title: Body composition assessment in extreme obesity and after massive weight loss induced by gastric bypass surgery.
abstract: Body composition methods were examined in 20 women [body mass index (BMI) 48.7 +/- 8.8 kg/m(2)] before and after weight loss [-44.8 +/- 14.6 (SD) kg] after gastric bypass (GBP) surgery. The reference method, a three-compartment (3C) model using body density by air displacement plethysmography and total body water (TBW) by H(2)18O dilution (3C-H(2)18O), showed a decrease in percent body fat (%BF) from 51.4 to 34.6%. Fat-free mass hydration was significantly higher than the reference value (0.738) in extreme obesity (0.756; P < 0.001) but not after weight reduction (0.747; P = 0.16). %BF by H(2)18O dilution and air displacement plethysmography differed significantly from %BF by 3C-H(2)18O in extreme obesity (P < 0.05) and 3C models using (2)H(2)O or bioelectrical impedance analysis (BIA) to determine TBW improved mean %BF estimates over most other methods at both time points. BIA results varied with the equation used, but BIA better predicted %BF than did BMI at both time points. All methods except BIA using the Segal equation were comparable to the reference method for determining changes over time. A simple 3C model utilizing air displacement plethysmography and BIA is useful for clinical evaluation in this population.
authors.affiliation: Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston 02111, USA.
authors.forename: Sai Krupa
authors.initials: SK
authors.lastname: Das
authors.forename: Susan B
authors.initials: SB
authors.lastname: Roberts
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Kehayias
authors.forename: Jack
authors.initials: J
authors.lastname: Wang
authors.forename: L K George
authors.initials: LK
authors.lastname: Hsu
authors.forename: Scott A
authors.initials: SA
authors.lastname: Shikora
authors.forename: Edward
authors.initials: E
authors.lastname: Saltzman
authors.forename: Megan A
authors.initials: MA
authors.lastname: McCrory
mesh_terms: D000273:Adipose Tissue / Q000502:physiology; D000368:Aged; D001823:Body Composition / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003720:Densitometry; D017097:Electric Impedance; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D008875:Middle Aged; D008954:Models, Biological; D009767:Obesity, Morbid / Q000473:pathology* / Q000628:therapy; D011865:Radioisotope Dilution Technique; D015431:Weight Loss / Q000502:physiology*