Ethnic differences in self-reported and measured obesity

Abstract

As use of self-reported data to classify obesity continues, ethnic differences in reporting errors remain unclear. The objective of this study is to elucidate misreporting disparities between African Americans (AAs) and European Americans (EAs). The Pennington Center Longitudinal Study (PCLS) is an ongoing investigation of environmental, behavioral, and biological factors associated with obesity, diabetes, and other common diseases. Self-reported and measured height and weight were collected during initial screening for eligibility in various studies by telephone and clinic visits. All ethnicity-sex groups (15,656 adults aged 18-65 years, 53% obese, 34% AA, 37% men) misreported heights and weights increasingly as measured values increased (P < 0.0001). More AA vs. EA women (P < 0.001) misreported height and weight, but more EA vs. AA men misreported their weight (P < 0.02). Obesity was underestimated more in AA vs. EA women (self-reported - measured prevalence = -4.0% (AA) vs. -2.6% (EA), P < 0.0001), but less in AA vs. EA men (-3.2% (AA) vs. -4.2% (EA), P < 0.0001)). With measured obesity prevalence equalized at 53% in all groups, the self-reported obesity prevalence in women was 50.4% (AA) vs. 49.6% (EA), and in men 49.8% (AA) vs. 47.3 (EA). Underestimation in women was -2.6% (AA) vs. -3.4% (EA); in men it was -3.2% (AA) vs. -5.7% (EA), P < 0.003. Self-reported height and weight portend underestimation of obesity prevalence and the effect varies by ethnicity and gender. However, comparisons depend on the true prevalence within ethnicity-gender groups. After controlling for obesity prevalence, disparity in underestimation was greater in EA than in AA men (P < 0.003) but not women.

Figure 1

Plot of the differences between self-report and measured (a) height, (b) weight, and (c) BMI against the measured value in a sample of 15,656 African-American and European-American adults from the Pennington Center Longitudinal Study.

Figure 2

Plot of predicted against measured (a) height, (b) weight, and (c) BMI in a sample of 15,656 African-American and European-American adults from the Pennington Center Longitudinal Study. Predicted values were predicted from age, ethnicity, and self-reported values.

Figure 3

Plot of the differences between self-reported and measured prevalences of obesity in the total sample of 15,656 and a random sample of 3,200 African-American (AA) and European-American (EA) adults matched on the distribution of BMI from the Pennington Center Longitudinal Study.