Comparison of a 2D iP ad application and 3D body scanner to air displacement plethysmography for measurement of body fat percentage

Background Novel and innovative imaging methods that rapidly estimate body fat percentage (% BF ) are publicly available, yet little is known about their accuracy. The present study evaluated the test–retest reliability of a two‐dimensional iP ad (Apple, Inc., Cupertino, CA, USA) application (2D APP ) and a three‐dimensional body scanner (3D SCAN ) for estimating % BF and compared both imaging methods with air displacement plethysmography (Bod Pod; Cosmed USA, Inc., Concord, CA, USA). Methods Seventy‐nine adults (37 female, 42 male) varying widely in age [mean (SD), range] [32.9 (12.4), 18–65 years] and body mass index [25.0 (4.9), 18.2–41.8 kg m –2 ] were measured with the Bod Pod and twice with the 3D SCAN and the 2D APP in a repeated‐measures design. Results Test–retest reliability was excellent for both the 2D APP ( intraclass correlation  = 0.993) and the 3D SCAN ( intraclass correlation  = 0.993) with the SEM <1% BF for both methods. Although the three methods were highly correlated with each other ( r  =   0.857–0.923), the mean % BF estimations were significantly different ( P  =   0.001). The 2D APP [19.9 (8.2)% BF ] underestimated the Bod Pod value [21.9 (9.4)%BF] and the 3D SCAN [24.0 (6.8)%BF] overestimated. Additionally, the SE of estimate and total error exceeded 4% BF for both 2D APP and 3D SCAN , and both methods tended to overestimate lean participants and underestimate fat participants. Conclusions Although highly reliable, neither the 2D APP , nor the 3D SCAN provided valid estimates of % BF B od Pod .