Adiposity is often approximated by body mass index (BMI) in population studies based on self-reported weight and height (kg/m(2)). However, self-reports tend to underestimate weight and overestimate height, leading to an underestimation of BMI and the prevalence of overweight and obesity. We examined a subgroup of the Multiethnic Cohort Study participants to determine how well self-reported and measured anthropometry correlate with each other, overall and by race/ethnicity, total and abdominal adiposity level, and amount of adulthood weight gain. A cross-sectional sample of 30 Caucasian and 30 Japanese American female cohort participants, between ages 60-65, was selected in such a way the two groups had a similar BMI distribution across the range (18.5-40 kg/m(2)). Subjects first reported their weight, height, and waist and hip circumferences at home and within several days underwent objective measurements by trained staff and also a whole-body scan of dual energy X-ray absorptiometry (DXA) at a study clinic. The women under-reported their weight by 0.93 kg, waist circumference by 3.95 cm and hip circumference by 0.10 cm and over-reported their height by 0.85 cm. This led to an under-estimation of BMI by 0.67 kg/m(2) and waist/hip ratio by 0.04. The effect of misreporting (self-report minus measurement) on BMI and waist/hip ratio was significantly greater in higher BMI groups (p-heterogeneity = 0.007 for BMI, 0.0005 for waist/hip ratio), among women with central obesity (waist circumference > 88 cm; p-heterogeneity = 0.006, 0.01) and among women who had gained higher amounts of weight since age 21 (p-heterogeneity = 0.03, 0.01) compared to their counterparts. A similar trend of greater self-report bias was found among women with higher levels of DXA-based total and abdominal adiposity. We did not observe any heterogeneity in these findings by ethnicity. Our results confirm that a small degree of under-reporting exists in self-reported BMI and waist/hip ratio values, and it tends to increase in women with a larger current body size or history of greater weight gain. Studies are underway to investigate this question in greater depth in men and women from five race/ethnic groups.
Keywords: anthropometry; central obesity; obesity; race/ethnicity; self-report.