Submitted to: Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2007
Publication Date: 2/15/2008
Citation: Shafer, K.J., Siders, W.A., Johnson, L., Lukaski, H.C. 2008. Interaction of clothing and body mass index affects validity of air displacement plethysmography in adults. Nutrition. 24(2):148-154. Interpretive Summary: Body composition assessment is important for determining health status. The Bod Pod is becoming a popular method for body composition assessment and is appealing because it is safe and non-invasive. It can also accommodate special populations, including children, the elderly, and the disabled, who may be more difficult to measure with other methods, like underwater weighing and dual x-ray absorptiometry (DXA). One concern with Bod Pod is the need for people to wear tight-fitting clothing, such as spandex or a swimsuit. These types of clothing may be uncomfortable or impractical for people with a poor body image or those who may be overweight or obese. The purpose of this study was to determine if different clothing types, like scrubs and t-shirt and shorts could be used instead of spandex by people of different shapes/body mass index (BMI) and body image concerns. A total of 132 healthy adults with normal, overweight, or obese body mass index participated in the study. Compared to the reference method, DXA, percent body fat measured while adults wore scrubs and a t-shirt and shorts, was significantly lower for adults who had a normal or overweight BMI. Percent body fat was significantly higher in spandex clothing among adults with an overweight BMI, but lower among adults with a normal BMI. Among adults with an obese BMI, percent body fat was significantly greater in spandex clothing compared to DXA; there were no differences in percent body fat in scrubs or t-shirt versus DXA. Spandex appears to be the most appropriate clothing when measuring body composition in adults who have a normal or overweight BMI. More research is needed to identify the most appropriate clothing type for adults who have an obese BMI. This research will benefit those interested in measuring body composition in the Bod Pod with individuals of various shapes and sizes.
Technical Abstract: Objective: Examine the effect of alternate clothing schemes on validity of Bod Pod to estimate percent body fat (BF) compared to dual x-ray absorptiometry (DXA), and determine if these effects differ by body mass index (BMI). Design: Cross-sectional Subjects: 132 healthy adults aged 19-81 classified by BMI as normal (N; 18.5-24.9 kg/m2 ), overweight (OW; 25-29.9 kg/m2 ) or obese (OB; 30-39.9 kg/m2) Measurements: Percent BF by DXA; percent body fat, density, and body volume by Bod Pod Results: Bod Pod derived body volume and percent BF were underestimated and body density overestimated in scrubs (SC) and t-shirt/shorts (TS) compared to spandex (SP), for each gender and BMI group (all p<.0001). Compared to DXA, BF from SC was underestimated for females (-6.3%) and males (-6.57%) and N (-11.44%) and OW (-6.76%) BMI groups (all p<.0001). Underestimation of percent BF from TS was also observed for females (-3.34%), males (-5.33%) and N (-8.63%) and OW (-4.9%) subjects (all p<.0001) compared to DXA. Percent BF was overestimated in SP for females (0.98%) (p<.0006) and males (1.46%) (p<.0001) and OW BMI group (1.19%) (p<.0006) compared to DXA, but underestimated among the N BMI group (-2.35%) (p<.0001). In the OB group, percent BF was overestimated in SP (4.8%), but was not different in SC (-0.72%; p=.10) and TS (0.54%; p=.22) versus DXA. Conclusion: SP is the preferred attire, compared to TS and SC, for valid body composition results when testing persons in the N or OW BMI range. Error in Bod Pod percent BF in the OB group was minimal in SC and TS, but concern over the effect of isothermic air on body composition estimates exists. More controlled research is warranted with OB persons to elucidate the most suitable clothing scheme and further assess the validity of Bod Pod at estimating body composition in persons with OB BMI.