappa statistic (Κ).

Main Results:

• Adolescents underreported weight and overreported height, leading to fair agreement for continuous BMI (LOA).
• Substantial agreement was found for BMI categorization (Κ=0.71).
• Higher BMI correlated with greater inaccuracies; specificity for obesity was low (50.0%).

Conclusions:

• Self-reported BMI categorization is more accurate than continuous self-reported BMI values in adolescents.
• Findings support using categorized self-reported BMI in health-related interventions.
• Awareness of systematic biases (under/overreporting) is essential when using self-reported adolescent BMI data.