Development and validation of skinfold-thickness equations for predicting body fatness in Ethiopian adults

OBJECTIVES: Both body fat and lean body mass have important roles in health and wellbeing. It is crucial that researchers and clinicians can accurately measure them, especially in nutritionally vulnerable populations such as people living in rural areas of Ethiopia. Skinfold thickness measurements are one of the few methods to measure % body fat outside of a clinical setting. The validity of the measurements is dependent upon age, sex, and ethnicity. The existing skinfold thickness equations are derived from populations of European descent. This study will demonstrate that existing equations are not valid for Ethiopian adults and create new, sex-specific equations for this population. METHODS: Skinfold thickness will be measured on 250 adults recruited from Jimma City, Ethiopia. Percent body fat will be calculated using several existing skinfold thickness equations. For women, the equations are the Sloan; Jackson, Pollock, & Ward; and Durnin and Wormsley. The equations for men are Sloan; Jackson and Pollock; and Durnin and Wormsley. The results of these equations will then be compared against % body fat measured by a BodPod. Pearson's correlation coefficient and Bland-Altman plots will be used to assess the validity of each calculation. Stepwise forward regression will be used to determine new sex-specific equations. RESULTS: In women, the Sloan equation had moderate correlation (0.59) while Jackson, Pollack, and Ward and the Durnin and Wormsley equations had near-perfect correlation (0.81 and 0.88 respectively). In men, the Sloan equation had substantial correlation (0.79) while the Jackson and Pollack and the Durnin and Wormsley had near-perfect correlation (0.89 and 0.85 respectively). Scatter and Bland Altman plots showed that all equations underestimated the % body fat measured compared to a BodPod requiring new equations. For women: body density = 1.068892 − 0.00088 x −0.0005412 y − 0.0012765 z. Where x is the skinfold thickness at the suprailiac crest, y is thigh, and x is subscapular. For men: body density = 1.08899 −0.0014585 m −0.0008318 n. Where m is abdominal skinfold thickness and n is thigh skinfold thickness. CONCLUSIONS: The current most commonly used skinfold thickness equations are not valid for use in Ethiopian adults. The equations put forth in this analysis should be used for this population. FUNDING SOURCES: H.E. Babcock Fund, NIDDK/NIH.