Figure 1. Measured (National Health and Nutrition Examination Survey [NAHNES]) and self-reported (NHANES in-person and Behavioral Risk Factor Surveillance System [BRFSS] telephone) BMI by age and sex. Each data point shows the 95% confidence interval (CI) for estimated body mass index as two horizontal lines. When the 95% CI is small, the two horizontal lines appear to overlap. This is particularly the case for BRFSS (shown in red), which has very large sample size. For each survey, a local (non-parametric) regression was used to estimate the age pattern, shown as solid lines.