Reliability and Intermethod Agreement for Body Fat Assessment Among Two Field and Two Laboratory Methods in Adolescents
Vincente-Rodrigues G, Rey-Lopez JP, Mesana MI, Poortvliet E, Ortega FB, Polito A, Nagy E, Widhalm K, Sjostrom M, Moreno LA. Obesity. 2011 August; [Epub Ahead of Print]
Body composition can be tested in several different ways: 1) skinfold measurements, 2) bioelectrical impedance, 3) air-displacement plethysmography (Bod-Pod), 4) dual-energy X-ray absorptiometry (DXA), and 5) hydrodensitometry (the current “gold standard”). The method used can be based on many factors including clinician experience, financial feasibility, patient availability, and access to specific facilities. Unfortunately, very few studies have evaluated the reliability of these measurements among children and adolescents. Therefore, Vincente-Rodriguez and colleagues set out to test the day-to-day variability as well as intra- and inter-rater reliability of skinfold measurements, bioelectrical impedance, Bod-Pod, and DXA. Furthermore they tested the degree of agreement for body fat mass (% body fat) using all 4 methods in European adolescents. A total of 84 adolescents (ages 13 to 17 years old) participated in the 2 day study in both Stockholm and Zaragoza, Sweden (DXA was only assessed on 54 participants). On the first day, one trained rater repeatedly measured body fat mass with Bod-Pod (performed 3 times), DXA (performed twice), bioelectrical impedance (performed 3 times), and skinfold caliper measurements (performed 3 times). All measurements were calibrated and measured using the standard factory instructions. Skin fold caliper measurements were taken at 6 measurement sites (triceps, biceps, subscapular, suprailiac, thigh, and calf). On day 2, all 4 methods were measured by the same rater and an additional independent rater. Overall, Bod-Pod, DXA, bioelectrical impedance, and skinfold measurements were reliable and consistent for % body fat when repeated assessments were performed within the same day by the same or different raters or in consecutive days by the same rater. Bod-Pod showed close agreement with bioelectrical impedance and DXA had close agreement with anthropometry. Higher % body fat were recorded using Bod-Pod and bioelectrical impedance compared to DXA and skin fold caliper.
This study presents a very interesting case for the use of all 4 methods of %BF. While each method has its advantages clinicians must be understand the importance of being well trained with whatever method they choose. In most clinical settings, skinfold calipers will be the most widely available and easily administered method. As seen in the results of this study, in the hands of a well-trained rater, this method can show a high agreement with DXA. This data may not be applicable though among clinicians with less experience and training performing skinfold measurements. It is unclear why two methods generated higher % body fat measures than the other two methods. As clinicians, when do you assess % BF and how? It would also be quite interesting to hear if anyone has used the DXA method. If you have, how did you find it? Did it seem worth the costs and travel to a facility?
Written by: Kyle Harris
Reviewed by: Jeffrey Driban
It is very apparent that the rise of childhood obesity needs to be dealt with to help prevent the onset of many chronic diseases in the future or even preventing the rise in type two diabetes in the present. However, it may be unwise to use clinical measures that focus on numbers with pre-adolescents and probably more importantly, with adolescents. A focus on numbers could have ramifications on self-image and contribute to eating disorders. An alternative to clinical measures could be a focus on encouraging lifestyle habits including healthy diet and exercise skills that can be maintained throughout childhood and carry over into adulthood.
Hi Justin: I completely agree that with an adolescent population it would be ideal to focus on objective measures of lifestyle changes. I think these measures of adiposity and this study is important when we consider sports that require weight certifications (e.g., wrestling). This wasn't the intention of the authors but I think this is where it's very relevant to sports medicine.