Comparison of a 2D iPad 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 iPad (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 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 %BFBod Pod.