Development and validation of skinfold-thickness prediction equations with a 4-compartment model

Development and validation of skinfold-thickness prediction equations with a 4-compartment model1–3 Matthew J Peterson, Stefan A Czerwinski, and Roger M Siervogel ABSTRACT Background: Skinfold-thickness measurements are commonly obtained for the indirect assessment of body composition. Objective: We developed new skinfold-thickness equations by using a 4-compartment model as the reference. Additionally, we compared our new equations with the Durnin and Womersley and Jackson and Pollock skinfold-thickness equations to evaluate each equation’s validity and precision. Design: Data from 681 healthy, white adults were used. Percentage body fat (%BF) values were calculated by using the 4-compartment model. The cohort was then divided into validation and crossvalidation groups. Equations were developed by using regression analyses and the 4-compartment model. All equations were then tested by using the cross-validation group. Tests for accuracy included mean differences, R2, and Bland-Altman plots. Precision was evaluated by comparing root mean squared errors. Results: Our new equations’ estimated means for %BF in men and women (22.7% and 32.6%, respectively) were closest to the corresponding 4-compartment values (22.8% and 32.8%). The Durnin and Womersley equation means in men and women (20.0% and 31.0%, respectively) and the Jackson and Pollock mean in women (26.2%) underestimated %BF. All equations showed a tendency toward underestimation in subjects with higher %BF. Bland-Altman plots showed limited agreement between Durnin and Wormersley, Jackson and Pollock, and the 4-compartment model. Precision was similar among all the equations. Conclusions: We developed accurate and precise skinfold-thickness equations by using a 4-compartment model as the method of reference. Additionally, we found that the skinfold-thickness equations frequently used by clinicians and practitioners underestimate %BF. Am J Clin Nutr 2003;77:1186–91. KEY WORDS Body composition, skinfold thickness, body compartments, anthropometry, adipose tissue, nutritional assessment, body fat, obesity INTRODUCTION Higher amounts of body fat and obesity are associated with increased risks of adverse health events and greater mortality (1, 2). Skinfold thicknesses are commonly measured in clinical and field settings for the assessment of percentage body fat (%BF) because this method is simple to perform and low in cost (3). Two of the most widely used skinfold-thickness equations are those developed by Durnin and Womersley and Jackson and Pollock (4–6). 1186 The Durnin and Wormersley equation and the Jackson and Pollock equation were developed and validated by using a 2-compartment (2C) model. The 2C model separates the composition of the body into fat mass and fat-free mass. Using Siri’s equation (7), the 2C model is written as: %BF = [(4.95/BD)  4.5]  100 (1) where BD is whole-body density in g/cc. Use of the 2C-model equation requires the assumptions that body hydration level and bone mineral content are both stable. Unfortunately, these assumptions are often violated because of significant variations in hydration levels and mineral contents between ages, sexes, and races (8–10). The inability of the 2C model to detect these differences can lead to potentially large errors in estimates of %BF in persons for whom these assumptions are violated. Thus, use of the 2C model for development and validation of skinfold-thickness prediction equations is less than ideal (10–14). Recent advances in in vivo measurement, including 4-compartment (4C) body composition assessment, have allowed researchers to assess variations in hydration levels and bone mineral contents that hydrodensitometry alone cannot measure (13). The 4 compartments of the 4C model are fat, mineral, water, and residual. By adding measurements of total body water (TBW), bone mineral density [via dual-energy X-ray absorptiometry (DXA)], and BD (via hydrodensitometry), it is possible to measure individual variances in mineral and water, thus, in theory, leading to more accurate measurement of %BF. It has been theorized that multiple measures could lead to the propagation of additive errors when using the 4C model, however, researchers have shown negligible additive errors with this model (11). In addition, the 4C model has been used as the criterion method in studies with children, younger and middle-aged adults, and the elderly (3, 10, 11, 15–18). 1 From the VA Medical Center, Geriatric Research, Education and Clinical Center, Durham, NC (MJP); Wright State University School of Medicine, Lifespan Health Research Center, Kettering, OH (SAC and RMS); and the Center for the Study of Aging and Human Development, Duke University Medical Center, Durham, NC (MJP). 2 Supported by the National Institutes of Health, National Institute of Child Health and Human Development, grant no. R01HD12252. 3 Address reprint requests to MJ Peterson, Durham VAMC (182), Geriatric Research, Education and Clinical Center, 508 Fulton Street, Durham, NC 27705. E-mail: . Received May 7, 2002. Accepted for publication October 24, 2002. Am J Clin Nutr 2003;77:1186–91. Printed in USA. © 2003 American Society for Clinical Nutrition SKINFOLD-THICKNESS PREDICTION EQUATIONS We developed a new skinfold-thickness equation (%BFnew) to predict %BF by using the 4C model as the reference in younger and middle-aged adults (18–55 y). We evaluated the performance of %BFnew compared with %BF estimates derived from 2 commonly used skinfold-thickness equations, namely those of Durnin and Wormersley (%BFDW) and Jackson and Pollock (%BF JP). Because technology that allows us to use a 4C model for validation studies is now accessible, we decided it was important to examine the possibility of providing clinicians and practitioners with improved skinfold-thickness prediction equations. SUBJECTS AND METHODS Subjects The subjects in the present study are a subset of the participants in the Fels Longitudinal Study. They were enrolled in the Fels Longitudinal Study between 1929 and the present, typically soon after their birth. Most of the Fels participants are white, resided in southwestern Ohio at the time of their enrollment, and were selected for enrollment because their parents were willing to allow them to participate in a long-term, serial study. To date, there have been > 1200 participants in the study; they are examined at regular intervals throughout their life span. Of these 1200, a total of 900 are participating in the currently funded National Institutes of Health study. All subjects provided written informed consent. The Fels Longitudinal Study and its participants have been described in detail previously (19). The standard body-composition exam consists of the anthropometric assessment of weight, stature, and several skinfold thicknesses (chest and abdomen skinfold thicknesses are not currently measured). Many other measures of body composition, including DXA, hydrodensitometry, and b (...truncated)