title: Comparison of methods for the measurement of body composition in overweight and obese Brazilian children and adolescents before and after a lifestyle modification program.
abstract: OBJECTIVE
  To compare the body composition of overweight children and adolescents by bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) before and after physical activity program.
  
  
  METHODS
  One hundred and eleven patients with mean age (SD) of 12 (1.9) participated in the study. We assessed the weight, height, waist circumference (WC), and body composition by DXA and BIA. Patients underwent a program of diet and physical activity (1 h 30 min/day, 3 times a week for 3 months) and were evaluated before and after this period.
  
  
  RESULTS
  Mean initial zBMI were 2.3 (0.5) and waist SDS 5.9 (1.8). Significant differences were observed when we compared the measurements taken by DXA and BIA, respectively: total body fat percentage (40 and 31.5) and fat-free mass (43.1 and 50.6 kg). Regarding the trunk fat by DXA, there was a positive correlation with the WC/height ratio (r = 0.65; p < 0.01). After the intervention period, we observed a reduction in the zBMI, waist SDS, and total body fat and increase of fat-free mass by DXA. BIA only detected reduction in fat.
  
  
  CONCLUSIONS
  BIA underestimates the percentage of fat and overestimates fat-free mass in relation to DXA. There is positive correlation between trunk fat and the ratio WC/height. In addition, DXA detected changes in body composition induced by a short period of physical training, unlike BIA.
authors.affiliation: Santa Casa of São Paulo Medical School, Department of Pediatric Endocrinology, São Paulo, Brazil.
authors.forename: Arthur
authors.initials: A
authors.lastname: Lyra
authors.forename: Alexandre José
authors.initials: AJ
authors.lastname: Bonfitto
authors.forename: Vera Lucia P
authors.initials: VL
authors.lastname: Barbosa
authors.forename: Ana Cristina
authors.initials: AC
authors.lastname: Bezerra
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Longui
authors.forename: Osmar
authors.initials: O
authors.lastname: Monte
authors.forename: Cristiane
authors.initials: C
authors.lastname: Kochi
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000293:Adolescent; D001823:Body Composition / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D001938:Brazil; D002648:Child; D004032:Diet; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D009043:Motor Activity; D009765:Obesity / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy; D050177:Overweight / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000628:therapy; D055105:Waist Circumference / Q000502:physiology