220073 Comparison of Body Mass Index and Percent Body Fat Measurements used to Assess Obesity for Participants in Health Fairs

Tuesday, November 9, 2010

William Moore, PhD Epidemiology , Department of Biostatistics and Epidemiology, University of Oklahoma Prevention Research Center, Oklahoma City, OK
Patrick Champion, MS Mathematics , Insight Global, Inc, Atlanta, GA
June E. Eichner, PhD , Department of Biostatistics and Epidemiology, University of Oklahoma Prevention Research Center, Oklahoma City, OK
Introduction: Bioelectric impedance analysis (BIA) using footpad style electrodes and body mass index (BMI) are convenient methods to estimate weight status in large populations. In particular, BMI has been used to assess obesity prevalence and trends nationally. However, BMI is an imprecise method to assess true adiposity. This study evaluated the concordance between the two methods and evaluated optimal BMI cut-points for better agreement with BIA estimated adiposity.

Methods: Physical and demographic data on 249 adults were collected during several health fairs in Oklahoma in 2005 and 2006. Percent body fat was measured by BIA. The weighted kappa statistic was used to test for agreement in categorizing body composition between BMI and by BIA. Receiver operating characteristic curves were used to evaluate the optimal BMI cut-point value for obesity based on percent body fat estimates from BIA.

Results: Prevalence rates of overweight and obesity were similar to the National Health and Nutrition Examination Survey (66.7% vs. 66.3%) based on BMI. The kappa statistic was higher for women than for men (0.84 vs. 0.69). The BMI cut-points with minimum misclassifications of obesity for men, women, and overall was 29 (sensitivity 0.84, specificity 0.85), 28 (sensitivity 0.93, specificity 0.88), and 29 (sensitivity 0.86, specificity 0.89) respectively. The standard BMI for obesity nationally is 30.

Conclusions: There is substantial agreement between BMI and BIA for the categorization of obesity. However, lower BMI cut-points provide better agreement with BIA estimates of obesity.

Learning Areas:
Public health or related research

Learning Objectives:
Compare the assessment of adiposity using body mass index and bioelectrical impedance.

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I am qualified to present because I provided sensitivity, specificity, and ROC curve analysis of the data and wrote portions of the abstract.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.