Correction of self-reported BMI based on objective measurements: a Belgian experience

Area of Science:

• Public Health
• Epidemiology
• Biostatistics

Background:

• Obesity is a growing public health concern in Belgium.
• Self-reported body mass index (BMI) can be biased and lead to underestimation.
• Accurate monitoring of obesity requires reliable BMI data.

Purpose of the Study:

• To assess the bias in self-reported BMI using data from the Belgian Food Consumption Survey (FCS).
• To develop correction factors to adjust self-reported BMI for more accurate obesity prevalence estimates.
• To re-evaluate obesity prevalence in Belgium using adjusted BMI data.

Main Methods:

• Cross-sectional analysis of data from the Health Interview Survey (HIS) and FCS.
• Comparison of measured and self-reported BMI in the FCS to identify misreporting.
• Calculation of correction factors based on demographic variables (region, gender, education, age).
• Application of correction factors to HIS data to derive a corrected BMI classification.

Main Results:

• Self-reported BMI in the FCS was underestimated by a mean of 0.97 kg/m² compared to measured BMI.
• 28% of individuals classified as obese underestimated their BMI.
• Adjusting HIS data with correction factors increased the obesity prevalence from 13% to 17%, approximating measured values.

Conclusions:

• Self-reported BMI consistently underestimates obesity prevalence.
• Adjustment of self-reported BMI is crucial for obtaining accurate obesity estimates.
• Accurate obesity data derived from adjusted BMI are essential for effective public health decision-making.