title: Body fat measurement by bioelectrical impedance and air displacement plethysmography: a cross-validation study to design bioelectrical impedance equations in Mexican adults.
abstract: BACKGROUND
  The study of body composition in specific populations by techniques such as bio-impedance analysis (BIA) requires validation based on standard reference methods. The aim of this study was to develop and cross-validate a predictive equation for bioelectrical impedance using air displacement plethysmography (ADP) as standard method to measure body composition in Mexican adult men and women.
  
  
  METHODS
  This study included 155 male and female subjects from northern Mexico, 20-50 years of age, from low, middle, and upper income levels. Body composition was measured by ADP. Body weight (BW, kg) and height (Ht, cm) were obtained by standard anthropometric techniques. Resistance, R (ohms) and reactance, Xc (ohms) were also measured. A random-split method was used to obtain two samples: one was used to derive the equation by the "all possible regressions" procedure and was cross-validated in the other sample to test predicted versus measured values of fat-free mass (FFM).
  
  
  CONCLUSIONS
  The final model was: FFM (kg) = 0.7374 * (Ht2 /R) + 0.1763 * (BW) - 0.1773 * (Age) + 0.1198 * (Xc) - 2.4658. R2 was 0.97; the square root of the mean square error (SRMSE) was 1.99 kg, and the pure error (PE) was 2.96. There was no difference between FFM predicted by the new equation (48.57 +/- 10.9 kg) and that measured by ADP (48.43 +/- 11.3 kg). The new equation did not differ from the line of identity, had a high R2 and a low SRMSE, and showed no significant bias (0.87 +/- 2.84 kg).
  
  
  CONCLUSIONS
  The new bioelectrical impedance equation based on the two-compartment model (2C) was accurate, precise, and free of bias. This equation can be used to assess body composition and nutritional status in populations similar in anthropometric and physical characteristics to this sample.
authors: Centro de Investigación en Nutrición y Salud, Instituto Nacional de Salud Pública. Universidad 655, Santa Maria Ahuacatitlan, CP 62508, Cuernavaca, México. nmacias@insp.mx
authors: Nayeli
authors: N
authors: Macias
authors: Heliodoro
authors: H
authors: Alemán-Mateo
authors: Julián
authors: J
authors: Esparza-Romero
authors: Mauro E
authors: ME
authors: Valencia
mesh_terms: D000273:Adipose Tissue / Q000502:physiology*; D000328:Adult; D000886:Anthropometry / Q000379:methods*; D001823:Body Composition / Q000502:physiology; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008800:Mexico; D008875:Middle Aged; D010991:Plethysmography / Q000379:methods; D015203:Reproducibility of Results
references: Am J Clin Nutr. 1991 Jun;53(6):1345-53
references: 2035461
references: Am J Clin Nutr. 1992 Jun;55(6):1033-44
references: 1595574
references: Am J Clin Nutr. 1985 Apr;41(4):810-7
references: 3984933
references: Eur J Clin Nutr. 2007 Jul;61(7):830-6
references: 17228350
references: Eur J Clin Nutr. 2002 Mar;56(3):214-20
references: 11960296
references: Int J Obes Relat Metab Disord. 2000 Aug;24(8):1011-7
references: 10951540
references: Med Sci Sports Exerc. 1995 Dec;27(12):1692-7
references: 8614327
references: Eur J Clin Nutr. 1989 Nov;43(11):779-91
references: 2627926
references: Int J Obes Relat Metab Disord. 2003 Jul;27(7):848-55
references: 12821972
references: Lancet. 1986 Feb 8;1(8476):307-10
references: 2868172
references: Int J Obes Relat Metab Disord. 2002 Mar;26(3):389-97
references: 11896495
references: Int J Obes Relat Metab Disord. 1998 Mar;22(3):243-9
references: 9539193
references: Am J Clin Nutr. 2005 Mar;81(3):597-604
references: 15755828
references: Arterioscler Thromb Vasc Biol. 1998 Nov;18(11):1759-64
references: 9812915
references: J Appl Physiol (1985). 1986 Apr;60(4):1327-32
references: 3700310
references: Am J Clin Nutr. 1991 Mar;53(3):594-8
references: 2000812
references: Am J Clin Nutr. 2001 Jan;73(1):13-8
references: 11124743
references: Eur J Clin Nutr. 1992 Jun;46(6):419-27
references: 1639050
references: Am J Clin Nutr. 2000 Sep;72(3):694-701
references: 10966886
references: Am J Clin Nutr. 2003 Jan;77(1):71-5
references: 12499325
references: Nutrition. 2001 Mar;17(3):248-53
references: 11312069
references: Am J Clin Nutr. 1996 Sep;64(3 Suppl):428S-435S
references: 8780359
references: Int J Obes Relat Metab Disord. 1996 Dec;20(12):1081-8
references: 8968853
references: Am J Clin Nutr. 2003 Feb;77(2):331-40
references: 12540391
references: J Physiol Anthropol Appl Human Sci. 2004 Mar;23(2):35-9
references: 15067189
references: Am J Clin Nutr. 2002 Mar;75(3):453-67
references: 11864850
references: Eur J Appl Physiol. 2001 Aug;85(3-4):326-32
references: 11560087
references: Int J Obes Relat Metab Disord. 2000 Oct;24(10):1279-85
references: 11093289
references: Am J Clin Nutr. 1989 Aug;50(2):221-6
references: 2756908
references: Am J Clin Nutr. 2006 Apr;83(4):795-802
references: 16600930