Figures 1, 2, 3 are based on the same regression models and illustrate how age and gender are associated with the discrepancies between measured and self-reported height, weight and BMI. Both men and women overstate their height, particularly at older ages, although the extent of over-reporting is greater for men than for women, p < 0.01 (Figure 1). Men also tend to overstate their weight, although by relatively small amounts (on average, less than 1 kg) (Figure 2). In contrast, women understate their measured weight with the greatest understatement (on average, more than 3 kg) found among young women (Figure 2). The net effect on the BMI of these patterns in self-reporting of height and weight is depicted in Figure 3. Although self-reported BMI understates measured BMI for both men and women across all age groups, the discrepancy is significantly greater (p < 0.001) for women except at the very oldest ages. For both genders, the most accurate BMI values based on self-reported height and weight are obtained between the ages 42 and 55, with larger underestimates of measured BMI among the youngest and oldest individuals.
