THE VALIDITY OF THE TANITA?? BODY FAT MONITOR/SCALE FOR ESTIMATING PERCENT FAT

Abstract

Recently, Tanita® introduced a commercially available bioelectrical impedance (BIA) device that resembles a bathroom scale and measures both body weight and percent fat (% fat). The scale ranges in cost from $80 – $160 and the manufacturer claims that it is as accurate as more sophisticated body composition techniques, such as underwater weighing (UWW). Therefore, the purpose of the present study was to compare estimates of % fat obtained from the Tanita® scale (TAN) and skinfold (SF) equations (Σ 7 and Σ 3) to values obtained from UWW. Twenty-one inactive males (n = 7) and females (n = 14) (X age ± SD = 26 ± 7 yr, range = 19 - 50 yr, X % fat = 22.5 ± 7.7%, range = 11.8 - 39.7%) volunteered to participate. Body weight (BW) was measured with a calibrated Detecto scale to the mearest 0.11 kg. The SF measurements were taken at the triceps, subscapular, midaxillary, supcailiac, abdomen, chest, and thigh sites. Body density values were calculated using the generalized Σ 7 and Σ 3 SF equations of Jackson and Pollock (Br. J. Nutr. 40:497–504, 1978) and Jackson, Pollock and Ward (MSSE 12:175–182, 1980) for the males and females, respectively. The manufacturer did not supply the BIA equation included with the TAN. Validation analyses included examination of the constant error (CE), correlation (r), standard error of estimate (SEE) and total error (TE): (p < 0.017, Bonferroni corrected alpha 0.05/3 = 0.017)TableThe results indicated that TAN (TE = 5.3 % fat) and SF equations (Σ 7 TE = 4.9 % fat; Σ 3 TE = 5.4 % fat) resulted in TE values that were too large to be of practical value. The results for the SK's are in agreement with others who reported that the technique and these equations have limited applicability to overweight and obese individuals, which represented the majority of subjects in the present study (X % fat ± SD = 19.3 ± 5.0 % and 28.5 ± 6.9 % for the males and females, respectively). Based upon these findings, the TAN and SF techniques are not recommended for estimating % fat in males and females with average to moderately high body fatness.